Rapid characterization of physical properties for the pharmaceutical pellet cores based on NIR spectroscopy and ensemble learning

During the development of sustained-release pellets, the physical characteristics of the pellet cores can affect drug release in the preparation. The method based on near-infrared (NIR) spectroscopy and ensemble learning was proposed to swiftly assess the physical properties of the pellet cores. In the research, the potential of three algorithms, direct standardization (DS), partial least squares regression (PLSR) and generalized regression neural network (GRNN), was investigated and compared. The performance of the DS, PLSR and GRNN models were improved after applying bootstrap aggregating (Bagging) ensemble learning. And the Bagging-GRNN model showed the best predictive capacity. Except for inter-particle porosity, the mean absolute deviations of other 11 physical parameters were less than 1.0. Furthermore, the cosine coefficient values between the actual and predicted physical fingerprints was higher than 0.98 for 15 out of the 16 validation samples when using the Bagging-GRNN model. To reduce the model complexity, the 60 variables significantly correlated with angle of repose, particle size (D50) and roundness were utilized to develop the simplified Bagging-GRNN model. And the simplified model showed satisfactory predictive capacity. In summary, the developed ensemble modelling strategy based NIR spectra is a promising approach to rapidly characterize the physical properties of the pellet cores.

An evaluation of microcrystalline cellulose attributes affecting compaction-induced pellet coat damage through a multi-faceted analysis

Pellet coat damage in multi-unit pellet system (MUPS) tablets has previously been studied and addressed with limited success. The effects of lactose filler material attributes on pellet coat damage have been relatively well-studied but a similar understanding of microcrystalline cellulose (MCC) is lacking notwithstanding its high cushioning potential. Hence, the relationships between MCC attributes and pellet coat damage were investigated. Single pellet in minitablets (SPIMs) were used to isolate pellet-filler effects and reveal the under-unexplored impact of risk factors found in MUPS tablets. MUPS tablets and SPIMs were prepared with various grades of MCC and pellets with an ethylcellulose or acrylic coat at various compaction pressures. Subsequently, the extent of pellet coat damage was determined by dissolution test and quantified using two indicators to differentiate the nature of the damage. A multi-faceted analytical approach incorporated linear regression, correlations and a classification and regression tree algorithm and evaluated how MCC attributes, such as flowability, particle size and plastic deformability, exert various influences on the extent of ethylcellulose and acrylic pellet coat damage. This analysis improved the understanding of the different mechanisms by which pellet coat damage to these two polymer types occurs which can help enhance future pellet coat damage mitigation strategies.

Pharmacodynamics and pharmacokinetics of PLGA-based doxorubicin-loaded implants for tumor therapy

The traditional systemic chemotherapy through intravenous infusion of doxorubicin (DOX) has many side effects. The aim of this study was to develop a PLGA-based DOX-loaded implant and to evaluate the efficacy and drug metabolism distribution of the implant in intratumoral chemotherapy for osteosarcoma (OS). In this study, implants containing DOX, poly(d,l-lactide-co-glycolide), and polyethylene glycol 4000 were prepared by melt-molding method. Then, the antitumor activity and systemic drug distribution of the implants were tested in a K7M2 OS bearing mouse model. The scanning electron microscope images showed that DOX was uniformly dispersed in the polymer matrix. Both the in vitro and in vivo release profiles of implants are characterized by three-phase release. Implantation of DOX-loaded implants into tumors can inhibit tumor growth in a dose-dependent manner. The pharmacokinetic behavior shows that intratumor chemotherapy through implants has a much higher drug concentration in tumors than in normal tissues, which may be the reason for improving antitumor activity and reducing systemic side effects. In summary, the drug release of the implants prepared in this study is sustained and stable, which promotes long-term local accumulation of drugs in tumors, improves the efficacy of chemotherapy and has low toxicity to normal tissues.

Cortisol regulates insulin-like growth-factor binding protein (igfbp) gene expression in Atlantic salmon parr

The growth hormone (Gh)/insulin-like growth-factor (Igf)/Igf binding protein (Igfbp) system regulates growth and osmoregulation in salmonid fishes, but how this system interacts with other endocrine systems is largely unknown. Given the well-documented consequences of mounting a glucocorticoid stress response on growth, we hypothesized that cortisol inhibits anabolic processes by modulating the expression of hepatic igfbp mRNAs. Atlantic salmon (Salmo salar) parr were implanted intraperitoneally with cortisol implants (0, 10, and 40 μg g^-1 body weight) and sampled after 3 or 14 days. Cortisol elicited a dose-dependent reduction in specific growth rate (SGR) after 14 days. While plasma Gh and Igf1 levels were unchanged, hepatic igf1 mRNA was diminished and hepatic igfbp1b1 and -1b2 were stimulated by the high cortisol dose. Plasma Igf1 was positively correlated with SGR at 14 days. Hepatic gh receptor (ghr), igfbp1a, -2a, -2b1, and -2b2 levels were not impacted by cortisol. Muscle igf2, but not igf1 or ghr, levels were stimulated at 3 days by the high cortisol dose. As both cortisol and the Gh/Igf axis promote seawater (SW) tolerance, and particular igfbps respond to SW exposure, we also assessed whether cortisol coordinates the expression of branchial igfbps and genes associated with ion transport. Cortisol stimulated branchial igfbp5b2 levels in parallel with Na⁺/K⁺-ATPase (NKA) activity and nka-α1b, Na⁺/K⁺/2Cl^--cotransporter 1 (nkcc1), and cystic fibrosis transmembrane regulator 1 (cftr1) mRNA levels. The collective results indicate that cortisol modulates the growth of juvenile salmon via the regulation of hepatic igfbp1s whereas no clear links between cortisol and branchial igfbps previously shown to be salinity-responsive could be established.

Clinically established biodegradable long acting injectables: An industry perspective

Long acting injectable formulations have been developed to sustain the action of drugs in the body over desired periods of time. These delivery platforms have been utilized for both systemic and local drug delivery applications. This review gives an overview of long acting injectable systems that are currently in clinical use. These products are categorized in three different groups: biodegradable polymeric systems, including microparticles and implants; micro and nanocrystal suspensions and oil-based formulations. Furthermore, the applications of these drug delivery platforms for the management of various chronic diseases are summarized. Finally, this review addresses industrial challenges regarding the development of long acting injectable formulations.

Lymphatic immunomodulation using engineered drug delivery systems for cancer immunotherapy

Though immunotherapy has revolutionized the treatment of cancer to improve disease outcomes, an array of challenges remain that limit wider clinical success, including low rate of response and immune-related adverse events. Targeting immunomodulatory drugs to therapeutically relevant tissues offers a way to overcome these challenges by potentially enabling enhanced therapeutic efficacy and decreased incidence of side effects. Research highlighting the importance of lymphatic tissues in the response to immunotherapy has increased interest in the application of engineered drug delivery systems (DDSs) to enable specific targeting of immunomodulators to lymphatic tissues and cells that they house. To this end, a variety of DDS platforms have been developed that enable more efficient uptake into lymphatic vessels and lymph nodes to provide targeted modulation of the immune response to cancer. This can occur either by delivery of immunotherapeutics to lymphatics tissues or by direct modulation of the lymphatic vasculature itself due to their direct involvement in tumor immune processes. This review will highlight DDS platforms that, by enabling the activities of cancer vaccines, chemotherapeutics, immune checkpoint blockade (ICB) antibodies, and anti- or pro-lymphangiogenic factors to lymphatic tissues through directed delivery and controlled release, augment cancer immunotherapy.

Vastly extended drug release from poly(pro-17β-estradiol) materials facilitates in vitro neurotrophism and neuroprotection

Central nervous system (CNS) injuries persist for years, and currently there are no therapeutics that can address the complex injury cascade that develops over this time-scale. 17β-estradiol (E2) has broad tropism within the CNS, targeting and inducing beneficial phenotypic changes in myriad cells following injury. To address the unmet need for vastly prolonged E2 release, we report first-generation poly(pro-E2) biomaterial scaffolds that release E2 at nanomolar concentrations over the course of 1-10 years via slow hydrolysis in vitro. As a result of their finely tuned properties, these scaffolds demonstrate the ability to promote and guide neurite extension ex vivo and protect neurons from oxidative stress in vitro. The design and testing of these materials reported herein demonstrate the first step towards next-generation implantable biomaterials with prolonged release and excellent regenerative potential.

