Synthesis, Characterization, Biodegradation, and Drug Delivery Application of Biodegradable Lactic/Glycolic Acid Polymers: Part III. Drug Delivery Application

Injectable long-acting ivacaftor-loaded poly (lactide-co-glycolide) microparticle formulations for the treatment of cystic fibrosis: In vitro characterization and in vivo pharmacokinetics in mice

Optimizing a sustained-release drug delivery system for the treatment of cystic fibrosis (CF) is crucial for decreasing the dosing frequency and improving patients' compliance with the treatment regimen. In the current work, we developed an injectable poly(D,L-lactide-co-glycolide) (PLGA) microparticle formulation loaded with ivacaftor, a cystic fibrosis transmembrane conductance regulator (CFTR) potentiator that increases the open probability of the CFTR anion channel, using a single emulsion solvent evaporation technique. We aimed to study the effect of different parameters on the characteristics of the prepared formulations to select an optimized microparticle formulation to be used in an in vivo pharmacokinetic study in mice. First, a suite of ivacaftor-loaded microparticles were prepared using different formulation parameters in order to study the effect of varying these parameters on microparticle size, morphology, drug loading, encapsulation efficiency, and in vitro release profiles. Prepared microparticles were spherical with diameters ranging from 1.91-6.93 µm, percent drug loading (% DL) of 3.91-10.3%, percent encapsulation efficiencies (% EE) of 26.6-100%, and an overall slow cumulative release profile. We selected the formulation that demonstrated optimal combined % DL and % EE values (8.25 and 90.7%, respectively) for further studies. These microparticles had an average particle size of 6.83 µm and a slow tri-phasic in vitro release profile (up to 6 weeks). In vivo pharmacokinetic studies in mice showed that the subcutaneously injected microparticles resulted in steady plasma levels of ivacaftor over a period of 28 days, and a 6-fold increase in AUC 0 - t (71.6 µg/mL*h) compared to the intravenously injected soluble ivacaftor (12.3 µg/mL*h). Our results suggest that this novel ivacaftor-loaded microparticle formulation could potentially eliminate the need for the frequent daily administration of ivacaftor to people with CF thus improving their compliance and ensuring successful treatment outcomes.

In Vitro/In Vivo Preparation and Evaluation of cRGDyK Peptide-Modified Polydopamine-Bridged Paclitaxel-Loaded Nanoparticles

Cancer remains a disease with one of the highest mortality rates worldwide. The poor water solubility and tissue selectivity of commonly used chemotherapeutic agents contribute to their poor efficacy and serious adverse effects. This study proposes an alternative to the traditional physicochemically combined modifications used to develop targeted drug delivery systems, involving a simpler surface modification strategy. cRGDyK peptide (RGD)-modified PLGA nanoparticles (NPs) loaded with paclitaxel were constructed by coating the NP surfaces with polydopamine (PD). The average particle size of the produced NPs was 137.6 ± 2.9 nm, with an encapsulation rate of over 80%. In vitro release tests showed that the NPs had pH-responsive drug release properties. Cellular uptake experiments showed that the uptake of modified NPs by tumor cells was significantly better than that of unmodified NPs. A tumor cytotoxicity assay demonstrated that the modified NPs had a lower IC50 and greater cytotoxicity than those of unmodified NPs and commercially available paclitaxel formulations. An in vitro cytotoxicity study indicated good biosafety. A tumor model in female BALB/c rats was established using murine-derived breast cancer 4T1 cells. RGD-modified NPs had the highest tumor-weight suppression rate, which was higher than that of the commercially available formulation. PTX-PD-RGD-NPs can overcome the limitations of antitumor drugs, reduce drug toxicity, and increase efficacy, showing promising potential in cancer therapy.

