Degradable Polymer Microspheres for Controlled Drug Delivery

Recent advances in nano- and micro-scale carrier systems for controlled delivery of vaccines

Vaccines provide substantial safety against infectious diseases, saving millions of lives each year. The recent COVID-19 pandemic highlighted the importance of vaccination in providing mass-scale immunization against outbreaks. However, the delivery of vaccines imposes a unique set of challenges due to their large molecular size and low room temperature stability. Advanced biomaterials and delivery systems such as nano- and mciro-scale carriers are becoming critical components for successful vaccine development. In this review, we provide an updated overview of recent advances in the development of nano- and micro-scale carriers for controlled delivery of vaccines, focusing on carriers compatible with nucleic acid-based vaccines and therapeutics that emerged amid the recent pandemic. We start by detailing nano-scale delivery systems, focusing on nanoparticles, then move on to microscale systems including hydrogels, microparticles, and 3D printed microneedle patches. Additionally, we delve into emerging methods that move beyond traditional needle-based applications utilizing innovative delivery systems. Future challenges for clinical translation and manufacturing in this rapidly advancing field are also discussed.

Comparison between the Astaxanthin Release Profile of Mesoporous Bioactive Glass Nanoparticles (MBGNs) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/MBGN Composite Microspheres

In recent years, composite biomaterials have attracted attention for drug delivery applications due to the possibility of combining desired properties of their components. However, some functional characteristics, such as their drug release efficiency and likely side effects, are still unexplored. In this regard, controlled tuning of the drug release kinetic via the precise design of a composite particle system is still of high importance for many biomedical applications. This objective can be properly fulfilled through the combination of different biomaterials with unequal release rates, such as mesoporous bioactive glass nanoparticles (MBGN) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) microspheres. In this work, MBGNs and PHBV-MBGN microspheres, both loaded with Astaxanthin (ASX), were synthesised and compared in terms of ASX release kinetic, ASX entrapment efficiency, and cell viability. Moreover, the correlation of the release kinetic to phytotherapeutic efficiency and side effects was established. Interestingly, there were significant differences between the ASX release kinetic of the developed systems, and cell viability differed accordingly after 72 h. Both particle carriers effectively delivered ASX, though the composite microspheres exhibited a more prolonged release profile with sustained cytocompatibility. The release behaviour could be fine-tuned by adjusting the MBGN content in the composite particles. Comparatively, the composite particles induced a different release effect, implying their potential for sustained drug delivery applications.

COMPARİSON OF EGG WHİTE AND Ε-POLYCAPROLACTONE FOR THREE-DİMENSİONAL CELL CULTURE

It is increasingly becoming important to develop three-dimensional (3-D) cell culture systems due to their numerous advantages over traditional monolayer culture. The aim of this study is to investigate the interaction of adipose derived stem cells (ADSCs) with scaffolds composed of ε-polycaprolactone (ε-PCL) and egg white. In our study; ε-PCL and egg white scaffolds were fabricated from their monomers under the catalysis of tin octoate and by polymerization by heat respectively. Characterization of PCL was carried out with Gel permeability chromatography (GPC), Fourier Transform Infrared Spectrophotometry (FTIR), Proton Nuclear Magnetic Resonance (H-NMR), Differential Scan Calorimetry (DSC) and Scanning Electron Microscopy (SEM). CM-DiI labeled ADSCs were cultured for 12 days on egg white and ε-PCL scaffolds. Cell viability was performed using MTT and nitric oxide level was evaluated for toxicity. Results showed that the number of ADSCs on egg white scaffold increased periodically throughout 12 days compared with the other groups. Although the number of ADSCs on ε-PCL scaffold increased until the 6th day of the culture, the cell number began to decrease after day 6.. These results were associated with the decomposition of PCL scaffolds that occurs through catabolic reactions. This causes the release of lactic acid which makes toxic effect on the cells. Thus, these results showed that egg white scaffold increases and protects cell adhesion and cell viability more than ε-Polycaprolactone scaffold, thus it can be used as a scaffold in tissue engineering studies that involve stem cells.