Promising Approach in the Treatment of Glaucoma Using Nanotechnology and Nanomedicine-Based Systems

Glaucoma is considered a leading cause of blindness with the human eye being one of the body's most delicate organs. Ocular diseases encompass diverse diseases affecting the anterior and posterior ocular sections, respectively. The human eye's peculiar and exclusive anatomy and physiology continue to pose a significant obstacle to researchers and pharmacologists in the provision of efficient drug delivery. Though several traditional invasive and noninvasive eye therapies exist, including implants, eye drops, and injections, there are still significant complications that arise which may either be their low bioavailability or the grave ocular adverse effects experienced thereafter. On the other hand, new nanoscience technology and nanotechnology serve as a novel approach in ocular disease treatment. In order to interact specifically with ocular tissues and overcome ocular challenges, numerous active molecules have been modified to react with nanocarriers. In the general population of glaucoma patients, disease growth and advancement cannot be contained by decreasing intraocular pressure (IOP), hence a spiking in future research for novel drug delivery systems and target therapeutics. This review focuses on nanotechnology and its therapeutic and diagnostic prospects in ophthalmology, specifically glaucoma. Nanotechnology and nanomedicine history, the human eye anatomy, research frontiers in nanomedicine and nanotechnology, its imaging modal quality, diagnostic and surgical approach, and its possible application in glaucoma will all be further explored below. Particular focus will be on the efficiency and safety of this new therapy and its advances.

Film interface for drug testing for delivery to cells in culture and in the brain

Brain access remains a major challenge in drug testing. The nearly 'impermeable' blood-brain-barrier (BBB) prevents most drugs from gaining access to brain cells via systematic intravenous (IV) injection. In this study, silk fibroin films were used as drug carrier as well as cell culture substrate to simulate the in vivo interface between drug reservoir and brain cells for testing drug delivery in the brain. In in vitro studies, film-released arabinofuranosyl cytidine (AraC), a mitotic inhibitor, selectively killed glial cells in film-supported mixed neural cell cultures; with widened dosage windows for drug efficacy and tolerance compared to drugs in solution. In the brain, the presence of silk films was well tolerated with no signs of acute neuroinflammation, cell death, or altered brain function. Topical application of silk films on the cortical surface delivered Evans blue, a BBB-impenetrable fluorescent marker, through the intact dura matter into the parenchyma of the ipsilateral hemisphere as deep as the hippocampal region, but not the contralateral hemisphere. In a mouse traumatic brain injury (TBI) model, necrosis markers by film delivery accessed more cells in the lesion core than by con-current IV delivery; whereas the total coverage including the peri-lesional area appeared to be comparable between the two routes. The complementary distribution patterns of co-delivered markers provided direct evidence of the partial confinement of either route's access to brain cells by a restrictive zone near the lesion border. Finally, film-delivered necrostatin-1 reduced overall cell necrosis by approximately 40% in the TBI model. These findings from representative small molecules of delivery route-dependent drug access are broadly applicable for evaluating drug actions both in vitro and in vivo. Combined with its demonstrated role of supporting neuron-electrode interfaces, the film system can be further developed for testing a range of neuromodulation approaches (i.e., drug delivery, electrical stimulation, cell graft) in the brain. STATEMENT OF SIGNIFICANCE: This study demonstrated that silk fibroin films can be used to evaluate drug actions both in vitro and in vivo, partially overcoming the significant delivery barriers of the brain. This system can be adapted for efficient drug access to specific brain regions and/or cell types. The film system can be further developed for testing a range of interventions with drugs, electrical signals or cell graft for analysis of treatment outcomes including cell responses and brain function.

In vivo analysis of a first-in-class tri-alkyl norspermidine-biaryl antibiotic in an active release coating to reduce the risk of implant-related infection

Prosthetic joint infection (PJI) is a well-known and persisting problem. Active release coatings have promise to provide early protection to an implant by eradicating small colony biofilm contaminants or planktonic bacteria that can form biofilm. Traditional antibiotics can be limited as active release agents in that they have limited effect against biofilms and develop resistance at sub-lethal concentrations. A unique first-in-class compound (CZ-01127) was assessed as the active release agent in a silicone (Si)-based coating to prevent PJI in a sheep model of joint space infection. Titanium (Ti) plugs contained a porous coated Ti (PCTi) region and polymer-coated region. Plugs were implanted into a femoral condyle of sheep to assess the effect of the Si polymer on cancellous bone ingrowth, the effect of CZ-01127 on bone ingrowth, and the ability of CZ-01127 to prevent PJI. Microbiological results showed that CZ-01127 was able to eradicate bacteria in the local region of the implanted plugs. Data further showed that Si did not adversely affect bone ingrowth. However, bacteria that reached the joint space (synovium) were not fully eradicated. Outcomes suggested that the CZ-01127 coating provided local protection to the implant system in a challenging model, the design of which could be beneficial for testing future antimicrobial therapies for PJI. STATEMENT OF SIGNIFICANCE: Periprosthetic joint infection (PJI) is now commonplace, and constitutes an underlying problem that patients and physicians face. Active release antibiotic coatings have potential to prevent these infections. Traditional antibiotics are limited in their ability to eradicate bacteria that reside in biofilms, and are more susceptible to resistance development. This study addressed these limitations by testing the efficacy of a unique antimicrobial compound in a coating that was tested in a challenging sheep model of PJI. The unique coating was able to eradicate bacteria and prevent infection in the environment adjacent to the implant. Bacteria that escaped into the joint space still caused infection, yet benchmark data can be used to optimize the coating and translate it toward clinical use.

Mesoporous bioactive glass/ɛ-polycaprolactone scaffolds promote bone regeneration in osteoporotic sheep

Macroporous scaffolds made of a SiO2-CaO-P2O5 mesoporous bioactive glass (MBG) and ɛ-polycaprolactone (PCL) have been prepared by robocasting. These scaffolds showed an excellent in vitro biocompatibility in contact with osteoblast like cells (Saos 2) and osteoclasts derived from RAW 264.7 macrophages. In vivo studies were carried out by implantation into cavitary defects drilled in osteoporotic sheep. The scaffolds evidenced excellent bone regeneration properties, promoting new bone formation at both the peripheral and the inner parts of the scaffolds, thick trabeculae, high vascularization and high presence of osteoblasts and osteoclasts. In order to evaluate the effects of the local release of an antiosteoporotic drug, 1% (%wt) of zoledronic acid was incorporated to the scaffolds. The scaffolds loaded with zoledronic acid induced apoptosis in Saos 2 cells, impeded osteoclast differentiation in a time dependent manner and inhibited bone healing, promoting an intense inflammatory response in osteoporotic sheep. STATEMENT OF SIGNIFICANCE: In addition to an increase in bone fragility and susceptibility to fracture, osteoporosis also hinders the clinical success of endosseous implants and grafting materials for the treatment of bone defects. For the first time, macroporous scaffolds made of mesoporous bioactive glass and ε-caprolactone have been evaluated in a sheep model that mimics the osteoporosis conditions in humans. These implants fostered bone regeneration, promoting new bone formation at both the peripheral and the inner parts of the scaffolds, showing thick trabeculae and a high vascularization degree. Our results indicate that macroporous structures containing highly bioactive mesoporous glasses could be excellent candidates for the regenerative treatment of bone defects in osteoporotic patients.

Silk Protein Bioresorbable, Drug-Eluting Ear Tubes: Proof-of-Concept

Otitis media with effusion (OEM) is a common pediatric pathology treated with topical fluoroquinolones (ear drops) and tympanoplasty tube, also referred to as ear tube, implantation for middle ear drainage. Commercially available ear tubes are fabricated using poly (lactic-co-glycolic acid) synthetic materials that are associated with long-complications due to premature extrusion. Resorbable materials have emerged as desirable alternatives to reduce extrusion-related complications, but often limited by fast resorption rates. Therefore, resorbable tubes with long-term functional integrity are required for future clinical translation. In this communication, a proof-of-concept study is reported on a bioresorbable and drug-eluting silk ear tube device. Preliminary in vitro assessments reveal time-dependent drug elution and antimicrobial properties, while maintaining long-term functional integrity in vivo. This report provides evidence of a silk ear tube with potential for future clinical translation and OEM treatment.

