Delivery systems for small molecule drugs, proteins, and DNA: the neuroscience/biomaterial interface

Delayed administration of interleukin-4 coacervate alleviates the neurotoxic phenotype of astrocytes and promotes functional recovery after a contusion spinal cord injury

Objective. Macrophages and astrocytes play a crucial role in the aftermath of a traumatic spinal cord injury (SCI). Infiltrating macrophages adopt a pro-inflammatory phenotype while resident astrocytes adopt a neurotoxic phenotype at the injury site, both of which contribute to neuronal death and inhibit axonal regeneration. The cytokine interleukin-4 (IL-4) has shown significant promise in preclinical models of SCI by alleviating the macrophage-mediated inflammation and promoting functional recovery. However, its effect on neurotoxic reactive astrocytes remains to be elucidated, which we explored in this study. We also studied the beneficial effects of a sustained release of IL-4 from an injectable biomaterial compared to bolus administration of IL-4.Approach. We fabricated a heparin-based coacervate capable of anchoring and releasing bioactive IL-4 and tested its efficacyin vitroandin vivo. Main results. We show that IL-4 coacervate is biocompatible and drives a robust anti-inflammatory macrophage phenotype in culture. We also show that IL-4 and IL-4 coacervate can alleviate the reactive neurotoxic phenotype of astrocytes in culture. Finally, using a murine model of contusion SCI, we show that IL-4 and IL-4 coacervate, injected intraspinally 2 d post-injury, can reduce macrophage-mediated inflammation, and alleviate neurotoxic astrocyte phenotype, acutely and chronically, while also promoting neuroprotection with significant improvements in hindlimb locomotor recovery. We observed that IL-4 coacervate can promote a more robust regenerative macrophage phenotypein vitro, as well as match its efficacyin vivo,compared to bolus IL-4.Significance. Our work shows the promise of coacervate as a great choice for local and prolonged delivery of cytokines like IL-4. We support this by showing that the coacervate can release bioactive IL-4, which acts on macrophages and astrocytes to promote a pro-regenerative environment following a SCI leading to robust neuroprotective and functional outcomes.

Harnessing DNA origami's therapeutic potential for revolutionizing cardiovascular disease treatment: A comprehensive review

DNA origami is a cutting-edge nanotechnology approach that creates precise and detailed 2D and 3D nanostructures. The crucial feature of DNA origami is how it is created, which enables precise control over its size and shape. Biocompatibility, targetability, programmability, and stability are further advantages that make it a potentially beneficial technique for a variety of applications. The preclinical studies of sophisticated programmable nanomedicines and nanodevices that can precisely respond to particular disease-associated triggers and microenvironments have been made possible by recent developments in DNA origami. These stimuli, which are endogenous to the targeted disorders, include protein upregulation, pH, redox status, and small chemicals. Oncology has traditionally been the focus of the majority of past and current research on this subject. Therefore, in this comprehensive review, we delve into the intricate world of DNA origami, exploring its defining features and capabilities. This review covers the fundamental characteristics of DNA origami, targeting DNA origami to cells, cellular uptake, and subcellular localization. Throughout the review, we emphasised on elucidating the imperative for such a therapeutic platform, especially in addressing the complexities of cardiovascular disease (CVD). Moreover, we explore the vast potential inherent in DNA origami technology, envisioning its promising role in the realm of CVD treatment and beyond.

Nucleic acid therapies for CNS diseases: Pathophysiology, targets, barriers, and delivery strategies

Nucleic acid therapeutics have emerged as one of the very advanced and efficacious treatment approaches for debilitating health conditions, including those diseases affecting the central nervous system (CNS). Precise targeting with an optimal control over gene regulation confers long-lasting benefits through the administration of nucleic acid payloads via viral, non-viral, and engineered vectors. The current review majorly focuses on the development and clinical translational potential of non-viral vectors for treating CNS diseases with a focus on their specific design and targeting approaches. These carriers must be able to surmount the various intracellular and extracellular barriers, to ensure successful neuronal transfection and ultimately attain higher therapeutic efficacies. Additionally, the specific challenges associated with CNS administration also include the presence of blood-brain barrier (BBB), the complex pathophysiological and biochemical changes associated with different disease conditions and the existence of non-dividing cells. The advantages offered by lipid-based or polymeric systems, engineered proteins, particle-based systems coupled with various approaches of neuronal targeting have been discussed in the context of a variety of CNS diseases. The possibilities of rapid yet highly efficient gene modifications rendered by the breakthrough methodologies for gene editing and gene manipulation have also opened vast avenues of research in neuroscience and CNS disease therapy. The current review also underscores the extensive scientific efforts to optimize specialized, efficacious yet non-invasive and safer administration approaches to overcome the therapeutic delivery challenges specifically posed by the CNS transport barriers and the overall obstacles to clinical translation.