An Overview of Scaffolds and Biomaterials for Skin Expansion and Soft Tissue Regeneration: Insights on Zinc and Magnesium as New Potential Key Elements

The utilization of materials in medical implants, serving as substitutes for non-functional biological structures, supporting damaged tissues, or reinforcing active organs, holds significant importance in modern healthcare, positively impacting the quality of life for millions of individuals worldwide. However, certain implants may only be required temporarily to aid in the healing process of diseased or injured tissues and tissue expansion. Biodegradable metals, including zinc (Zn), magnesium (Mg), iron, and others, present a new paradigm in the realm of implant materials. Ongoing research focuses on developing optimized materials that meet medical standards, encompassing controllable corrosion rates, sustained mechanical stability, and favorable biocompatibility. Achieving these objectives involves refining alloy compositions and tailoring processing techniques to carefully control microstructures and mechanical properties. Among the materials under investigation, Mg- and Zn-based biodegradable materials and their alloys demonstrate the ability to provide necessary support during tissue regeneration while gradually degrading over time. Furthermore, as essential elements in the human body, Mg and Zn offer additional benefits, including promoting wound healing, facilitating cell growth, and participating in gene generation while interacting with various vital biological functions. This review provides an overview of the physiological function and significance for human health of Mg and Zn and their usage as implants in tissue regeneration using tissue scaffolds. The scaffold qualities, such as biodegradation, mechanical characteristics, and biocompatibility, are also discussed.

Poly (Lactic-Co-Glycolic) Acid–Poly (Vinyl Pyrrolidone) Hybrid Nanoparticles to Improve the Efficiency of Oral Delivery of β-Carotene

The aim of this study was to develop a nanoparticle formulation made of poly (vinyl pyrrolidone) (PVP) and poly (lactic-co-glycolic) acid (PLGA) for the oral delivery of β-carotene (BC). The hybrid nanoparticles were prepared by the interfacial deposition method, and the physicochemical properties of this formulation were characterized in terms of its morphology, particle size, size distribution, encapsulation efficiency, dissolution, intestinal permeability, and in vivo pharmacokinetics. Our results demonstrated that BC-loaded nanoformulation and PLGA nanoparticles (PNP) significantly enhanced a release 6.1 times higher than BC suspension. The fortification of PVP into PLGA nanoparticles, named PLGA–PVP hybrid nanoparticles (PPNP), significantly reduced the particle size, as well as led to an increase 1.9 times higher in the in vitro release of BC, compared with PNP. For the ex vivo intestinal permeability assessment, PNP and PPNP–K15 significantly enhanced the intestinal permeability by 2.7 and 6.5 times at the jejunum, and 2.3 and 4.5 times at the ileum, when compared with unformulated BC. According to the pharmacokinetic study, the optimized hybrid formulation significantly increased the peak plasma concentration (C_max) and the area under the curve (AUC_0-t), and the oral relative bioavailability showed a five-fold enhancement compared with that of the BC suspension. Our results indicate that the hybrid nanoparticulate delivery system is an efficient strategy for the oral delivery of BC.

Antibacterial and Fluorescence Staining Properties of an Innovative GTR Membrane Containing 45S5BGs and AIE Molecules In Vitro

This study aimed to add two functional components-antibacterial 45S5BGs particles and AIE nanoparticles (TPE-NIM⁺) with bioprobe characteristics-to the guided tissue regeneration (GTR) membrane, to optimize the performance. The PLGA/BG/TPE-NIM⁺ membrane was synthesized. The static water contact angle, morphologies, and surface element analysis of the membrane were then characterized. In vitro biocompatibility was tested with MC3T3-E1 cells using CCK-8 assay, and antibacterial property was evaluated with Streptococcus mutans and Porphyromonas gingivalis by the LIVE/DEAD bacterial staining and dilution plating procedure. The fluorescence staining of bacteria was observed by Laser Scanning Confocal Microscope. The results showed that the average water contact angle was 46°. In the cytotoxicity test, except for the positive control group, there was no significant difference among the groups (p > 0.05). The antibacterial effect in the PLGA/BG/TPE-NIM⁺ group was significantly (p < 0.01), while the sterilization rate was 99.99%, better than that in the PLGA/BG group (98.62%) (p < 0.01). Confocal images showed that the membrane efficiently distinguished G⁺ bacteria from G^- bacteria. This study demonstrated that the PLGA/BG/TPE-NIM⁺ membrane showed good biocompatibility, efficient sterilization performance, and surface mineralization ability and could be used to detect pathogens in a simple, fast, and wash-free protocol.