Electrospun Patch Functionalized with Nanoparticles Allows for Spatiotemporal Release of VEGF and PDGF-BB Promoting In Vivo Neovascularization

The use of nanomaterials as carriers for the delivery of growth factors has been applied to a multitude of applications in tissue engineering. However, issues of toxicity, stability, and systemic effects of these platforms have yet to be fully understood, especially for cardiovascular applications. Here, we proposed a delivery system composed of poly(dl-lactide- co-glycolide) acid (PLGA) and porous silica nanoparticles (pSi) to deliver vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF). The tight spatiotemporal release of these two proteins has been proven to promote neovascularization. In order to minimize tissue toxicity, localize the release, and maintain a stable platform, we conjugated two formulations of PLGA-pSi to electrospun (ES) gelatin to create a combined ES patch releasing both PDGF and VEGF. When compared to freely dispersed particles, the ES patch cultured in vitro with neonatal cardiac cells had significantly less particle internalization (2.0 ± 1.3%) compared to free PLGA-pSi (21.5 ± 6.1) or pSi (28.7 ± 2.5) groups. Internalization was positively correlated to late-stage apoptosis with PLGA-pSi and pSi groups having increased apoptosis compared to the untreated group. When implanted subcutaneously, the ES patch was shown to have greater neovascularization than controls evidenced by increased expression of α-SMA and CD31 after 21 days. Quantitative reverse transcription-polymerase chain reaction results support increased angiogenesis by the upregulation of VEGFA, VEGFR2, vWF, and COL3A1, exhibiting a synergistic effect with the release of VEGF-A164 and PDGF-BB after 21 days in vivo. The results of this study proved that the ES patch reduced cellular toxicity and may be tailored to have a dual release of growth factors promoting localized neovascularization.

Resveratrol Delivery from Porous Poly(lactide- co-glycolide) Scaffolds Promotes an Anti-Inflammatory Environment within Visceral Adipose Tissue

As biomaterial therapies emerge to address adipose tissue dysfunction that underlies metabolic disease, the immune response to these systems must be established. As a potential therapy, we are investigating resveratrol delivery from porous poly(lactide- co-glycolide) scaffolds designed to integrate with adipose tissue. Resveratrol was selected for its ability to protect mice and primates from high fat diet and broad anti-inflammatory properties. Herein, we report fabrication of scaffolds with high resveratrol loading that are stable and active for up to one year. In vitro release profiles indicate that drug release is biphasic with a burst release over 3 days followed by a plateau. Surprisingly, we find that PLG scaffolds implanted into adipose tissue of mice promote an anti-inflammatory environment characterized by high arginase-1 and low TNF-α and IL-6 compared to naïve unmanipulated fat. Resveratrol delivery from the scaffold augments this anti-inflammatory environment by decreasing monocyte and lymphocyte numbers at the implant site and increasing expression of IL-10 and IL-13, cytokines that promote healthy adipose tissue. In terms of therapeutic applications, implant of scaffolds designed to release resveratrol into the visceral fat decreases MCP-1 expression in mice fed a high fat diet, a molecule that drives both local and systemic inflammation during obesity. Taken together, resveratrol delivery to adipose tissue using poly(lactide- co-glycolide) scaffolds is a promising therapeutic strategy for the treatment of adipose tissue inflammation that drives metabolic disease.

Locally Deployable Nanofiber Patch for Sequential Drug Delivery in Treatment of Primary and Advanced Orthotopic Hepatomas

With unsatisfactory effects of systemic chemotherapy for treatment of unresectable or advanced hepatoma, local and sustained delivery of chemotherapeutic agents is becoming a promising solution. The in situ administered platforms increase the drug concentrations in tumor regions, decrease the side effects to organs, prevent the damage to vascular endothelium, and reduce the frequency of drug administration. The prevalent strategy based on minimally invasive transarterial chemoembolization oftentimes induces upper gastrointestinal hemorrhage, liver failure, and liver abscess. In addition, integrating various antitumor drugs in one platform, especially the drugs with different hydrophilic/hydrophobic properties, and achieving sustained and/or sequential release profiles to synergistically inhibit cancer progression remain challenging. In this study, a local drug delivery system made of an emulsion-electrospun polymer patch was developed, which contained hydrophobic 10-hydroxycamptothecin (HCPT) and hydrophilic tea polyphenols (TP) in the shell and core of the nanofiber, respectively. Due to this core-sheath structure, HCPT and TP exhibited sustained and sequential releases first with HCPT followed by TP. HCPT was used to suppress the proliferation and malignant transformation of hepatoma, whereas TP was aimed to decrease the levels of oxygen free radicals and further prevent the invasion and metastasis of tumor cells. Our study presented the potential superiority of this class of core-sheath structured nanofiber membranes in localized treatment of both primary and advanced orthotopic hepatomas.

Patient-Specific Bioinks for 3D Bioprinting of Tissue Engineering Scaffolds

Bioprinting has emerged as a promising tool in tissue engineering and regenerative medicine. Various 3D printing strategies have been developed to enable bioprinting of various biopolymers and hydrogels. However, the incorporation of biological factors has not been well explored. As the importance of personalized medicine is becoming more clear, the need for the development of bioinks containing autologous/patient-specific biological factors for tissue engineering applications becomes more evident. Platelet-rich plasma (PRP) is used as a patient-specific source of autologous growth factors that can be easily incorporated to hydrogels and printed into 3D constructs. PRP contains a cocktail of growth factors enhancing angiogenesis, stem cell recruitment, and tissue regeneration. Here, the development of an alginate-based bioink that can be printed and crosslinked upon implantation through exposure to native calcium ions is reported. This platform can be used for the controlled release of PRP-associated growth factors which may ultimately enhance vascularization and stem cell migration.

Injectable drug depot engineered to release multiple ophthalmic therapeutic agents with precise time profiles for postoperative treatment following ocular surgery

A multi-drug delivery platform is developed to address current shortcomings of post-operative ocular drug delivery. The sustained biodegradable drug release system is composed of biodegradable polymeric microparticles (MPs) incorporated into a bulk biodegradable hydrogel made from triblock copolymers with poly(ethylene glycol) (PEG) center blocks and hydrophobic biodegradable polyester blocks such as poly(lactide-co-glycolide) (PLGA), Poly(lactic acid) (PLA), or Poly(lactide-co-caprolactone) (PLCL) blocks. This system is engineered to flow as a liquid solution at room temperature for facile injection into the eye and then quickly gel as it warms to physiological body temperatures (approximately 37 °C). The hydrogel acts as an ocular depot that can release three different drug molecules at programmed rates and times to provide optimal release of each species. In this manuscript, the hydrogel is configured to release a broad-spectrum antibiotic, a potent corticosteroid, and an ocular hypotensive, three ophthalmic therapeutic agents that are essential for post-operative management after ocular surgery, each drug released at its own timescale. The delivery platform is designed to mimic current topical application of postoperative ocular formulations, releasing the antibiotic for up to a week, and the corticosteroid and the ocular hypotensive agents for at least a month. Hydrophobic blocks, such as PLCL, were utilized to prolong the release duration of the biomolecules. This system also enables customization by being able to vary the initial drug loading to linearly tune the drug dose released, while maintaining a constant drug release profile over time. This minimally invasive biodegradable multi-drug delivery system is capable of replacing a complex ocular treatment regimen with a simple injection. Such a depot system has the potential to increase patient medication compliance and reduce both the immediate and late term complications following ophthalmic surgery.

STATEMENT OF SIGNIFICANCE

After ocular surgery, patients routinely receive multiple medications including antibiotics, steroids and ocular hypotensives to ensure optimal surgical outcomes. The current standard of care for postoperative treatment after ocular surgery involves using eye drops daily, which has limited effectiveness mainly due to poor patient adherence. To improve patient experience and outcomes, this article presents the first thermoresponsive hydrogel able to release multiple drug molecules for the application of post-operative treatment following ocular surgery. By varying the parameters such as hydrogel type and polymer hydrophobicity, the drug release profile, duration and dosage can finely be tuned. The approach presented in this article can readily be applied to other applications by simply changing the drug loaded in the drug delivery system.