Emerging uses of PLA-PEG copolymer in cancer drug delivery

Traditional therapies need high systematic dosages that not only destroys cancerous cells but also healthy cells. To overcome this problem recent advancement in nanotechnology specifically in nanomaterials has been extensively done for various biological applications, such as targeted drug delivery. Nanotechnology, as a frontier science, has the potential to break down all the obstacles to be more effective and secure drug delivery system. It is possible to develop nanopolymer based drug carrier that can target drugs with extreme accuracy. Polymers can advance drug delivery technologies by allowing controlled release of therapeutic drugs in stable amounts over long duration of time. For controlled drug delivery, biodegradable synthetic polymers have various benefits over non-biodegradable polymers. Biodegradable polymer either are less toxic or non-toxic. Polylactic Acid (PLA) is one of the most remarkable amphipathic polymers which make it one of the most suitable materials for polymeric micelles. Amphiphilic nanomaterial, such as Polyethylene Glycol (PEG), is one of the most promising carrier for tumor targeting. PLA-PEG as a copolymer has been generally utilized as drug delivery system for the various types of cancer. Chemotherapeutic drugs are stacked into PLA-PEG copolymer and as a result their duration time delays, hence medications arrive at specific tumor site.

The biological applications of DNA nanomaterials: current challenges and future directions

DNA, a genetic material, has been employed in different scientific directions for various biological applications as driven by DNA nanotechnology in the past decades, including tissue regeneration, disease prevention, inflammation inhibition, bioimaging, biosensing, diagnosis, antitumor drug delivery, and therapeutics. With the rapid progress in DNA nanotechnology, multitudinous DNA nanomaterials have been designed with different shape and size based on the classic Watson-Crick base-pairing for molecular self-assembly. Some DNA materials could functionally change cell biological behaviors, such as cell migration, cell proliferation, cell differentiation, autophagy, and anti-inflammatory effects. Some single-stranded DNAs (ssDNAs) or RNAs with secondary structures via self-pairing, named aptamer, possess the ability of targeting, which are selected by systematic evolution of ligands by exponential enrichment (SELEX) and applied for tumor targeted diagnosis and treatment. Some DNA nanomaterials with three-dimensional (3D) nanostructures and stable structures are investigated as drug carrier systems to delivery multiple antitumor medicine or gene therapeutic agents. While the functional DNA nanostructures have promoted the development of the DNA nanotechnology with innovative designs and preparation strategies, and also proved with great potential in the biological and medical use, there is still a long way to go for the eventual application of DNA materials in real life. Here in this review, we conducted a comprehensive survey of the structural development history of various DNA nanomaterials, introduced the principles of different DNA nanomaterials, summarized their biological applications in different fields, and discussed the current challenges and further directions that could help to achieve their applications in the future.

Octadecyltrichlorosilane Incorporated Alginate Micro-granules as Sustained-Release Carriers for Small Hydrophilic Molecules

Background:

Hydrogels are excellent drug carriers, but their inability to retain hydrophilic drugs for a prolonged period of time has greatly limited their usage. Research has mostly focused on intricate designs and manipulations of hydrogels to expand their applications in drug delivery.

Objective:

In this study, a simple approach by incorporating a hydrophobic agent, octadecyltrichlorosilane (OTS), to alginate hydrogel micro-granules (Alg-Ms), was investigated as an effective technique to prolong the release of small hydrophilic drugs.

Methods:

Sodium Benzoate (SB), a highly water-soluble antimicrobial and anti-inflammatory compound, was used as a model drug. The presence of hydrophobic OTS impeded swelling of these OTS incorporated Alg-Ms (OTS-Alg-Ms), hence sustaining the release of SB.

Results:

The release data was fitted with Ritger-Peppas and Peppas-Sahlin models and the results showed that SB released from OTS-Alg-Ms with higher OTS content was mainly controlled by Fickian diffusion; with a lower OTS content, OTS-Alg-Ms swelled more easily, the combined diffusion and swelling led to a faster SB release.

Conclusion:

Thus, by simply tuning the OTS concentration in the solution where Alg-Ms were briefly submerged in a predefined release period, from hours to a few days, small hydrophilic drugs from these OTS-Alg-Ms could be successfully achieved.

Influencing neuroplasticity in stroke treatment with advanced biomaterials-based approaches

Since the early 1990s, we have known that the adult brain is not static and has the capacity to repair itself. The delivery of various therapeutic factors and cells have resulted in some exciting pre-clinical and clinical outcomes in stroke models by targeting post-injury plasticity to enhance recovery. Developing a deeper understanding of the pathways that modulate plasticity will enable us to optimize delivery strategies for therapeutics and achieve more robust effects. Biomaterials are a key tool for the optimization of these potential treatments, owing to their biocompatibility and tunability. In this review, we identify factors and targets that impact plastic processes known to contribute to recovery, discuss the role of biomaterials in enhancing the efficacy of treatment strategies, and suggest combinatorial approaches based on the stage of injury progression.

Heparin-based hydrogels with tunable sulfation & degradation for anti-inflammatory small molecule delivery

Sustained release of anti-inflammatory agents remains challenging for small molecule drugs due to their low molecular weight and hydrophobicity. Therefore, the goal of this study was to control the release of a small molecule anti-inflammatory agent, crystal violet (CV), from hydrogels fabricated with heparin, a highly sulfated glycosaminoglycan capable of binding positively-charged molecules such as CV. In this system, both electrostatic interactions between heparin and CV and hydrogel degradation were tuned simultaneously by varying the level of heparin sulfation and varying the amount of dithiothreitol within hydrogels, respectively. It was found that heparin sulfation significantly affected CV release, whereby more sulfated heparin hydrogels (Hep and Hep(-N)) released CV with near zero-order release kinetics (R-squared values between 0.96-0.99). Furthermore, CV was released more quickly from fast-degrading hydrogels than slow-degrading hydrogels, providing a method to tune total CV release between 5-15 days while maintaining linear release kinetics. In particular, N-desulfated heparin hydrogels exhibited efficient CV loading (∼90% of originally included CV), near zero-order CV release kinetics, and maintenance of CV bioactivity after release, making this hydrogel formulation a promising CV delivery vehicle for a wide range of inflammatory diseases.