Directional Growth of cm-Long PLGA Nanofibers by a Simple and Fast Wet-Processing Method

The development of aligned nanofibers as useful scaffolds for tissue engineering is an actively sought-for research objective. Here, we propose a novel improvement of an existing self-assembly-based nanofabrication technique (ASB-SANS). This improvement, which we termed Directional ASB-SANS, allows one to produce cm²-large domains of highly aligned poly(lactic-co-glycolic acid) (PLGA) nanofibers in a rapid, inexpensive, and easy way. The so-grown aligned PLGA nanofibers exhibited remarkable adhesion to different substrates (glass, polyimide, and Si/SiOx), even when immersed in PBS solution and kept at physiological temperature (37 °C) for up to two weeks. Finally, the Directional ASB-SANS technique allowed us to grow PLGA fibers also on highly heterogeneous substrates such as polyimide-based, gold-coated flexible electrodes. These results suggest the viability of Directional ASB-SANS method for realizing biocompatible/bioresorbable, nanostructured coatings, potentially suitable for neural interface systems.

Drug release from in situ forming implants and advances in release testing

In situ forming implants, defined as liquid formulations that generate solid or semisolid depots following administration, have shown a range of advantages in drug delivery. This drug delivery strategy allows localized delivery, sustained drug release over periods of days to months, and is a less invasive option compared to traditional solid implants which typically require surgical implantation. Unfortunately, there are a number of quality control challenges in terms of drug release testing of these delivery systems which is likely to have contributed to the relatively few commercially available in situ forming implant products. This article reviews current marketed in situ forming implant products, FDA guidance on in vitro release testing, and formulation and environmental parameters influencing drug release from in situ forming implants. Formulation considerations for development of biological agents loaded in situ forming implants are also discussed. The advantages and limitations of typically used in vitro release testing methods are summarized. Difficulties in the development of in vitro-in vivo correlations (IVIVCs) for in situ forming implant are discussed. The knowledge presented will be helpful for the development of in situ forming implants, as well as for the development of appropriate in vitro testing methods and IVIVCs.

Zero-order drug delivery: State of the art and future prospects

Pharmaceutical drugs are an important part of the global healthcare system, with some estimates suggesting over 50% of the world's population takes at least one medication per day. Most drugs are delivered as immediate-release formulations that lead to a rapid increase in systemic drug concentration. Although these formulations have historically played an important role, they can be limited by poor patient compliance, adverse side effects, low bioavailability, or undesirable pharmacokinetics. Drug delivery systems featuring first-order release kinetics have been able to improve pharmacokinetics but are not ideal for drugs with short biological half-lives or small therapeutic windows. Zero-order drug delivery systems have the potential to overcome the issues facing immediate-release and first-order systems by releasing drug at a constant rate, thereby maintaining drug concentrations within the therapeutic window for an extended period of time. This release profile can be used to limit adverse side effects, reduce dosing frequency, and potentially improve patient compliance. This review covers strategies being employed to attain zero-order release or alter traditionally first-order release kinetics to achieve more consistent release before discussing opportunities for improving device performance based on emerging materials and fabrication methods.

Effect of Polymer Permeability and Solvent Removal Rate on In Situ Forming Implants: Drug Burst Release and Microstructure

To explore the mechanism of drug release and depot formation of in situ forming implants (ISFIs), osthole-loaded ISFIs were prepared by dissolving polylactide, poly(lactide-co-glycolide), polycaprolactone, or poly(trimethylene carbonate) in different organic solvents, including N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), and triacetin (TA). Drug release, polymer degradation, solvent removal rate and depot microstructure were examined. The burst release effect could be reduced by using solvents exhibit slow forming phase inversion and less permeable polymers. Both the drug burst release and polymer depot microstructure were closely related to the removal rate of organic solvent. Polymers with higher permeability often displayed faster drug and solvent diffusion rates. Due to high polymer-solvent affinity, some of the organic solvent remained in the depot even after the implant was completely formed. The residual of organic solvent could be predicted by solubility parameters. The ISFI showed a lower initial release in vivo than that in vitro. In summary, the effects of different polymers and solvents on drug release and depot formation in ISFI systems were extensively investigated and discussed in this article. The two main factors, polymer permeability and solvent removal rate, were involved in different stages of drug release and depot formation in ISFI systems.