Nanohybrid Electro-Coatings Toward Therapeutic Implants with Controlled Drug Delivery Potential for Bone Regeneration

Coatings of metallic implants facilitate a new bioactive interface that favors osteogenic responses and bone formation. Providing a therapeutic capacity to the coatings, involving with a sustainable and controllable delivery of drug molecules, significantly improves the bone regenerative potential. Here we design a novel nanocomposite coating, made of mesoporous silica-shelled hydroxyapatite (MS-HA) nanoparticles and chitosan (Chi), incorporating osteogenic drug dexamethasone phosphate (Dex(P)) within the MS-HA, by the process of an electrophoretic deposition (EPD). MS-HA, produced by a sol–gel reaction of silica onto an HA nanorod, exhibited mono-dispersed core–shell nanoparticles with a size of ∼40 nm and a shell thickness of ∼25 nm. The highly mesoporous structure enabled an effective loading of Dex(P) onto the nanocarriers, showing a loading capacity as high as 15% by weight. The Dex(P) loaded MS-HA were homogenized with Chi in acidic ethanol/water to allow for the EPD process. Nanocomposite coatings were produced well, forming thicknesses a few micrometers largely tunable with EPD parameters and exhibiting MS-HA nanoparticles evenly distributed within Chi matrix. While Dex(P) release from the bare MS-HA nanocarrier was very abrupt, showing a complete release within 24 h, the Dex(P) release from the nanocomposite coatings profiled a highly sustainable pattern over a month. Rat mesenchymal stem cells cultured on the Dex(P)-releasing coatings were substantially stimulated to an osteoblastic lineage, presenting enhanced alkaline phosphate activity and higher levels of osteogenic genes, with respect to coatings free of Dex(P). An indirect culture test also confirmed the long-term release effects of Dex(P) from the coatings over 4 weeks. The currently-developed nanocomposite EPD coatings, with a capacity to load osteogenic drug at large quantity and to deliver for a long-term period, are considered as a promising therapeutic coating platform for metallic bone implants.

Novel Synthesized Nanofibrous Scaffold Efficiently Delivered hBMP-2 Encoded in Adenoviral Vector to Promote Bone Regeneration

Treatment of bone defect, especially large bone defect, is still a challenge for physicians clinically. Bone morphogenetic protein 2 (BMP-2) can induce osteoblast differentiation and promote new bone formation. Recently, nanomaterials have been widely used as a carrier to hold and deliver biomolecules, like human bone morphogenetic protein 2 gene (hBMP-2) in target cells/tissues. Most nanomethods, however, need further modification in order to work more reliably in clinical applications. Therefore, in this study, we created a novel poly(lactic-co-glycolic acid [PLGA]) nanofibrous scaffold using an electrospinning technique; then, using a lyophilization process to allow nanofibrous scaffold to adsorb hBMP-2 adenoviral vector, AdCMV-hBMP2. Results indicate that the lyophilized poly(lactic-co-glycolic acid) nanofibrous scaffold/AdCMVhBMP2 can efficiently release and transduce cells in vitro and in vivo, and secrete functional hBMP-2 to promote osteogenic differentiation in vitro, and new bone generation in vivo. Importantly, the amount of newly formed bone covered >80% of the bone defect area 8 weeks post-implantation in vivo, in which the defect could not be repaired without any treatment in general. Our data demonstrate that the lyophilized PLGA nanofibrous scaffold/AdCMV-hBMP2 created herein stably and efficiently release functional viral vector to transduce local cells, resulting in secretion of hBMP-2 and promote new bone formation in vivo. Our new nanodelivery method has potential clinical application for the repair of large bone defects.

Biodegradable Self-Assembled Micelles Based on MPEG-PTMC Copolymers: An Ideal Drug Delivery System for Vincristine

Despite advantageous properties, micelles using methoxy poly(ethylene glycol)-poly(trimethylene carbonate) (MPEGPTMC) have not been widely studied. In this work, we aim to develop a novel vehicle for vincristine (VCR) based on a MPEG-PTMC micelle system. MPEG-PTMC with a series of molecular weights were synthesized and screened for the appropriate range for forming stable VCR micelles. The prepared micelles were then characterized in vitro and in vivo . VCR micelles presented high stability and ideal sustained release profile. The passive targeting effect was also enhanced compared with liposomal VCR. These results provide critical data to give the first clues regarding novel VCR micelles which exhibit potential for clinical application.

Foreign Body Reaction to Biomaterial Nanotubular Surface and the Influence of Silver Loading

The impacts of biomaterial surface properties (i.e., surface nanotopography) and dopants (i.e., silver (Ag)) on the biomaterial-associated foreign body reaction (FBR) remain unclear. In this study, an in vivo FBR that was induced by a titania nanotube array (NT) on titanium was examined with and without Ag loading. An NT with an 80 nm diameter that was fabricated by anodization, and the NT samples that were loaded with two Ag concentrations (NT-AgH and NT-AgL) and formed by electrodeposition exhibited high hydrophilicities. A relatively rapid initial Ag+ release with a subsequent gradual reduction was observed for NT-AgH and NT-AgL; the Ag+ release was higher for NT-AgH than for NT-AgL. We found that the NT decreased the biomaterial-associated FBR, evidenced by a decreased fibrous capsule thickness and a number of recruited macrophages. The effect of Ag loading on the FBR was considered acceptable because the FBR induced by the NT-Ag samples was still less severe than that of the PT control. Additionally, the temporary increases in the blood, brain, liver and kidney Ag+ concentrations did not produce general side effects and were considered to be in the safe range. This study demonstrates the ability of nanotopography to alleviate the biomaterial-associated FBR and provides further evidence for future clinical applications of biomaterials with nanostructures and Ag loading.

In situ depot formation of anti-HIV fusion-inhibitor peptide in recombinant protein polymer hydrogel

Most peptide drugs have short half-lives, necessitating frequent injections that may induce skin sensitivity reactions; therefore, versatile prolonged-release delivery platforms are urgently needed. Here, we focused on an oxidatively and thermally responsive recombinant elastin-like polypeptide with periodic cysteine residues (cELP), which can rapidly and reversibly form a disulfide cross-linked network in which peptide can be physically incorporated. As a model for proof of concept, we used enfuvirtide, an antiretroviral fusion-inhibitor peptide approved for treatment of human immunodeficiency virus (HIV) infection. cELP was mixed with enfuvirtide and a small amount of hydrogen peroxide (to promote cross-linking), and the soluble mixture was injected subcutaneously. The oxidative cross-linking generates a network structure, causing the mixture to form a hydrogel in situ that serves as an enfuvirtide depot. We fabricated a series of enfuvirtide-containing hydrogels and examined their stability, enfuvirtide-releasing profile and anti-HIV potency in vitro. Among them, hydrophobic cELP hydrogel provided effective concentrations of enfuvirtide in blood of rats for up to 8 h, and the initial concentration peak was suppressed compared with that after injection of enfuvirtide alone. cELP hydrogels should be readily adaptable as platforms to provide effective depot systems for delivery of other anti-HIV peptides besides enfuvirtide.

STATEMENT OF SIGNIFICANCE

In this paper, we present an anti-HIV peptide delivery system using oxidatively and thermally responsive polypeptides that contain multiple periodic cysteine residues as an injectable biomaterial capable of in situ self-gelation, and we demonstrate its utility as an injectable depot capable of sustained release of anti-HIV peptides. The novelty of this work stems from the platform employed to provide the depot encapsulating the peptide drugs (without chemical conjugation), which consists of rationally designed, genetically engineered polypeptides that enable the release rate of the peptide drugs to be precisely controlled.

In-situ tissue regeneration through SDF-1α driven cell recruitment and stiffness-mediated bone regeneration in a critical-sized segmental femoral defect

In-situ tissue regeneration aims to utilize the body's endogenous healing capacity through the recruitment of host stem or progenitor cells to an injury site. Stromal cell-derived factor-1α (SDF-1α) is widely discussed as a potent chemoattractant. Here we use a cell-free biomaterial-based approach to (i) deliver SDF-1α for the recruitment of endogenous bone marrow-derived stromal cells (BMSC) into a critical-sized segmental femoral defect in rats and to (ii) induce hydrogel stiffness-mediated osteogenic differentiation in-vivo. Ionically crosslinked alginate hydrogels with a stiffness optimized for osteogenic differentiation were used. Fast-degrading porogens were incorporated to impart a macroporous architecture that facilitates host cell invasion. Endogenous cell recruitment to the defect site was successfully triggered through the controlled release of SDF-1α. A trend for increased bone volume fraction (BV/TV) and a significantly higher bone mineral density (BMD) were observed for gels loaded with SDF-1α, compared to empty gels at two weeks. A trend was also observed, albeit not statistically significant, towards matrix stiffness influencing BV/TV and BMD at two weeks. However, over a six week time-frame, these effects were insufficient for bone bridging of a segmental femoral defect. While mechanical cues combined with ex-vivo cell encapsulation have been shown to have an effect in the regeneration of less demanding in-vivo models, such as cranial defects of nude rats, they are not sufficient for a SDF-1α mediated in-situ regeneration approach in segmental femoral defects of immunocompetent rats, suggesting that additional osteogenic cues may also be required.