Multidisciplinary Perspectives for Alzheimer's and Parkinson's Diseases: Hydrogels for Protein Delivery and Cell-Based Drug Delivery as Therapeutic Strategies

This review presents two intriguing multidisciplinary strategies that might make the difference in the treatment of neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. The first proposed strategy is based on the controlled delivery of recombinant proteins known to play a key role in these neurodegenerative disorders that are released in situ by optimized polymer-based systems. The second strategy is the use of engineered cells, encapsulated and delivered in situ by suitable polymer-based systems, that act as drug reservoirs and allow the delivery of selected molecules to be used in the treatment of Alzheimer's and Parkinson's diseases. In both these scenarios, the design and development of optimized polymer-based drug delivery and cell housing systems for central nervous system applications represent a key requirement. Materials science provides suitable hydrogel-based tools to be optimized together with suitably designed recombinant proteins or drug delivering-cells that, once in situ, can provide an effective treatment for these neurodegenerative disorders. In this scenario, only interdisciplinary research that fully integrates biology, biochemistry, medicine and materials science can provide a springboard for the development of suitable therapeutic tools, not only for the treatment of Alzheimer's and Parkinson's diseases but also, prospectively, for a wide range of severe neurodegenerative disorders.

Evaluation of a photocrosslinkable hydroxyethyl chitosan hydrogel as a potential drug release system for glaucoma surgery

Hydroxyethyl chitosan (HECTS) is a critical derivative of chitosan that has been widely used as biomedical materials due to great water-solubility and excellent biocompatibility. Here, photosensitive hydroxyethyl chitosan was synthesized by introducing azide group on NH2 of HECTS (HECTS-AZ), afterwards FTIR and ¹H NMR spectra were detected to confirm the formation of HECTS-AZ. The solution of HECTS-AZ can achieve a sol-gel transition through UV irradiation for 30 s. The evaluation of biocompability and biodegradability in vivo was conducted in rats, visual and pathological examinations exhibited the HECTS-AZ has excellent biocompability and degradation time of the hydrogel is more than 14 weeks. Furthermore, HECTS-AZ hydrogel as an ocular drug delivery system loading heparin was prepared to implant under sclera of rabbit after glaucoma filtration surgery (GFS). The experimental results demonstrated the heparin loaded hydrogel can effectively maintain filtration bleb and lowing intraocular pressure (IOP) after GFS for prolonged time. Besides, obvious inflammatory reactions and side effects have not been observed in ocular during the experimental period. In conclusion, the HECTS-AZ hydrogel is a potential drug delivery device for the treatment of glaucoma and other ocular diseases.

Efficient Dual siRNA and Drug Delivery Using Engineered Lipoproteoplexes

An engineered supercharged coiled-coil protein (CSP) and the cationic transfection reagent Lipofectamine 2000 are combined to form a lipoproteoplex for the purpose of dual delivery of siRNA and doxorubicin. CSP, bearing an external positive charge and axial hydrophobic pore, demonstrates the ability to condense siRNA and encapsulate the small-molecule chemotherapeutic, doxorubicin. The lipoproteoplex demonstrates improved doxorubicin loading relative to Lipofectamine 2000. Furthermore, it induces effective transfection of GAPDH (60% knockdown) in MCF-7 breast cancer cells with efficiencies comparing favorably to Lipofectamine 2000. When the lipoproteoplex is loaded with doxorubicin, the improved doxorubicin loading (∼40 μg Dox/mg CSP) results in a substantial decrease in MCF-7 cell viability.

Reducing neuroinflammation by delivery of IL-10 encoding lentivirus from multiple-channel bridges

The spinal cord is unable to regenerate after injury largely due to growth‐inhibition by an inflammatory response to the injury that fails to resolve, resulting in secondary damage and cell death. An approach that prevents inhibition by attenuating the inflammatory response and promoting its resolution through the transition of macrophages to anti‐inflammatory phenotypes is essential for the creation of a growth permissive microenvironment. Viral gene delivery to induce the expression of anti‐inflammatory factors provides the potential to provide localized delivery to alter the host inflammatory response. Initially, we investigated the effect of the biomaterial and viral components of the delivery system to influence the extent of cell infiltration and the phenotype of these cells. Bridge implantation reduces antigen‐presenting cell infiltration at day 7, and lentivirus addition to the bridge induces a transient increase in neutrophils in the spinal cord at day 7 and macrophages at day 14. Delivery of a lentivirus encoding IL‐10, an anti‐inflammatory factor that inhibits immune cell activation and polarizes the macrophage population towards anti‐inflammatory phenotypes, reduced neutrophil infiltration at both day 7 and day 28. Though IL‐10 lentivirus did not affect macrophages number, it skewed the macrophage population toward an anti‐inflammatory M2 phenotype and altered macrophage morphology. Additionally, IL‐10 delivery resulted in improved motor function, suggesting reduced secondary damage and increased sparing. Taken together, these results indicate that localized expression of anti‐inflammatory factors, such as IL‐10, can modulate the inflammatory response following spinal cord injury, and may be a key component of a combinatorial approach that targets the multiple barriers to regeneration and functional recovery.