Submicron-Sized Nanocomposite Magnetic-Sensitive Carriers: Controllable Organ Distribution and Biological Effects

Although new drug delivery systems have been intensely developed in the past decade, no significant increase in the efficiency of drug delivery by nanostructure carriers has been achieved. The reasons are the lack of information about acute toxicity, the influence of the submicron size of the carrier and difficulties with the study of biodistribution in vivo. Here we propose, for the first time in vivo, new nanocomposite submicron carriers made of bovine serum albumin (BSA) and tannic acid (TA) and containing magnetite nanoparticles with sufficient content for navigation in a magnetic field gradient on mice. We examined the efficacy of these submicron carriers as a delivery vehicle in combination with magnetite nanoparticles which were systemically administered intravenously. In addition, the systemic toxicity of this carrier for intravenous administration was explicitly studied. The results showed that (BSA/TA) carriers in the given doses were hemocompatible and didn’t cause any adverse effect on the respiratory system, kidney or liver functions. A combination of gradient-magnetic-field controllable biodistribution of submicron carriers with fluorescence tomography/MRI imaging in vivo provides a new opportunity to improve drug delivery efficiency.

A method of elevated temperatures coupled with magnetic stirring to predict real time release from long acting progesterone PLGA microspheres

The object of the study was to develop a quick and reproducible accelerated in vitro release method to predict and deduce the function of the real time (37 °C) release for long acting PLGA microspheres. The method could be described in several steps. First, the release of the microspheres were studied using the sample and separate method at 37 °C with normal orbital shaking and elevated temperatures with magnetic stirring to further accelerate the release. Second, the most similar profile at elevated temperatures with the real time release was chosen with the help of the n value in the fitted Korsmeyer-Peppas Function. Third, the Weibull function and conversion ratio were used to deduce the function of real time release according to the chosen profile at elevated temperatures. The key point in this study was to provide a quick and precise method to predict the real time release for long acting progesterone PLGA microspheres. So the elevated temperatures coupled with magnetic stirring were used to accelerate the release further, and when there have many similar release profiles with the real time release at elevated temperatures, releasing time at elevated temperatures and the R2 of the final deduced function will be used to help choosing the most similar release profile with the real time release. Four different types of progesterone PLGA microspheres were used to verify the method, and all the deduced function correlated well with the real time releases, for R 2  = 0.9912, 0.9781, 0.9918 and 0.9972, respectively.

Poly(lactic-co-glycolic acid) devices: Production and applications for sustained protein delivery

Injectable or implantable poly(lactic-co-glycolic acid) (PLGA) devices for the sustained delivery of proteins have been widely studied and utilized to overcome the necessity of repeated administrations for therapeutic proteins due to poor pharmacokinetic profiles of macromolecular therapies. These devices can come in the form of microparticles, implants, or patches depending on the disease state and route of administration. Furthermore, the release rate can be tuned from weeks to months by controlling the polymer composition, geometry of the device, or introducing additives during device fabrication. Slow-release devices have become a very powerful tool for modern medicine. Production of these devices has initially focused on emulsion-based methods, relying on phase separation to encapsulate proteins within polymeric microparticles. Process parameters and the effect of additives have been thoroughly researched to ensure protein stability during device manufacturing and to control the release profile. Continuous fluidic production methods have also been utilized to create protein-laden PLGA devices through spray drying and electrospray production. Thermal processing of PLGA with solid proteins is an emerging production method that allows for continuous, high-throughput manufacturing of PLGA/protein devices. Overall, polymeric materials for protein delivery remain an emerging field of research for the creation of single administration treatments for a wide variety of disease. This review describes, in detail, methods to make PLGA devices, comparing traditional emulsion-based methods to emerging methods to fabricate protein-laden devices. This article is categorized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Implantable Materials and Surgical Technologies > Nanomaterials and Implants Biology-Inspired Nanomaterials > Peptide-Based Structures.