STATEMENT OF SIGNIFICANCE

Stromal cell-derived factor-1α (SDF-1α) is a chemoattractant used to recruit host cells for tissue regeneration. The concept that matrix stiffness can direct mesenchymal stromal cell (MSC) differentiation into various lineages was described a decade ago using in-vitro experiments. Recently, alginate hydrogels with an optimized stiffness and ex-vivo encapsulated MSCs were shown to have an effect in the regeneration of skull defects of nude rats. Here, we apply this material system, loaded with SDF-1α and without encapsulated MSCs, to (i) recruit endogenous cells and (ii) induce stiffness-mediated osteogenic differentiation in-vivo, using as model system a load-bearing femoral defect in immunocompetent rats. While a cell-free approach is of great interest from a translational perspective, the current limitations are described.

A Facile and Versatile Method to Endow Biomaterial Devices with Zwitterionic Surface Coatings

The surface modification of implantable biomaterials with zwitterionic phosphorylcholine polymer is demonstrated through mussel-mimetic catecholamine polymer thin films. Using this method, the surfaces of alginate hydrogel microspheres and polystyrene microbeads, a model material known to produce robust foreign body responses and fibrosis, are successfully modified to reduce the tissue reaction by reducing the fibrosis in immunocompetent C57BL/6J mice.

Advanced surface chemical analysis of continuously manufactured drug loaded composite pellets

The aim of the present study was to develop and characterise polymeric composite pellets by means of continuous melt extrusion techniques. Powder blends of a steroid hormone (SH) as a model drug and either ethyl cellulose (EC N10 and EC P7 grades) or hydroxypropyl methylcellulose (HPMC AS grade) as polymeric carrier were extruded using a Pharma 11mm twin screw extruder in a continuous mode of operation to manufacture extruded composite pellets of 1mm length. Molecular modelling study using commercial Gaussian 09 software outlined a possible drug-polymer interaction in the molecular level to develop solid dispersions of the drug in the pellets. Solid-state analysis conducted via a differential scanning calorimetry (DSC), hot stage microscopy (HSM) and X-ray powder diffraction (XRPD) analyses revealed the amorphous state of the drug in the polymer matrices. Surface analysis using SEM/energy dispersive X-ray (EDX) of the produced pellets arguably showed a homogenous distribution of the C and O atoms in the pellet matrices. Moreover, advanced chemical surface analysis conducted via atomic force microscopy (AFM) showed a homogenous phase system having the drug molecule dispersed onto the amorphous matrices while Raman mapping confirmed the homogenous single-phase drug distribution in the manufactured composite pellets. Such composite pellets are expected to deliver multidisciplinary applications in drug delivery and medical sciences by e.g. modifying drug solubility/dissolutions or stabilizing the unstable drug (e.g. hormone, protein) in the composite network.

Mediating bone regeneration by means of drug eluting implants: From passive to smart strategies

In addition to excellent biocompatibility and mechanical performance, the new generation of bone and craniofacial implants are expected to proactively contribute to the regeneration process and dynamically interact with the host tissue. To this end, integration and sustained delivery of therapeutic agents has become a rapidly expanding area. The incorporated active molecules can offer supplementary features including promoting oteoconduction and angiogenesis, impeding bacterial infection and modulating host body reaction. Major limitations of the current practices consist of low drug stability overtime, poor control of release profile and kinetics as well as complexity of finding clinically appropriate drug dosage. In consideration of the multifaceted cascade of bone regeneration process, this research is moving towards dual/multiple drug delivery, where precise control on simultaneous or sequential delivery, considering the possible synergetic interaction of the incorporated bioactive factors is of utmost importance. Herein, recent advancements in fabrication of synthetic load bearing implants equipped with various drug delivery systems are reviewed. Smart drug delivery solutions, newly developed to provide higher tempo-spatial control on the delivery of the pharmaceutical agents for targeted and stimuli responsive delivery are highlighted. The future trend of implants with bone drug delivery mechanisms and the most common challenges hindering commercialization and the bench to bedside progress of the developed technologies are covered.

Formulation and Coating of Alginate and Alginate-Hydroxypropylcellulose Pellets Containing Ranolazine

The formulation and the coating composition of biopolymeric pellets containing ranolazine were studied to improve their technological and biopharmaceutical properties. Eudragit L100 (EU L100) and Eudragit L30 D-55-coated alginate and alginate-hydroxypropylcellulose (HPC) pellets were prepared by ionotropic gelation using 3 concentrations of HPC (0.50%, 0.65%, and 1.00% wt/wt) and applying different percentages (5%, 10%, 20%, and 30% wt/wt) of coating material. The uncoated pellets were regular in shape and had mean diameter between 1490 and 1570 μm. The rate and the entity of the swelling process were affected by the polymeric composition: increasing the HPC concentration, the structure of the pellets became more compact and slowed down the penetration of fluids. Coated alginate-HPC formulations were able to control the drug release at neutral pH: a higher quantity of HPC in the system determined a slower release of the drug. The nature of the coating polymer and the coating level applied affected the drug release in acidic environment: EU L100 gave better performance than Eudragit L30 D-55 and the best coating level was 20%. The pellets containing 0.65% of HPC and coated with 20% EU L100 represented the best formulation, able to limit the drug release in acidic environment and to control it at pH 6.8.

Beeswax corticosterone implants produce long-term elevation of plasma corticosterone and influence condition

Glucocorticoids can play a critical role in modulating life-history trade-offs. However, studying the effects of glucocorticoids on life-history often requires experimentally elevating plasma glucocorticoid concentrations for several weeks within normal physiological limits and without repeated handling of the animal. Recently, implants made of beeswax and testosterone (T) were shown to have release dynamics superior to some currently available T implants, and these beeswax implants dissolved, eliminating the need to recapture the animal. We evaluated the utility of beeswax implants containing four different dosages of corticosterone (CORT; the primary glucocorticoid in birds) and their effect on several condition indices in a captive colony of zebra finches (Taeniopygia guttata). The three implants with the greatest CORT doses (0.05, 0.1, and 0.5mg) produced spikes in plasma CORT concentrations 20h after treatment, but were within the limits that zebra finches may normally experience. The 0.5mg CORT implant elevated plasma CORT between typical baseline and restraint stress levels reported in other studies of zebra finches for the entire 35day experiment. Birds in the 0.5mg implant group were heavier, had greater furcular fat scores, and had lower hematocrit than birds in the control and other CORT implant groups. Beeswax CORT implants are a low cost method of elevating plasma CORT for a prolonged time. Furthermore, because there is no need to remove these implants at the end of a study, this method may be amenable to studies of free-ranging animals.

6-Month Follow-Up of a Novel Biodegradable Drug-Eluting Stent Composed of Poly-L-Lactic Acid and Amorphous Calcium Phosphate Nanoparticles in Porcine Coronary Artery

RATIONALE

We reported previously, in porcine coronary arteries, that the novel biodegradable PowerStent Absorb paclitaxel-eluting stent had improved and sustained structural strength and functional performance at one month post-implantation.

OBJECTIVE

To report the stent performance at 6-month follow-up.

METHODS AND RESULTS

Six PowerStent Absorb and six TAXUS stents were randomly implanted in the left anterior descending and right coronary arteries of six Tibet miniature pigs. Quantitative coronary angiography (QCA) and intravascular ultrasound (IVUS) images were obtained at the time of implantation (T0) and at 6 months (T6). Two animals were sacrificed at T6 for histopathological evaluation. At T6, QCA showed that the mean luminal vascular diameter (mLD) between the PowerStent and the TAXUS stents were similar (2.36 ± 0.38 vs. 2.61 ± 0.31, respectively). Based on the IVUS analysis, the mLD and the mean lumen cross-sectional area (mCSA) in the PowerStent-treated arteries were similar between T0 and T6 (mLD: 2.74 ± 0.13 vs. 2.70 ± 0.20 and mCSA: 6.81 ± 0.62 mm2 vs. 6.68 ± 0.94 mm2). Histopathology showed that the PowerStent stents were well apposed to the vessel wall with no recoil, strut fracture and thrombus formation. The stents were fully covered with a layer of endothelial cells.

CONCLUSIONS

At six-month post-implantation, the PowerStent Absorb stents maintained their structural strength and functional performance. The development of restenosis was controlled, no stent thrombosis was observed and the stents were fully re-endothelialized. These results suggest the PowerStent Absorb stent is safe and effective for up to 6 months when implanted in porcine coronary arteries.