Surface-Mediated Stimuli Responsive Delivery of Organic Molecules from Porous Carriers to Adhered Cells

The alternating layer-by-layer deposition of oppositely charged polyelectrolytes on fluorescence-dye-(Hst)-loaded zeolites L ((Hst) Zeo-PSS/PLL) is described. The arrays and nanocomposite (NC) hydrogels of (Hst) Zeo-PSS/PLL are prepared. The subsequent cell experiments show the potential application of arrays and NC hydrogels of (Hst) Zeo-PSS/PLL as alternative 2D- and 3D-surfaces, respectively, for 2D- and 3D-surface-mediated controlled organic molecules delivery applications.

A drug delivery hydrogel system based on activin B for Parkinson's disease

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. Activins are members of the superfamily of transforming growth factors and have many potential neuroprotective effects. Herein, at the first place, we verified activin B's neuroprotective role in a PD model, and revealed that activin B's fast release has limited function in the PD therapy. To this end, we developed a multi-functional crosslinker based thermosensitive injectable hydrogels to deliver activin B, and stereotactically injected the activin B-loaded hydrogel into the striatum of a mouse model of PD. The histological evaluation showed that activin B can be detected even 5 weeks post-surgery in PD mice implanted with activin B-loaded hydrogels, and activin B-loaded hydrogels can significantly increase the density of tyrosine hydroxylase positive (TH(+)) nerve fibers and reduce inflammatory responses. The behavioral evaluation demonstrated that activin B-loaded hydrogels significantly improved the performance of the mice in the PD model. Meanwhile, we found that hydrogels can slightly induce the activation of microglia cells and astrocytes, while cannot induce apoptosis in the striatum. Overall, our data demonstrated that the developed activin B-loaded hydrogels provide sustained release of activin B for over 5 weeks and contribute to substantial cellular protection and behavioral improvement, suggesting their potential as a therapeutic strategy for PD.

Intracellularly Biodegradable Polyelectrolyte/Silica Composite Microcapsules as Carriers for Small Molecules

Microcapsules that can be efficiently loaded with small molecules and effectively released at the target area through the degradation of the capsule shells hold great potential for treating diseases. Traditional biodegradable polyelectrolyte (PE) capsules can be degraded by cells and eliminated from the body but fail to encapsulate drugs with small molecular weight. Here, we report a poly-l-arginine hydrochloride (PARG)/dextran sulfate sodium salt (DEXS)/silica (SiO2) composite capsule that can be destructed in cells and of which the in situ formed inorganic SiO2 enables loading of small model molecules, Rhodamine B (Rh-B). The composite capsules were fabricated based on the layer-by-layer (LbL) technique and the hydrolysis of tetraethoxysilane (TEOS). Capsules composed of nondegradable PEs and SiO2, polyllamine hydrochloride (PAH)/poly(sodium 4-styrenesulfonate) (PSS)/silica (the control sample), were prepared and briefly compared with the degradable composite capsules. An intracellular degradation study of both types of composite capsules revealed that PARG/DEXS/silica capsules were degraded into fragments and lead to the release of model molecules in a relatively short time (2 h), while the structure of PAH/PSS/silica capsules remained intact even after 3 days incubation with B50 cells. Such results indicated that the polymer components played a significant role in the degradability of the SiO2. Specifically, PAH/PSS scaffolds blocked the degradation of SiO2. For PARG/DEXS/silica capsules, we proposed the effects of both hydrolytic degradation of amorphous silica and enzymatic degradation of PARG/DEXS polymers as a cell degradation mechanism. All the results demonstrated a new type of functional composite microcapsule with low permeability, good biocompatibility, and biodegradability for potential medical applications.

Harnessing nanoparticles for immune modulation

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NPs can be generated from numerous biocompatible compounds.

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Specific physiochemical characteristics can be manipulated to modulate the immune response.

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Severe inflammation can be treated using NP-based approaches.

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Antigen delivery via NPs can restore peripheral immune tolerance.

Recent approaches using nanoparticles engineered for immune regulation have yielded promising results in preclinical models of disease. The number of nanoparticle therapies is growing, fueled by innovations in nanotechnology and advances in understanding of the underlying pathogenesis of immune-mediated diseases. In particular, recent mechanistic insight into the ways in which nanoparticles interact with the mononuclear phagocyte system and impact its function during homeostasis and inflammation have highlighted the potential of nanoparticle-based therapies for controlling severe inflammation while concurrently restoring peripheral immune tolerance in autoimmune disease. Here we review recent advances in nanoparticle-based approaches aimed at immune-modulation, and discuss these in the context of concepts in polymeric nanoparticle development, including particle modification, delivery and the factors associated with successful clinical deployment.