Nano-encapsulated HHC10 host defense peptide (HDP) reduces the growth of Escherichia coli via multimodal mechanisms

The eradication of several pathogenic drug resistant "Superbug" such as Escherichia coli became difficult especially in chronic infections using existing antibiotics due to the emergence of antibiotic resistance. Owing to their unique antibacterial properties, host defense peptides (HDP) have gained significant attention to combat colonization of bacteria. This study aims designing delivery systems for HHC10 peptide to target bacteria inside the cells might be a promising approach by protecting from degradation, controlling the release, enhancing the susceptibility of target microbes and improving bioavailability. Nano-formulated HHC10 was evaluated for its efficacy (CFU assay) and possible mechanism of action (membrane interaction and apoptosis) against E. coli. Dose-dependent inhibition of E. coli growth is observed for nano-encapsulated and bare HHC10 and encapsulated form remain non-toxic to macrophage mouse cells (RAW264.6) up to 20 μM. Mechanistic analyses using transmission electron microscopy and flow cytometry techniques revealed that bactericidal activity of HHC10-NP progresses via a multimodal mechanism of bacterial cell death by cell-membrane lysis on direct interaction with bacteria while through induction of the apoptotic death pathway inside the host cells. These results offer an insight on future strategies for the development and application of antimicrobial peptides as antibacterial alternatives. Controlled delivery of HHC10 peptide from PLGA-NP kills bacteria by two different mechanism: (i) direct killing: HHC10 disintegrate the cell membrane of bacteria by electrostatic interactions and (ii) indirect killing: induction of apoptosis in bacteria infect cells.

Preparation of TPP-crosslinked chitosan microparticles by spray drying for the controlled delivery of progesterone intended for estrus synchronization in cattle

PURPOSE

Planned reproduction in cattle involves regulation of estrous cycle and the use of artificial insemination. Cycle control includes the administration of exogenous progesterone during 5-8 days in a controlled manner allowing females to synchronize their ovulation. Several progesterone delivery systems are commercially available but they have several drawbacks. The aim of the present contribution was to evaluate chitosan microparticles entrapping progesterone as an alternative system.

METHODS

Microparticles were prepared by spray drying. The effect of formulation parameters and experimental conditions on particle features and delivery was studied. A mathematical model to predict progesterone plasma concentration in animals was developed and validated with experimental data.

RESULTS

Microparticle size was not affected by formulation parameters but sphericity enhances as Tween 80 content increases and it impairs as TPP content rises. Z potential decreases as phosphate content rises. Particles remain stable in acidic solution but the addition of surfactant is required to stabilize dispersions in neutral medium. Encapsulation efficiencies was 69-75%. In vitro delivery studies showed burst and diffusion-controlled phases, being progesterone released faster at low pH. In addition, delivery extend in cows was affected mainly by particle size and hormone initial content, while the amount injected altered plasma concentration. Theoretical predictions with excellent accuracy were obtained.

CONCLUSION

The mathematical model developed can help to find proper particle features to reach specific delivery rates in the animals. This not only save time, money and effort but also minimized experimentation with animals which is desired from an ethical point of view.

Formulation and Pharmacokinetics of HSA-core and PLGA-shell Nanoparticles for Delivering Gemcitabine

Gemcitabine-loaded core-shell nanoparticles (CSNPs), comprised of a cross-linked HSA-core and PLGA-shell, were prepared through a modified double emulsification method, and the processing parameters were systematically investigated. The optimized CSNPs had a particle size of 241 ± 36.2 nm and an encapsulation efficiency of 41.52%. The core-shell structure was characterized by optical microscope (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The amorphous nature of the encapsulated drug was confirmed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). An in vitro release study demonstrated that the CSNPs had an improved sustained release profile controlled by erosion of materials in combination with drug diffusion. In vivo pharmacokinetics of CSNPs obtained a bigger area under concentration-time curve (AUC), t _1/2, and C _max compared to free drug solution. The results suggest that HSA-PLGA-based CSNPs can be a promising carrier for the sustained release of gemcitabine.