Degree of bioresorbable vascular scaffold expansion modulates loss of essential function

Drug-eluting bioresorbable vascular scaffolds (BVSs) have the potential to restore lumen patency, enable recovery of the native vascular environment, and circumvent late complications associated with permanent endovascular devices. To ensure therapeutic effects persist for sufficient times prior to scaffold resorption and resultant functional loss, many factors dictating BVS performance must be identified, characterized and optimized. While some factors relate to BVS design and manufacturing, others depend on device deployment and intrinsic vascular properties. Importantly, these factors interact and cannot be considered in isolation. The objective of this study is to quantify the extent to which degree of radial expansion modulates BVS performance, specifically in the context of modifying device erosion kinetics and evolution of structural mechanics and local drug elution. We systematically varied degree of radial expansion in model BVS constructs composed of poly dl-lactide-glycolide and generated in vitro metrics of device microstructure, degradation, erosion, mechanics and drug release. Experimental data permitted development of computational models that predicted transient concentrations of scaffold-derived soluble species and drug in the arterial wall, thus enabling speculation on the short- and long-term effects of differential expansion. We demonstrate that degree of expansion significantly affects scaffold properties critical to functionality, underscoring its relevance in BVS design and optimization.

STATEMENT OF SIGNIFICANCE

Bioresorbable vascular scaffold (BVS) therapy is beginning to transform the treatment of obstructive artery disease, owing to effective treatment of short term vessel closure while avoiding long term consequences such as in situ, late stent thrombosis - a fatal event associated with permanent implants such as drug-eluting stents. As device scaffolding and drug elution are temporary for BVS, the notion of using this therapy in lieu of existing, clinically approved devices seems attractive. However, there is still a limited understanding regarding the optimal lifetime and performance characteristics of erodible endovascular implants. Several engineering criteria must be met and clinical endpoints confirmed to ensure these devices are both safe and effective. In this manuscript, we sought to establish general principles for the design and deployment of erodible, drug-eluting endovascular scaffolds, with focus on how differential expansion can modulate device performance.

Sustained intravitreal delivery of dexamethasone using an injectable and biodegradable thermogel

Delivery of therapeutic agents to posterior segment of the eyes is challenging due to the anatomy and physiology of ocular barriers and thus long-acting implantable formulations are much desired. In this study, a thermogelling system composed of two poly(lactic acid-co-glycolic acid)-poly(ethylene glycol)-poly(lactic acid-co-glycolic acid) (PLGA-PEG-PLGA) triblock copolymers was developed as an injectable matrix for intravitreal drug delivery. The thermogel was prepared by mixing a sol and a precipitate of PLGA-PEG-PLGA triblock copolymers with different block ratios, among which a hydrophobic glucocorticoid, dexamethasone (DEX), was incorporated. The DEX-loaded thermogel was a low-viscous liquid at low temperature and formed a non-flowing gel at body temperature. The in vitro release rate of DEX from the thermogel could be conveniently modulated by varying the mixing ratio of the two copolymers. The long-lasting intraocular residence of the thermogel was demonstrated by intravitreal injection of a fluorescence-labeled thermogel to rabbits. Compared with a DEX suspension, the intravitreal retention time of DEX increased from a dozen hours to over 1week when being loaded in the thermogel. Additionally, intravitreal administration of the thermogel did not impair the morphology of retina and cornea. This study reveals that the injectable PLGA-PEG-PLGA thermogel is a biocompatible carrier for sustained delivery of bioactive agents into the eyes, and provides an alternative approach for treatment of posterior segment diseases.

Research Advances in Tissue Engineering Materials for Sustained Release of Growth Factors

Growth factors are a class of cytokines that stimulate cell growth and are widely used in clinical practice, such as wound healing, revascularization, bone repair, and nervous system disease. However, free growth factors have a short half-life and are instable in vivo. Therefore, the search of excellent carriers to enhance sustained release of growth factors in vivo has become an area of intense research interest. The development of controlled-release systems that protect the recombinant growth factors from enzymatic degradation and provide sustained delivery at the injury site during healing should enhance the growth factor's application in tissue regeneration. Thus, this study reviews current research on commonly used carriers for sustained release of growth factors and their sustained release effects for preservation of their bioactivity and their accomplishment in tissue engineering approaches.

Local delivery of vascular endothelial growth factor via nanofiber matrix improves liver regeneration after extensive hepatectomy in rats

Vascular endothelial growth factor (VEGF) is a potent regulator for liver regeneration following partial hepatectomy. However, intravenous delivery of VEGF has yielded limited success in promoting the regeneration of remnant liver. Here we report a new approach to locally deliver recombinant VEGF from an electrospun poly-ε-caprolactone nanofiber mesh and its effect on improving rat liver regeneration after 70% hepatectomy. After applying the VEGF-releasing nanofiber mesh to the remnant liver lobes following hepatectomy in rats, the fractions of proliferating hepatocytes increased markedly at 48 h and 72 h in comparison with the control group receiving nanofiber meshes without VEGF. The expression of endogenous VEGF in liver tissue was also higher in the VEGF-nanofiber group than those in the control group. These results demonstrate that biodegradable nanofiber meshes offer a convenient and effective approach for local and sustained delivery of VEGF to the remnant liver following partial hepatectomy.

Mechanistic analysis of PLGA/HPMC-based in-situ forming implants for periodontitis treatment

In-situ forming implant formulations based on poly(lactic-co-glycolic acid) (PLGA), acetyltributyl citrate (ATBC), minocycline HCl, N-methyl pyrrolidone (NMP) and optionally hydroxypropyl methylcellulose (HPMC) were prepared and thoroughly characterized in vitro. This includes electron paramagnetic resonance (EPR), nuclear magnetic resonance ((1)H NMR), mass change and drug release measurements under different conditions, optical microscopy, size exclusion chromatography (SEC) as well as antibacterial activity tests using gingival crevicular fluid samples from periodontal pockets of periodontitis patients. Based on these results, deeper insight into the physico-chemical phenomena involved in implant formation and the control of drug release could be gained. For instance, the effects of adding HPMC to the formulations, resulting in improved implant adherence and reduced swelling, could be explained. Importantly, the in-situ formed implants effectively hindered the growth of bacteria present in the patients' periodontal pockets. Interestingly, the systems were more effectively hindering the growth of pathogenic bacterial strains (e.g., Fusobacterium nucleatum) than that of strains with a lower pathogenic potential (e.g., Streptococcus salivarius). In vivo, such a preferential action against the pathogenic bacteria can be expected to give a chance to the healthy flora to re-colonize the periodontal pockets.

Preparation of Polymeric Prodrug Paclitaxel-Poly(lactic acid)-b-Polyisobutylene and Its Application in Coatings of a Drug Eluting Stent

To develop a novel biodegradable and quite adhesive coating material for fabricating a paclitaxel (PTX)-containing eluting stent, herein, we report two kinds of drug eluting stent (DES) materials. One of them is a prodrug, PTX end-capped poly(lactic acid)-b-polyisobutylene (PTX-PLA-b-PIB) diblock copolymer, which possesses favorable biodegradability and biocompatibility. The other is a mixture of PIB-b-PLA diblock copolymer and PTX. PIB-b-PLA was synthesized via the ring-opening polymerization (ROP) using hydroxyl-terminated polyisobutylene (PIB-OH) as the initiator, while the PTX-PLA-b-PIB prodrug was prepared through a combination of ROP and Cu(I)-catalyzed azide-alkyne cycloaddition "click" reaction. The chemical structures and compositions as well as the molecular weights and molecular weight distributions of these copolymers have been fully characterized by (1)H nuclear magnetic resonance, Fourier transform infrared, and gel permeation chromatography measurements. The thermal degradation behavior and glass transition temperature (Tg) of the copolymers were studied by thermogravimetric analysis and differential scanning calorimetry, respectively. The solutions of PTX-PLA-b-PIB and the PIB-b-PLA/PTX mixture were separately coated onto the bare metal stents to form the PTX-containing DES. Subsequently, the surface structures and morphologies of the bare stent and DES were studied by atomic force microscopy and scanning electron microscopy, respectively. The in vitro release of PTX from these stents was conducted in a buffer medium (PBS 7.4) at 37 °C. The results showed that the coating formed by a blend of PTX-PLA-b-PIB, PIB-b-PLA, and PTX yielded a release that was better sustained than those of the individual PTX-PLA-b-PIB prodrug or PIB-b-PLA/PTX mixture. MTT assays demonstrated that the stent coated with PTX-PLA-b-PIB displayed a cytotoxicity lower than that of the PIB-b-PLA/PTX mixed layer, and the biocompatibility of coatings can be effectively improved by the prodrug.