Computational design and experimental characterization of peptides intended for pH-dependent membrane insertion and pore formation

There are many opportunities to use macromolecules, such as peptides and oligonucleotides, for intracellular applications. Despite this, general methods for delivering these molecules to the cytosol in a safe and efficient manner are not available. Efforts to develop a variety of intracellular drug delivery systems such as viral vectors, lipoplexes, nanoparticles, and amphiphilic peptides have been made, but various challenges such as delivery efficiency, toxicity, and controllability remain. A central challenge is the ability to selectively perturb, not destroy, the membrane to facilitate cargo introduction. Herein, we describe our efforts to design and characterize peptides that form pores inside membranes at acidic pH, so-called pH-switchable pore formation (PSPF) peptides, as a potential means for facilitating cargo translocation through membranes. Consistent with pore formation, these peptides exhibit low-pH-triggered selective release of ATP and miRNA, but not hemoglobin, from red blood cells. Consistent with these observations, biophysical studies (tryptophan fluorescence, circular dichroism, size-exclusion chromatography, analytical ultracentrifugation, and attenuated total reflectance Fourier transformed infrared spectroscopy) show that decreased pH destabilizes the PSPF peptides in aqueous systems while promoting their membrane insertion. Together, these results suggest that reduced pH drives insertion of PSPF peptides into membranes, leading to target-specific escape through a proposed pore formation mechanism.

Poly(lactide-co-glycolide) microspheres for MRI-monitored transcatheter delivery of sorafenib to liver tumors

The multi-kinase inhibitor (MKI) sorafenib can be an effective palliative therapy for patients with hepatocellular carcinoma (HCC). However, patient tolerance is often poor due to common systemic side effects following oral administration. Local transcatheter delivery of sorafenib to liver tumors has the potential to reduce systemic toxicities while increasing the dose delivered to targeted tumors. We developed sorafenib-eluting PLG microspheres for delivery by intra-hepatic transcatheter infusion in an orthotropic rodent HCC model. The particles also encapsulated iron-oxide nanoparticles permitting magnetic resonance imaging (MRI) of intra-hepatic biodistributions. The PLG microspheres (diameter≈1μm) were loaded with 18.6% (w/w) sorafenib and 0.54% (w/w) ferrofluid and 65.2% of the sorafenib was released within 72h of media exposure. In vitro studies demonstrated significant reductions in HCC cell proliferation with increasing doses of the sorafenib-eluting microspheres, where the estimated IC50 was a 29μg/mL dose of microspheres. During in vivo studies, MRI permitted intra-procedural visualization of intra-hepatic microsphere delivery. At 72h after microsphere infusion, microvessel density was significantly reduced in tumors treated with the sorafenib-eluting microspheres compared to both sham control tumors (by 35%) and controls (by 30%). These PLG microspheres offer the potential to increase the efficacy of molecularly targeted MKI therapies while reducing systemic exposures via selective catheter-directed delivery to HCC.

Effects of releasing recombinant human growth and differentiation factor-5 from poly(lactic-co-glycolic acid) microspheres for repair of the rat degenerated intervertebral disc

Purpose:

The objective of this study was to investigate the therapeutic potential of poly(lactic- co-glycolic acid) (PLGA) microspheres loaded with recombinant human growth and differentiation factor-5 (rhGDF-5) on the disc degeneration induced by needle puncture in a rat caudal disc model.

Methods:

The rhGDF-5-loaded PLGA microspheres were prepared by the water-oil-water double-emulsion solvent evaporation method, and release kinetics was determined over 42 days. Rats that underwent 21-G needle puncture at rat tail discs were injected with rhGDF-5/PLGA microspheres at four weeks after needle injury. At eight weeks after the injection, disc height, glycosaminoglycans content, and DNA content of the discs were evaluated. In addition, gene expression analysis of aggrecan, collagen type I, and collagen type II in the rat nucleus pulposus was measured by real-time polymerase chain reaction. Rat discs were also assessed by histology using hematoxylin and eosin stain.

Results:

Encapsulation of rhGDF-5 in PLGA microspheres guaranteed a sustained release of active rhGDF-5 for more than 42 days. The injection of GDF-5/PLGA microspheres resulted in a statistically significant restoration of disc height ( p < 0.01), improvement of sulfated glycosaminoglycan ( p < 0.05), DNA content ( p < 0.05), and significantly increased mRNA levels of collagen type II ( p < 0.01), and the differentiation index (the ratio of collagen type II to collagen type I, p < 0.01). In addition, rhGDF-5/PLGA microspheres treatment also improved histological changes induced by needle puncture.

Conclusions:

The results of this study suggest that injection of rhGDF-5 loaded in PLGA microspheres into rat tail discs may be as a promising therapy strategy to regenerate or repair the degenerative disc.

Effect of application route of the ghrelin analog BIM-28131 (RM-131) on body weight and body composition in a rat heart failure model

Chronic heart failure (CHF) remains one of the most challenging diseases in terms of numbers and disease management, particularly so, if the CHF patient develops cardiac cachexia. Ghrelin and its analogs have been suggested to improve body weight and cardiac function in heart failure models and exploratory human clinical studies. However, most ghrelin compounds are peptides and need to be injected several times per day, which affects the quality of life of patients. Here, we compared two application routes, three times daily subcutaneous (sc) injections to continuous infusion using osmotic mini-pumps in a rat model of CHF. Moreover, the effects were also compared to three times daily sc injections of growth hormone (GH). Rats were treated for 28 d. The results show that treatment with 50 or 100 nmol/kg/d BIM-28131 (RM-131) potently induces body weight gain, fat and lean mass compared to placebo. The gain of lean mass was equal to the gain of lean mass in the 2mg/kg/d GH group and superior to 250 μg/kg/d GH. Both GH and BIM-28131 increased levels of insulin-like growth factor-1 to a similar extent. Little effect was seen on cardiac function; only cardiac output was improved by either high dose BIM-28131 or GH. Overall the effects of BIM-28131 were similar in both application routes.