Preparation, characterization and immunological evaluation of alginate nanoparticles loaded with whole inactivated influenza virus: Dry powder formulation for nasal immunization in rabbits

It has become important to explore more efficient and feasible influenza vaccines, since epidemics of influenza virus cause hundreds of thousands of deaths all around the world. Improving immunogenicity of parentral influenza vaccines has given rise to mucosal delivery routes. In this study, alginate nanoparticles (NPs) were efficiently synthetized by ionic gelation method and influenza virus and CpG ODN or Quillaja Saponin (QS) adjuvants were actively incorporated into alginate NPs. The prepared particles were evaluated for both humoral and cellular immune responses in rabbits' nostrils. The vaccination started with a prime dose and followed by three boosters (two intranasal (IN) on days 45 and 60 and the last dose, intramuscular (IM) on day 75). HAI titer had increased in all the samples; although, only in the group received WV + CPG suspension reached to the protective HAI titer. All the immunized rabbits elicited significantly high sIgA levels on day 75, compared to the negative and the IM groups. At the end of the study, IN administration of CpG ODN adjuvant with virus antigen induced higher IgG level than the groups vaccinated with alginate NPs with or without CpG ODN (P < 0.001). As for the cellular immunity, CpG ODN was capable of inducing significant levels of IL-4 and TNF-α, either through inoculation along with the virus suspension or as incorporated in alginate NPs. According to the obtained data, CpG ODN adjuvant showed higher immunogenic potential as part of a vaccine delivery system than QS. Moreover, applying alginate polymer as a nasal delivery system carrier was not deemed immunogenic against influenza whole virus.

Nanoparticulate delivery of agents for induced elastogenesis in three-dimensional collagenous matrices

The degradation of elastic matrix in the infrarenal aortic wall is a critical parameter underlying the formation and progression of abdominal aortic aneurysms. It is mediated by the chronic overexpression of matrix metalloprotease (MMP)-2 and MMP-9, leading to a progressive loss of elasticity and weakening of the aortic wall. Delivery of therapeutic agents to inhibit MMPs, while concurrently coaxing cell-based regenerative repair of the elastic matrix represents a potential strategy for slowing or arresting abdominal aortic aneurysm growth. Previous studies have demonstrated elastogenic induction of healthy and aneurysmal aortic smooth muscle cells and inhibition of MMPs, following exogenous delivery of elastogenic factors such as transforming growth factor (TGF)-β1, as well as MMP-inhibitors such as doxycycline (DOX) in two-dimensional culture. Based on these findings, and others that demonstrated elastogenic benefits of nanoparticulate delivery of these agents in two-dimensional culture, poly(lactide-co-glycolide) nanoparticles were developed for localized, controlled and sustained delivery of DOX and TGF-β1 to human aortic smooth muscle cells within a three-dimensional gels of type I collagen, which closely simulate the arterial tissue microenvironment. DOX and TGF-β1 released from these nanoparticles influenced elastogenic outcomes positively within the collagen constructs over 21 days of culture, which were comparable to that induced by exogenous supplementation of DOX and TGF-β1 within the culture medium. However, this was accomplished at doses ~20-fold lower than the exogenous dosages of the agents, illustrating that their localized, controlled and sustained delivery from nanoparticles embedded within a three-dimensional scaffold is an efficient strategy for directed elastogenesis. Copyright © 2014 John Wiley & Sons, Ltd.