Mesoporous silica-layered biopolymer hybrid nanofibrous scaffold: a novel nanobiomatrix platform for therapeutics delivery and bone regeneration

Nanoscale scaffolds that characterize high bioactivity and the ability to deliver biomolecules provide a 3D microenvironment that controls and stimulates desired cellular responses and subsequent tissue reaction. Herein novel nanofibrous hybrid scaffolds of polycaprolactone shelled with mesoporous silica (PCL@MS) were developed. In this hybrid system, the silica shell provides an active biointerface, while the 3D nanoscale fibrous structure provides cell-stimulating matrix cues suitable for bone regeneration. The electrospun PCL nanofibers were coated with MS at controlled thicknesses via a sol-gel approach. The MS shell improved surface wettability and ionic reactions, involving substantial formation of bone-like mineral apatite in body-simulated medium. The MS-layered hybrid nanofibers showed a significant improvement in mechanical properties, in terms of both tensile strength and elastic modulus, as well as in nanomechanical surface behavior, which is favorable for hard tissue repair. Attachment, growth, and proliferation of rat mesenchymal stem cells were significantly improved on the hybrid scaffolds, and their osteogenic differentiation and subsequent mineralization were highly up-regulated by the hybrid scaffolds. Furthermore, the mesoporous surface of the hybrid scaffolds enabled the loading of a series of bioactive molecules, including small drugs and proteins at high levels. The release of these molecules was sustainable over a long-term period, indicating the capability of the hybrid scaffolds to deliver therapeutic molecules. Taken together, the multifunctional hybrid nanofibrous scaffolds are considered to be promising therapeutic platforms for stimulating stem cells and for the repair and regeneration of bone.

Chlorhexidine-loaded hydroxyapatite microspheres as an antimicrobial delivery system and its effect on in vivo osteo-conductive properties

Hydroxyapatite (HA) has been investigated as a delivery system for antimicrobial and antibacterial agents to simultaneously stimulate bone regeneration and prevent infection. Despite evidence supporting the bactericidal efficiency of these HA carriers, few studies have focused on the effect of this association on bone regeneration. In this work, we evaluated the physico-chemical properties of hydroxyapatite microspheres loaded with chlorhexidine (CHX) at two different concentrations, 0.9 and 9.1 μgCHX/cm2 HA, and characterized their effects on in vitro osteoblast viability and bone regeneration. Ultraviolet-visible spectroscopy, scanning and transmission electron microscopy associated with energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy were used to characterize the association of CHX and HA nanoparticles. The high CHX loading dose induced formation of organic CHX plate-like aggregates on the HA surface, whereas a Langmuir film was formed at the low CHX surface concentration. Quantitative evaluation of murine osteoblast viability parameters, including adhesion, mitochondrial activity and membrane integrity of cells exposed to HA/CHX extracts, revealed a cytotoxic effect for both loading concentrations. Histomorphological analysis upon implantation into the dorsal connective tissues and calvaria of rats for 7 and 42 days showed that the high CHX concentration induced the infiltration of inflammatory cells, resulting in retarded bone growth. Despite a strong decrease in in vitro cell viability, the low CHX loading dose did not impair the biocompatibility and osteoconductivity of HA during bone repair. These results indicate that high antimicrobial doses may activate a strong local inflammatory response and disrupt the long-term osteoconductive properties of CHX-HA delivery systems.

Reversible thermosensitive biodegradable polymeric actuators based on confined crystallization

We discovered a new and unexpected effect of reversible actuation of ultrathin semicrystalline polymer films. The principle was demonstrated on the example of thin polycaprolactone-gelatin bilayer films. These films are unfolded at room temperature, fold at temperature above polycaprolactone melting point, and unfold again at room temperature. The actuation is based on reversible switching of the structure of the hydrophobic polymer (polycaprolactone) upon melting and crystallization. We hypothesize that the origin of this unexpected behavior is the orientation of polycaprolactone chains parallel to the surface of the film, which is retained even after melting and crystallization of the polymer or the "crystallization memory effect". In this way, the crystallization generates a directed force, which causes bending of the film. We used this effect for the design of new generation of fully biodegradable thermoresponsive polymeric actuators, which are highly desirable for bionano-technological applications such as reversible encapsulation of cells and design of swimmers.

Nanoparticle-based brachytherapy spacers for delivery of localized combined chemoradiation therapy

PURPOSE

In radiation therapy (RT), brachytherapy-inert source spacers are commonly used in clinical practice to achieve high spatial accuracy. These implanted devices are critical technical components of precise radiation delivery but provide no direct therapeutic benefits.

METHODS AND MATERIALS

Here we have fabricated implantable nanoplatforms or chemoradiation therapy (INCeRT) spacers loaded with silica nanoparticles (SNPs) conjugated containing a drug, to act as a slow-release drug depot for simultaneous localized chemoradiation therapy. The spacers are made of poly(lactic-co-glycolic) acid (PLGA) as matrix and are physically identical in size to the commercially available brachytherapy spacers (5 mm × 0.8 mm). The silica nanoparticles, 250 nm in diameter, were conjugated with near infrared fluorophore Cy7.5 as a model drug, and the INCeRT spacers were characterized in terms of size, morphology, and composition using different instrumentation techniques. The spacers were further doped with an anticancer drug, docetaxel. We evaluated the in vivo stability, biocompatibility, and biodegradation of these spacers in live mouse tissues.

RESULTS

The electron microscopy studies showed that nanoparticles were distributed throughout the spacers. These INCeRT spacers remained stable and can be tracked by the use of optical fluorescence. In vivo optical imaging studies showed a slow diffusion of nanoparticles from the spacer to the adjacent tissue in contrast to the control Cy7.5-PLGA spacer, which showed rapid disintegration in a few days with a burst release of Cy7.5. The docetaxel spacers showed suppression of tumor growth in contrast to control mice over 16 days.

CONCLUSIONS

The imaging with the Cy7.5 spacer and therapeutic efficacy with docetaxel spacers supports the hypothesis that INCeRT spacers can be used for delivering the drugs in a slow, sustained manner in conjunction with brachytherapy, in contrast to the rapid clearance of the drugs when administered systemically. The results demonstrate that these spacers with tailored release profiles have potential in improving the combined therapeutic efficacy of chemoradiation therapy.

Three-dimensionally plotted MBG/PHBHHx composite scaffold for antitubercular drug delivery and tissue regeneration

A suitable drug-loaded scaffold that can postoperatively release an antituberculosis drug efficiently in a lesion area and help repair a bone defect is very important in the clinical treatment of bone tuberculosis (TB). In this study, a composite drug-loaded cylindrical scaffold was prepared by using three-dimensional printing technology in combination with the mesoporous confinement range, surface chemical groups, and gradual degradation of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). This achieves the slow release of a drug for as long as possible. We implanted the drug-loaded compound scaffold into New Zealand rabbits' femur defect model to study the in vivo drug release performance and osteogenic ability. The in vivo release of isoniazid and rifampicin from the prepared composites could be effectively sustained for 12 weeks in local tissues, whereas these drugs were sustained for just 2 weeks in a control group. The blood drug concentrations were very low and most concentrations were below 5 μg/ml. Therefore, the systemic toxic adverse effect is very low. In addition, the composite exhibits good osteogenic potential in a rabbit bone defect model. The results of this study indicate that this composite has great potential for treating osteoarticular TB.

Enzymatic 'stripping' and degradation of PEGylated carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) coated or functionalized with PEG chains of different molecular weight were assessed for their propensity to undergo biodegradation under in vitro conditions using recombinant myeloperoxidase (MPO) or ex vivo using freshly isolated primary human neutrophils. Our findings suggest that under natural conditions, a combined process of 'stripping' (i.e., defunctionalization) and biodegradation of PEG-SWCNTs might occur and that PEG-SWCNTs are a promising--and degradable--nanomedicine vector.