Controlled release behaviour of protein-loaded microparticles prepared via coaxial or emulsion electrospray

Biodegradable poly (lactic-co-glycolic acid) (PLGA) microparticles are an effective way to achieve sustained drug release. In this study, we investigated a sustained release model of PLGA microparticles with incorporated protein via either emulsion or coaxial electrospray techniques. PLGA (75:25) was used as the carrier, and bovine serum albumin as a model protein. Coaxial electrospray resulted in a type of core-shell structure with mean diameters of 2.41 ± 0.60 µm and a centralised protein distribution within the core. Emulsion electrospray formed bigger microparticles with mean diameters of 22.75 ± 8.05 µm and a heterogeneous protein distribution throughout the microparticles. The coaxial electrospray microparticles presented a much slighter burst release than the emulsion electrospray microparticles. Loading efficiency was significantly higher (p < 0.05) in the coaxial group than emulsion group. This indicated that both emulsion and coaxial electrospray could produce protein-loaded microparticles with sustained release behaviour, but the former revealed a superior approach for drug delivery.

Controlled release of imatinib mesylate from PLGA microspheres inhibit craniopharyngioma mediated angiogenesis

Poly(lactic-co-glycolic acid) microspheres loaded with imatinib mesylate has been developed as a new therapeutic strategy to prevent craniopharyngioma recurrence. Microspheres composed of different lactic/glycolic acid ratios, molecular weights and drug compositions were synthesized and loaded with imatinib mesylate by modified double-emulsion/solvent evaporation technique and subsequently characterized by particle-size distribution, scanning electron microscopy, encapsulation efficiency and in vitro drug release. Inhibitory potential of imatinib containing microspheres on tumor neovascularization was investigated on craniopharyngioma tumor samples by rat cornea angiogenesis assay. Results showed that microspheres in different LA:GA ratios [LA:GA 50:50 (G50), 75:25 (G25), 85:15 (G15)] considerably reduced neovascularization induced by recurrent tumor samples in an in vivo angiogenesis assay (P < 0.01). Our data indicate that local delivery of imatinib mesylate to the post-surgical tumoral cavity using biodegradable microspheres may be a promising biologically selective approach to prevent the recurrence of craniopharyngiomas, via inhibition of neovascularization.

High-density cell systems incorporating polymer microspheres as microenvironmental regulators in engineered cartilage tissues

To address the significant clinical need for tissue-engineered therapies for the repair and regeneration of articular cartilage, many systems have recently been developed using bioactive polymer microspheres as regulators of the chondrogenic microenvironment within high-density cell cultures. In this review, we highlight various densely cellular systems utilizing polymer microspheres as three-dimensional (3D) structural elements within developing engineered cartilage tissue, carriers for cell expansion and delivery, vehicles for spatiotemporally controlled growth factor delivery, and directors of cell behavior via regulation of cell-biomaterial interactions. The diverse systems described herein represent a shift from the more traditional tissue engineering approach of combining cells and growth factors within a biomaterial scaffold, to the design of modular systems that rely on the assembly of cells and bioactive polymer microspheres as building blocks to guide the creation of articular cartilage. Cell-based assembly of 3D microsphere-incorporated structures represents a promising avenue for the future of tissue engineering.

Preparation and in vitro characterisation of Ehrlichia ruminantium plasmid DNA and proteins encapsulated into and DNA adsorbed onto biodegradable microparticles

Four E. ruminantium 1H12 open reading frames and their proteins known to protect sheep against heartwater needle challenge were encapsulated into, or adsorbed onto poly(d,l-lactide-co-glycolide) microparticles. Microspheres with smooth surface and smaller than 5 μm diameters were produced, with high adsorption and encapsulation efficiencies. Gel electrophoresis showed that neither encapsulation nor adsorption affected the stability of the DNA or proteins. Cationic microparticles released ∼40% of plasmid DNA on day 1 while PLGA 50:50-COOH microparticles co-encapsulating plasmid DNA and polyvinyl alcohol only started to release from days 12-28. Recombinant proteins were released from PLGA 85:15 and homopolymer R 203 S microparticles in a biphasic manner with a high initial burst release (∼45-80%). In contrast, PLGA 50:50 microparticles had low (15-65%) initial burst release followed by (25-80%) release by days (days 28-42). A cocktail of these microparticles could therefore be used as single-dose auto-booster vaccine.

Progress in depsipeptide-based biomaterials

Polydepsipeptides - alternating copolymers of an alpha-amino acid and an alpha-hydroxy acid - are a group of biodegradable polymers. Versatile polydepsipeptides with or without pendant functional groups, as well as various polymer architectures, for example, providing alternative, random, diblock, triblock, multiblock or graft sequence structures, can be synthesized via ring-opening copolymerization of various morpholine-2,5-dione derivatives. They are potential candidates for a wide range of biomedical applications. Polydepsipeptides are described in this review from the aspect of materials science, especially as biomaterials. We mainly focus on various techniques developed to synthesize polydepsipeptides and their copolymers, biodegradation behaviors, shape-memory properties and possible biomedical applications.