Mesenchymal stem cells and alginate microcarriers for craniofacial bone tissue engineering: A review

Craniofacial bone is a complex structure with an intricate anatomical and physiological architecture. The defects that exist in this region therefore require a precise control of osteogenesis in their reconstruction. Unlike traditional surgical intervention, tissue engineering techniques mediate bone development with limited postoperative risk and cost. Alginate stands as the premier polymer in bone repair because of its mild ionotropic gelation and excellent biocompatibility, biodegradability, and injectability. Alginate microcarriers are candidates of choice to mediate cells and accommodate into 3-D environment. Several studies reported the use of alginate microcarriers for delivering cells, drugs, and growth factors. This review will explore the potential use of alginate microcarrier for stem cell systems and its application in craniofacial bone tissue engineering.

Microspheres prepared with different co-polymers of poly(lactic-glycolic acid) (PLGA) or with chitosan cause distinct effects on macrophages

Microencapsulation of bioactive molecules for modulating the immune response during infectious or inflammatory events is a promising approach, since microspheres (MS) protect these labile biomolecules against fast degradation, prolong the delivery over longer periods of time and, in many situations, target their delivery to site of action, avoiding toxic side effects. Little is known, however, about the influence of different polymers used to prepare MS on macrophages. This paper aims to address this issue by evaluating in vitro cytotoxicity, phagocytosis profile and cytokines release from alveolar macrophages (J-774.1) treated with MS prepared with chitosan, and four different co-polymers of PLGA [poly (lactic-co-glycolic acid)]. The five MS prepared presented similar diameter and zeta potential each other. Chitosan-MS showed to be cytotoxic to J-774.1 cells, in contrast to PLGA-MS, which were all innocuous to this cell linage. PLGA 5000-MS was more efficiently phagocytized by macrophages compared to the other MS tested. PLGA 5000-MS and 5002-MS induced significant production of TNF-α, while 5000-MS, 5004-MS and 7502-MS decreased spontaneous IL-6 release. Nevertheless, only PLGA 5002-MS induced significant NFkB/SEAP activation. These findings together show that MS prepared with distinct PLGA co-polymers are differently recognized by macrophages, depending on proportion of lactic and glycolic acid in polymeric chain, and on molecular weight of the co-polymer used. Selection of the most adequate polymer to prepare a microparticulate drug delivery system to modulate immunologic system may take into account, therefore, which kind of immunomodulatory response is more adequate for the required treatment.

Polyactives: controlled and sustained bioactive release via hydrolytic degradation

Significant and promising advances have been made in the polymer field for controlled and sustained bioactive delivery. Traditionally, small molecule bioactives have been physically incorporated into biodegradable polymers; however, chemical incorporation allows for higher drug loading, more controlled release, and enhanced processability. Moreover, the advent of bioactive-containing monomer polymerization and hydrolytic biodegradability allows for tunable bioactive loading without yielding a polymer residue. In this review, we highlight the chemical incorporation of different bioactive classes into novel biodegradable and biocompatible polymers. The polymer design, synthesis, and formulation are summarized in addition to the evaluation of bioactivity retention upon release via in vitro and in vivo studies.

In vitro evaluation of suspoemulsions for in situ-forming polymeric microspheres and controlled release of progesterone

One possibility to obtain a higher dose of drug in a lower formulation volume can be by using of saturated quantity of drug in one of the phases of an emulsion. These formulations are called suspoemulsions (S/O/W). When a hydrophobic polymer is added to the organic phase of suspoemulsions, these formulations can be used to entrap the drug inside microspheres after in situ precipitation of the polymer-drug-excipients mix. In this work, performance and stability of progesterone suspensions in triacetin as organic phase of suspoemulsions were evaluated. These formulations were compared with O/W emulsions. Mathematical models were used to study in vitro release profiles. The results confirmed that S/O/W systems could be an attractive alternative to O/W formulations for the entrapment of progesterone inside poly(d,l-lactide-co-glycolide) microspheres. Diffusive-based models fit the in vitro release of progesterone from in situ-formed microspheres. For longer release periods, a time-dependent diffusion coefficient was successfully estimated.