PLGA-based microspheres containing ropivacaine and betamethasone for sciatic nerve block in mice

The aim of the present study was to develop Poly (lactic-co-glycolic acid) (PLGA)-based microspheres containing ropivacaine and betamethasone (RPC/BTM PLGA MS) by emulsion-solvent evaporation method. RPC/BTM PLGA MS were characterized by physical properties, such as morphology and particle size, and in vitro drug release. In addition, in vivo pharmacokinetics and pharmacodynamics of RPC/BTM PLGA MS were also investigated. The prepared RPC/BTM PLGA MS was suitable for local injection with a well-dispersed spherical shape, high stability, and high encapsulation efficiency. The mean diameter was 14.8 ± 1.2 µm and the polydispersity index (PDI) was 0.32 ± 0.04. In an in vitro study of drug release, it can be concluded that the RPC/BTM PLGA MS exhibited sustained and long-term release properties for 16 days. Furthermore, the result of an in vivo study indicated that the RPC/BTM PLGA MS had sustained release effect and the pharmacodynamics result showed that preparing RPC/BTM PLGA MS as microsphere preparation could not only extend the drug effect time but also prolong the duration of local anesthetics compared with the common RPC PLGA MS.

Hydrolyzable Poly(β-Thioether Ester Ketal) Thermosets via Acyclic Ketal Monomers

Hydrolytically degradable poly(β-thioether ester ketal) thermosets are synthesized via radical-mediated thiol-ene photopolymerization using three novel dialkene acyclic ketal monomers and a mercaptopropionate based tetrafunctional thiol. For all thermoset compositions investigated, degradation behavior is highly tunable based on the structure of the incorporated ketal and pH. Complete degradation of the thermosets is observed upon exposure to acidic and neutral pH, and under high humidity conditions. Polymer networks comprised of crosslink junctions based on acyclic dimethyl ketals degrade the quickest, whereas networks containing acyclic cyclohexyl ketals undergo hydrolytic degradation on a longer timescale. Thermomechanical analysis revealed low glass transition temperatures and moduli typical of thioether-based thermosets. This article is protected by copyright. All rights reserved.

Poly(Lactic Acid)-Based Microparticles for Drug Delivery Applications: An Overview of Recent Advances

The sustained release of pharmaceutical substances remains the most convenient way of drug delivery. Hence, a great variety of reports can be traced in the open literature associated with drug delivery systems (DDS). Specifically, the use of microparticle systems has received special attention during the past two decades. Polymeric microparticles (MPs) are acknowledged as very prevalent carriers toward an enhanced bio-distribution and bioavailability of both hydrophilic and lipophilic drug substances. Poly(lactic acid) (PLA), poly(lactic-co-glycolic acid) (PLGA), and their copolymers are among the most frequently used biodegradable polymers for encapsulated drugs. This review describes the current state-of-the-art research in the study of poly(lactic acid)/poly(lactic-co-glycolic acid) microparticles and PLA-copolymers with other aliphatic acids as drug delivery devices for increasing the efficiency of drug delivery, enhancing the release profile, and drug targeting of active pharmaceutical ingredients (API). Potential advances in generics and the constant discovery of therapeutic peptides will hopefully promote the success of microsphere technology.

Synthesis and properties of ABA-triblock copolymers from polyester A-blocks and easily degradable polyacetal B-blocks

Novel, degradable amphiphilic ABA triblock copolymers with a polyacetal chain as the hydrophilic internal block and polyesters as external hydrophobic segments were designed and prepared for the first time in a controlled manner.