Granulocyte colony-stimulating factor enhances cellular proliferation and motor function recovery on rats subjected to traumatic brain injury

OBJECTIVE

Traumatic brain injury (TBI) results in neurological dysfunction and death through primary or secondary mechanisms. Here, we evaluated the effect of osmotic pump delivery of granulocyte colony-stimulating factor (G-CSF) on the histopathology and motor function recovery of rats after experimental TBI.

METHODS

Sprague-Dawley rats were used as experimental model by fluid percussion device to cause brain injury on the motor cortex area. The rats were simultaneously subjected to TBI and were implanted of min-osmotic pump containing recombinant human G-CSF (300 μg/700 μl) via intraperitoneal injection. Motor function was assessed by rotarod test. 5-bromo-2'-deoxyuridine (BrdU) was used to label the proliferating cells and their differentiation was evaluated by histology and immunohistochemistry.

RESULTS

The G-CSF group showed significantly better motor function recovery than the control group, and the effect lasted up to 14 days after TBI. Moreover, the G-CSF group exhibited a greater increase in the number of BrdU-positive cells compared with the control group. The G-CSF group also had a significantly higher number of DCX-positive cells in the ipsilateral subventricular zone (SVZ) than the control group.

CONCLUSIONS

These data suggest that the beneficial effect of delivering G-CSF via an osmotic pump may improve the motor function and enhance neurogenesis in the SVZ of the injured brain.

Central nervous system delivery of large molecules: challenges and new frontiers for intrathecally administered therapeutics

IMPORTANCE OF THE FIELD

Therapeutic proteins and DNA constructs offer promise for the treatment of central nervous system disorders, yet significant biological barriers limit the ability of these molecules to reach the central nervous system from the bloodstream. Direct administrations to the cerebrospinal fluid (intrathecal administration) comprise an emerging field to facilitate the efficient delivery of these biological macromolecules to central nervous system tissues.

AREAS COVERED IN THIS REVIEW

Previous reports from 1990 to the present time describing the interactions and turnover of the cerebrospinal fluid within the intrathecal space, characterizations of the effects that therapeutic proteins and DNA have shown after intrathecal delivery through a lumbar route, and reports of emerging technologies to address the limitations of intrathecally administered macromolecules are reviewed.

WHAT THE READER WILL GAIN

This review provides an overview of the limitations that must be overcome for intrathecally administered biological macromolecules and the recent advances and promising approaches for surmounting these limitations.

TAKE HOME MESSAGE

Emerging approaches that stabilize and sustain the delivery of intrathecally administered biological macromolecules may enhance substantially the clinical relevance of promising therapeutic proteins and DNA constructs for the treatment of various central nervous system disorders.

Gene delivery by surface immobilization of plasmid to tissue-engineering scaffolds

Biomaterial scaffolds that serve as vehicles for gene delivery to promote expression of inductive factors have numerous regenerative medicine applications. In this report, we investigate plasmid delivery from biomaterial scaffolds using a surface immobilization strategy. Porous scaffolds were fabricated from poly(D,L-lactide-co-glycolide) (PLG), and plasmids were immobilized by drying. In vitro plasmid release indicated that the majority (>70%) of adsorbed plasmids were released within 24 h and >98% within 3 days; however, in vivo implantation of the scaffolds at the subcutaneous site yielded transgene expression that persisted for at least 28 weeks and was localized to the site of implantation. Histological analysis of DNA-adsorbed scaffolds indicated that macrophages at the scaffold were transfected in the first 2 weeks after implantation, whereas muscle cells adjacent to the implant primarily expressed the transgene at 4 weeks. In addition to localized gene expression, a secreted protein (human factor IX) was retained at the implant site and not available systemically after 3 days, indicating minimal off-target effects. These findings show that surface immobilization of plasmid onto microporous PLG scaffolds can produce localized and long-term gene expression in vivo, which may be used to enhance the bioactivity of scaffolds used for regenerative medicine.

Peptides that mimic the amino-terminal end of the rabies virus phosphoprotein have antiviral activity

We wanted to develop a therapeutic approach against rabies disease by targeting the lyssavirus transcription/replication complex. Because this complex (nucleoprotein N-RNA template processed by the L polymerase and its cofactor, the phosphoprotein P) is similar to that of other negative-strand RNA viruses, we aimed to design broad-spectrum antiviral drugs that could be used as a complement to postexposure vaccination and immunotherapy. Recent progress in understanding the structure/function of the rabies virus P, N, and L proteins predicts that the amino-terminal end of P is an excellent target for destabilizing the replication complex because it interacts with both L (for positioning onto the N-RNA template) and N (for keeping N soluble, as needed for viral RNA encapsidation). Thus, peptides mimicking various lengths of the amino-terminal end of P have been evaluated, as follows: (i) for binding properties to the N-P-L partners by the two-hybrid method; (ii) for their capacity to inhibit the transcription/replication of a rabies virus minigenome encoding luciferase in BHK-21-T7 cells; and (iii) for their capacity to inhibit rabies virus infection of BHK-21-T7 cells and of two derivatives of the neuronal SK-N-SH cell line. Peptides P60 and P57 (the first 60 and first 57 NH2 residues of P, respectively) exhibited a rapid, strong, and long-lasting inhibitory potential on luciferase expression (>95% from 24 h to 55 h). P42 was less efficient in its inhibition level (75% for 18 to 30 h) and duration (40% after 48 h). The most promising peptides were synthesized in tandem with the Tat sequence, allowing cell penetration. Their inhibitory effects were observed on BHK-21-T7 cells infected with rabies virus and Lagos bat virus but not with vesicular stomatitis virus. In neuronal cells, a significant inhibition of both nucleocapsid inclusions and rabies virus release was observed.