Prostaglandin D2-loaded microspheres effectively activate macrophage effector functions

Biodegradable lactic-co-glycolic acid (PLGA) microspheres (MS) improve the stability of biomolecules stability and allow enable their sustained release. Lipid mediators represent a strategy for improving host defense; however, most of these mediators, such as prostaglandin D2 (PGD2), have low water solubility and are unstable. The present study aimed to develop and characterize MS loaded with PGD2 (PGD2-MS) to obtain an innovative tool to activate macrophages. PGD2-MS were prepared using an oil-in-water emulsion solvent extraction-evaporation process, and the size, zeta potential, surface morphology and encapsulation efficiency were determined. It was also evaluated in vitro the phagocytic index, NF-κB activation, as well as nitric oxide and cytokine production by alveolar macrophages (AMs) in response to PGD2-MS. PGD2-MS were spherical with a diameter of 5.0±3.3 μm and regular surface, zeta potential of -13.4±5.6 mV, and 36% of encapsulation efficiency, with 16-26% release of entrapped PGD2 at 4 and 48 h, respectively. PGD2-MS were more efficiently internalized by AMs than unloaded-MS, and activated NF-κB more than free PGD2. Moreover, PGD2-MS stimulated the production of nitric oxide, TNF-α, IL-1β, and TGF-β, more than free PGD2, indicating that microencapsulation increased the activating effect of PGD2 on cells. In LPS-pre-treated AMs, PGD2-MS decreased the release of IL-6 but increased the production of nitric oxide and IL-1β. These results show that the morphological characteristics of PGD2-MS facilitated interaction with, and activation of phagocytic cells; moreover, PGD2-MS retained the biological activities of PGD2 to trigger effector mechanisms in AMs. It is suggested that PGD2-MS represent a strategy for therapeutic intervention in the lungs of immunocompromised subjects.

Surface modification of poly(D,L-lactic acid) scaffolds for orthopedic applications: a biocompatible, nondestructive route via diazonium chemistry

Scaffolds made with synthetic polymers such as polyesters are commonly used in bone tissue engineering. However, their hydrophobicity and the lack of specific functionalities make their surface not ideal for cell adhesion and growth. Surface modification of these materials is thus crucial to enhance the scaffold's integration in the body. Different surface modification techniques have been developed to improve scaffold biocompatibility. Here we show that diazonium chemistry can be used to modify the outer and inner surfaces of three-dimensional poly(D,L-lactic acid) (PDLLA) scaffolds with phosphonate groups, using a simple two-step method. By changing reaction time and impregnation procedure, we were able to tune the concentration of phosphonate groups present on the scaffolds, without degrading the PDLLA matrix. To test the effectiveness of this modification, we immersed the scaffolds in simulated body fluid, and characterized them with scanning electron microscopy, X-ray photoelectron spectroscopy, Raman, and infrared spectroscopy. Our results showed that a layer of hydroxyapatite particles was formed on all scaffolds after 2 and 4 weeks of immersion; however, the precipitation was faster and in larger amounts on the phosphonate-modified than on the bare PDLLA scaffolds. Both osteogenic MC3T3-E1 and chondrogenic ATDC5 cell lines showed increased cell viability/metabolic activity when grown on a phosphonated PDLLA surface in comparison to a control PDLLA surface. Also, more calcium-containing minerals were deposited by cultures grown on phosphonated PDLLA, thus showing the pro-mineralization properties of the proposed modification. This work introduces diazonium chemistry as a simple and biocompatible technique to modify scaffold surfaces, allowing to covalently and homogeneously bind a number of functional groups without degrading the scaffold's polymeric matrix.

Synthesis of microwave-assisted poly(methyl vinyl ether-co-maleic anhydride)-bovine serum albumin bioconjugates

The water-soluble poly(methyl vinyl ether-co-maleic anhydride) copolymer-bovine serum albumin bioconjugates were synthesized in the presence of 1-ethyl-3-(3-dimetilamino-propyl) carbodiimide hydrochloride as cross-linking agents via microwave-assisted and conventional methods and characterized by size-exclusion chromatography and high-performance liquid chromatography. According to size-exclusion chromatography and high-performance liquid chromatography results, the bioconjugates synthesized in the microwave-assisted method are more stable and efficient than the conventional method. The reaction time is shortened from 17 hours to 15 minutes by means of the microwave-assisted method.