VEGF-releasing suture material for enhancement of vascularization: development, in vitro and in vivo study

As it has been demonstrated that bioactive substances can be delivered locally using coated surgical suture materials, the authors developed a vascular endothelial growth factor (VEGF)-releasing suture material that should promote vascularization and potentially wound healing. In this context, the study focused on the characterization of the developed suture material and the verification of its biological activity, as well as establishing a coating process that allows reproducible and stable coating of a commercially available polydioxanone suture material with poly(l-lactide) (PLLA) and 0.1μg and 1.0μg VEGF. The in vitro VEGF release kinetics was studied using a Sandwich ELISA. The biological activity of the released VEGF was investigated in vitro using human umbilical vein endothelial cells. The potential of the VEGF-releasing suture material was also studied in vivo 5days after implantation in the hind limb of Wistar rats, when the histological findings were analyzed. The essential results, enhanced cell viability in vitro as well as significantly increased vascularization in vivo, were achieved using PLLA/1.0μg VEGF-coated suture material. Furthermore, ELISA measurements revealed a high reproducibility of the VEGF release behavior. Based on the results achieved regarding the dose-effect relationship of VEGF, the stability during its processing and the release behavior, it can be predicted that a bioactive suture material would be successful in later in vivo studies. Therefore, this knowledge could be the basis for future studies, where bioactive substances with different modes of action are combined for targeted, overall enhancement of wound healing.

[Correlations between micromeritic properties of mixing powders of danshen extract and formability of their pellets]

It was difficult to prepare traditional Chinese medicine pellets due to the adverse characteristics of the herbal extract. In this study, Danshen extract (DS) powder mixed with different proportions of microcrystalline cellulose (MCC), lactose and starch were made into pellets by extrusion-spheronization. Particle size, span, bulk density, tapping density, compressibility, Hausner ratio and angle of repose were used to evaluate the micromeritic properties of mixing powders. Feret diameter, aspect ratio, yield, density and friability were used to evaluate the properties of the pellets. The correlations between micromeritic properties of raw material powders and the formability of their pellets were analyzed by cluster analysis, principal component analysis and partial least squares regression analysis. As a result, the particle size of the powders was negatively correlated with the size, density, yield, and was positively correlated with the friability of their pellets. The span, density, compressibility and angle of repose of the powders were positively correlated with the size, density, yield, and were negatively correlated with the friability of their pellets. So there were certain correlations between the micromeritic properties of raw material powders and the properties of their pellets prepared by extrusion-spheronization. This research provided a foundation for the technology and method of traditional Chinese medicine extract pellets.

In vitro and in vivo evaluation of silicated hydroxyapatite and impact of insulin adsorption

This study evaluates the biological behaviour, in vitro and in vivo, of silicated hydroxyapatite with and without insulin adsorbed on the material surface. Insulin was successfully adsorbed on hydroxyapatite and silicated hydroxyapatite bioceramics. The modification of the protein secondary structure after the adsorption was investigated by means of infrared and circular dichroism spectroscopic methods. Both results were in agreement and indicated that the adsorption process was likely to change the secondary structure of the insulin from a majority of α-helix to a β-sheet form. The biocompatibility of both materials, with and without adsorbed insulin on their surface, was demonstrated in vitro by indirect and direct assays. A good viability of the cells was found and no proliferation effect was observed regardless of the material composition and of the presence or absence of insulin. Dense granules of each material were implanted subcutaneously in mice for 1, 3 and 9 weeks. At 9 weeks of implantation, a higher inflammatory response was observed for silicated hydroxyapatite than for pure hydroxyapatite but no significant effect of adsorbed insulin was detected. Though the presence of silicon in hydroxyapatite did not improve the biological behaviour, the silicon substituted hydroxyapatite remained highly viable.

Novel sustained-release of propafenone through pellets: preparation and in vitro/in vivo evaluation

In this study, an extrusion-spheronization method was applied successfully to fabricate propafenone hydrochloride (PPF) sustained-release pellets. Using scanning electron microscopy, it was shown that the PPF pellets had a mean size of approximately 950 µm with a spherical shape. The in vitro release profiles indicated that the release of PPF from the pellets exhibited a sustained release behavior. The relatively high correlation coefficient (r) values obtained from the analysis of the amount of the drug released versus the square root of time indicated that the release followed a zero order kinetic model. A similar phenomenon was also observed in a pharmacokinetic study in dogs, in which the area under the curve (AUC) of the pellet formulation was 1.2-fold higher than that of PPF tablets. The present work demonstrated the feasibility of controlled delivery of PPF utilizing microcrystalline cellulose (MCC)-based pellets.

Bone regeneration induced by an in situ gel-forming poloxamine, bone morphogenetic protein-2 system

The aim of this study was to confirm previously shown, in vitro osteogenic induction by the Tetronics T908 and T1307 in a critical-size, rat calvaria defect. In vivo, the osteogenic activity of the hydrogels was comparable to in vitro, but less pronounced. However, similar to in vitro, the system was strongly potentiated by incorporating 6.5 microg of bone morphogenetic protein-2 in solution or pre-encapsulated in poly(lactic-co-glycolic) acid microspheres. These two systems extended the in vivo release of bone morphogenetic protein-2, determined with 125I- bone morphogenetic protein-2, for one and two additional weeks, respectively, time enough to fill approximately 40% and 90% of the defect with well-organized bone. Furthermore, the structural characteristics of Tetronic hydrogels together with their biocompatibility, injectability, and adaptability to multiple defect sizes and shapes suggest their role as new, potential bone morphogenetic protein-2 delivery, low-cost scaffolds for minor as well as critical bone defects.

Optimizing the concentration of quaternary ammonium dimethacrylate monomer in bis-GMA/TEGDMA dental resin system for antibacterial activity and mechanical properties

Four novel quaternary ammonium dimethacrylate monomers named IMQ (side alkyl chain length from 12 to 18) were synthesized with the aim to synthesize dental resin with antibacterial activity. All of IMQs were added into bis-GMA/TEGDMA dental resin system with a series of mass ratio (5, 10, and 20 wt%), double bond conversion (DC), flexural strength (FS), modulus of elasticity (FM) and biofilm formation inhibitory effect were studied. According to the results of DC, FS, FM, and the biofilm inhibitory effect, IMQ-16 containing polymer had the best comprehensive properties, and the optimal concentration of IMQ-16 in bis-GMA/TEGDMA dental resin would be in the range of 5-10 wt%.

Release of Cu2+ from a copper-filled TiO2 coating in a rabbit model for total knee arthroplasty

The aim of this study was the investigation of a copper-filled TiO2 coating, that in vitro showed good antibacterial properties combined with good tissue tolerance in an animal model. To better understand the antibacterial mechanism of the bioactive coating the release of copper (Cu) ions over time was monitored to be able to detect possible threats as well as possible fields of application. 30 New Zealand White rabbits were divided into two groups with 15 animals per group. In group 1 (control group) Ti6Al4 V bolts were implanted into the distal femur, in group 2 the Ti6Al4 V bolts were coated with four TiO2-coatings with integrated Cu(2+)-ions (4 × Cu-TiO2). Blood tests were performed weekly until the animals were sacrificed 4 weeks postoperative. The maximum peak of Cu and ceruloplasmin concentration could be seen in both groups one week postoperative, whereas the Cu values in group II were significantly higher. The Cu concentration in both groups approximated the initial basic values 4 weeks postoperative. The 4 × Cu-TiO2 coating tested in our rabbit model for total knee arthroplasty is an active coating that releases potentially antibacterial Cu(2+) for 4 weeks with a peak 1 week postoperative. The bioactive coating could be a promising approach for a use in the field of implant related infection, orthopaedic revision and tumor surgery in the future.

Alterations in the endometrium of rats, rabbits, and Macaca mulatta that received an implantation of copper/low-density polyethylene nanocomposite

A copper/low-density polyethylene nanocomposite (nano-Cu/LDPE), a potential intrauterine device component material, has been developed from our research. A logical extension of our previous work, this study was conducted to investigate the expression of plasminogen activator inhibitor 1 (PAI-1), substance P (SP), and substance P receptor (SP-R) in the endometrium of Sprague Dawley rats, New Zealand White rabbits, and Macaca mulatta implanted with nano-Cu/LDPE composite. The influence of the nano-Cu/LDPE composite on the morphology of the endometrium was also investigated. Animals were randomly divided into five groups: the sham-operated control group (SO group), bulk copper group (Cu group), LDPE group, and nano-Cu/LDPE groups I and II. An expression of PAI-1, SP, and SP-R in the endometrial tissues was examined by immunohistochemistry at day 30, 60, 90, and 180 postimplantation. The significant difference for PAI-1, SP, and SP-R between the nano-Cu/LDPE groups and the SO group (P<0.05) was identified when the observation period was terminated, and the changes of nano-Cu/LDPE on these parameters were less remarkable than those of the Cu group (P<0.05). The damage to the endometrial morphology caused by the nano-Cu/LDPE composite was much less than that caused by bulk copper. The nano-Cu/LDPE composite might be a potential substitute for conventional materials for intrauterine devices in the future because of its decreased adverse effects on the endometrial microenvironment.