Shape Memory Materials from Rubbers

Smart materials are much discussed in the current research scenario. The shape memory effect is one of the most fascinating occurrences in smart materials, both in terms of the phenomenon and its applications. Many metal alloys and polymers exhibit the shape memory effect (SME). Shape memory properties of elastomers, such as rubbers, polyurethanes, and other elastomers, are discussed in depth in this paper. The theory, factors impacting, and key uses of SME elastomers are all covered in this article. SME has been observed in a variety of elastomers and composites. Shape fixity and recovery rate are normally analysed through thermomechanical cycle studies to understand the effectiveness of SMEs. Polymer properties such as chain length, and the inclusion of fillers, such as clays, nanoparticles, and second phase polymers, will have a direct influence on the shape memory effect. The article discusses these aspects in a simple and concise manner.

Trends of Chitosan Based Delivery Systems in Neuroregeneration and Functional Recovery in Spinal Cord Injuries

Spinal cord injury (SCI) is one of the most complicated nervous system injuries with challenging treatment and recovery. Regenerative biomaterials such as chitosan are being reported for their wide use in filling the cavities, deliver curative drugs, and also provide adsorption sites for transplanted stem cells. Biomaterial scaffolds utilizing chitosan have shown certain therapeutic effects on spinal cord injury repair with some limitations. Chitosan-based delivery in stem cell transplantation is another strategy that has shown decent success. Stem cells can be directed to differentiate into neurons or glia in vitro. Stem cell-based therapy, biopolymer chitosan delivery strategies, and scaffold-based therapeutic strategies have been advancing as a combinatorial approach for spinal cord injury repair. In this review, we summarize the recent progress in the treatment strategies of SCI due to the use of bioactivity of chitosan-based drug delivery systems. An emphasis on the role of chitosan in neural regeneration has also been highlighted.

Thiol- and Disulfide-Based Stimulus-Responsive Soft Materials and Self-Assembling Systems

Properties and applications of synthetic thiol- and disulfide-based materials, principally polymers, are reviewed. Emphasis is placed on soft and self-assembling materials in which interconversion of the thiol and disulfide groups initiates stimulus-responses and/or self-healing for biomedical and non-biomedical applications.

Effects of reinforcement of sodium alginate functionalized halloysite clay nanotubes on thermo-mechanical properties and biocompatibility of poly (vinyl alcohol) nanocomposites

In the present work sodium alginate functionalized halloysite nanotubes (HNTs) reinforced poly (vinyl alcohol) nanocomposite films were prepared by solution casting technique. Sodium alginate surface functionalizing on the HNTs through hydrogen bonding was confirmed by spectroscopic and morphological analysis. The functionalized HNTs were successfully incorporated into the PVA matrix. Further, the films were characterized by using FTIR, TGA, XRD, SEM, AFM, UTM, WCA and swelling ratio analysis. The obtained results indicated improved physico-thermal properties, and uniform distribution of nanotubes in the matrix and roughness of the surface compared with the pristine PVA films. After inclusion of functionalized nanotubes causes enhancement of tensile strength as well as young's modulus of the nanocomposite films. Water contact angle measurement was carried out to know the hydrophilic or hydrophobic nature of the films and results were correlated with swelling ratio analysis. Furthermore, the films were analyzed for in-vitro biocompatibility studies. In -vitro enzymatic degradation was carried out in PBS media and cellular behaviour studies were analyzed using NIH3T3 cell lines. The results showed enhancement in the enzymatic degradation, proliferation, adhesion activity compared to that of pristine PVA films. In extension, nanocomposite films were subjected to hemocompatibility studies using human erythrocyte. The results revealed that nanocomposite films were biocompatible and hemocompatible. The fabricated films can be used in biomedical application.