A guidance channel seeded with autologous Schwann cells for repair of cauda equina injury in a primate model

BACKGROUND/OBJECTIVE

To evaluate an implantable guidance channel (GC) seeded with autologous Schwann cells to promote regeneration of transected spinal nerve root axons in a primate model.

METHODS

Schwann cells were obtained from sural nerve segments of monkeys (Macaca fascicularis; cynomolgus). Cells were cultured, purified, and seeded into a PAN/PVC GC. Approximately 3 weeks later, monkeys underwent laminectomy and dural opening. Nerve roots of the L4 through L7 segments were identified visually. The threshold voltage needed to elicit hindlimb muscle electromyography (EMG) after stimulation of intact nerve roots was determined. Segments of 2 or 3 nerve roots (each approximately 8-15 mm in length) were excised. The GC containing Schwann cells was implanted between the proximal and distal stumps of these nerve roots and attached to the stumps with suture. Follow-up evaluation was conducted on 3 animals, with survival times of 9 to 14 months.

RESULTS

Upon reexposure of the implant site, subdural nerve root adhesions were noted in all 3 animals. Several of the implanted GC had collapsed and were characterized by thin strands of connective tissue attached to either end. In contrast, 3 of the 8 implanted GC were intact and had white, glossy cables entering and exiting the conduits. Electrical stimulation of the tissue cable in each of these 3 cases led to low-threshold evoked EMG responses, suggesting that muscles had been reinnervated by axons regenerating through the repair site and into the distal nerve stump. During harvesting of the GC implant, sharp transection led to spontaneous EMG in the same 3 roots showing a low threshold to electrical stimulation, whereas no EMG was seen when harvesting nerve roots with high thresholds to elicit EMG. Histology confirmed large numbers of myelinated axons at the midpoint of 2 GC judged to have reinnervated target muscles.

CONCLUSIONS

We found a modest rate of successful regeneration and muscle reinnervation after treatment of nerve root transection with a Schwann cell-seeded, implanted synthetic GC. Newer treatments, which include the use of absorbable polymers, neurotrophins, and antiscar agents, may further improve spinal nerve regeneration for repair of cauda equina injury.

Affinity-based release of glial-derived neurotrophic factor from fibrin matrices enhances sciatic nerve regeneration

Glial-derived neurotrophic factor (GDNF) promotes both sensory and motor neuron survival. The delivery of GDNF to the peripheral nervous system has been shown to enhance regeneration following injury. In this study, we evaluated the effect of affinity-based delivery of GDNF from a fibrin matrix in a nerve guidance conduit on nerve regeneration in a 13 mm rat sciatic nerve defect. Seven experimental groups were evaluated which received GDNF or nerve growth factor (NGF) with the delivery system within the conduit, control groups excluding one or more components of the delivery system, and nerve isografts. Nerves were harvested 6 weeks after treatment for analysis by histomorphometry and electron microscopy. The use of the delivery system (DS) with either GDNF or NGF resulted in a higher frequency of nerve regeneration vs. control groups, as evidenced by a neural structure spanning the 13 mm gap. The GDNF DS and NGF DS groups were also similar to the nerve isograft group in measures of nerve fiber density, percent neural tissue and myelinated area measurements, but not in terms of total fiber counts. In addition, both groups contained a significantly greater percentage of larger diameter fibers, with GDNF DS having the largest in comparison to all groups, suggesting more mature neural content. The delivery of GDNF via the affinity-based delivery system can enhance peripheral nerve regeneration through a silicone conduit across a critical nerve gap and offers insight into potential future alternatives to the treatment of peripheral nerve injuries.

Localized cell and drug delivery for auditory prostheses

Localized cell and drug delivery to the cochlea and central auditory pathway can improve the safety and performance of implanted auditory prostheses (APs). While generally successful, these devices have a number of limitations and adverse effects including limited tonal and dynamic ranges, channel interactions, unwanted stimulation of non-auditory nerves, immune rejection, and infections including meningitis. Many of these limitations are associated with the tissue reactions to implanted auditory prosthetic devices and the gradual degeneration of the auditory system following deafness. Strategies to reduce the insertion trauma, degeneration of target neurons, fibrous and bony tissue encapsulation, and immune activation can improve the viability of tissue required for AP function as well as improve the resolution of stimulation for reduced channel interaction and improved place-pitch and level discrimination. Many pharmaceutical compounds have been identified that promote the viability of auditory tissue and prevent inflammation and infection. Cell delivery and gene therapy have provided promising results for treating hearing loss and reversing degeneration. Currently, many clinical and experimental methods can produce extremely localized and sustained drug delivery to address AP limitations. These methods provide better control over drug concentrations while eliminating the adverse effects of systemic delivery. Many of these drug delivery techniques can be integrated into modern auditory prosthetic devices to optimize the tissue response to the implanted device and reduce the risk of infection or rejection. Together, these methods and pharmaceutical agents can be used to optimize the tissue-device interface for improved AP safety and effectiveness.