Cooperative Heterometallic Catalysts for Lactide Ring-Opening Polymerization: Combining Aluminum with Divalent Metals

While homometallic (salen)Al catalysts display excellent performance in lactide ring-opening polymerization (ROP), heterometallic (salen)Al complexes have yet to be reported. Herein, we describe four heterobimetallic (salen)Al catalysts and show that the choice of the heterometal is key. Cooperative Al/Mg and Al/Zn combinations improved the catalyst activity by a factor of up to 11 compared to the mono-Al analogue, whereas the mono-Mg and mono-Zn analogues were completely inactive. In contrast, Al/Li and Al/Ca heterocombinations stunted the polymerization rate. Kinetic and computational studies suggest that Al/Mg and Al/Zn cooperativity arises from the close intermetallic proximity facilitating chloride bridging (thus enhancing initiation), which promotes a rigid square pyramidal geometry around the Al center and further increases the available monomer coordination sites. This work also translates the use of ab initio molecular dynamics calculations to ROP, introducing a useful method of investigating catalyst flexibility and revealing that ligand strain and molecular rigidity can enhance heterometallic catalyst performance.

Injectable RANKL sustained release formulations to accelerate orthodontic tooth movement

BACKGROUND

Accelerating orthodontic tooth movement (OTM) through biologically effective methods, such as increasing osteoclast-mediated alveolar resorption, could effectively shorten treatment time.

OBJECTIVE

To evaluate an injectable formulation containing receptor activator of nuclear factor kappa-B ligand (RANKL) on the OTM.

MATERIALS AND METHODS

We fabricated a RANKL formulation from 100 µl of 100 µg/ml RANKL adsorbed on 10 mg of poly(lactic acid-co-glycolic acid) microspheres embedded in a 10 wt% aqueous hydroxyethyl cellulose carrier gel. We characterized these formulations for the rate of RANKL release, and then tested for bioactivity using in vitro cell culture. In vivo OTM studies were conducted using 15 week old male Wistar rats for 14 days. We injected the RANKL formulations palatal to the left maxillary first molar and accomplished OTM with a nickel-titanium (NiTi) coil spring applying 5-8 g force. Control groups involved the application of NiTi coil spring with and without placebo formulation. The outcome measure included the distance of tooth movement, bone volume fraction, tissue density, and root volume determined with micro-computed tomography. We determined the amount of osteoclast activity using tartrate-resistant acid phosphatase (TRAP) staining.

RESULTS

These formulations were able to sustain the release of RANKL for more than 30 days, and the released RANKL showed a positive effect on mice osteoclast precursor cells (RAW 264.7). Reported injectable RANKL formulations were effective in accelerating OTM compared with other control groups, with 129.2 per cent more tooth movement than no formulation and 71.8 per cent more than placebo formulation, corresponding with a significant increase in the amount of TRAP activity. We did not observe any significant differences in root resorption between the groups.

CONCLUSION

Our study shows a significant increase in OTM with injectable formulations containing RANKL.

A novel biodegradable external stent regulates vein graft remodeling via the Hippo-YAP and mTOR signaling pathways

Coronary artery bypass graft (CABG) has been confirmed to effectively improve the prognosis of coronary artery disease, which is a major public health concern worldwide. As the most frequently used conduits in CABG, saphenous vein grafts have the disadvantage of being susceptible to restenosis due to intimal hyperplasia. To meet the urgent clinical demand, adopting external stents (eStents) and illuminating the potential mechanisms underlying their function are important for preventing vein graft failure. Here, using 4-axis printing technology, we fabricated a novel biodegradable and flexible braided eStent, which exerts excellent inhibitory effect on intimal hyperplasia. The stented grafts downregulate Yes-associated protein (YAP), indicating that the eStent regulates vein graft remodeling via the Hippo-YAP signaling pathway. Further, as a drug-delivery vehicle, a rapamycin (RM)-coated eStent was designed to amplify the inhibitory effect of eStent on intimal hyperplasia through the synergistic effects of the Hippo and mammalian target of rapamycin (mTOR) signaling pathways. Overall, this study uncovers the underlying mechanisms of eStent function and identifies a new therapeutic target for the prevention of vein graft restenosis.

Copolymer Composition and Nanoparticle Configuration Enhance in vitro Drug Release Behavior of Poorly Water-soluble Progesterone for Oral Formulations

HYPOTHESIS

Developing oral formulations to enable effective release of poorly water-soluble drugs like progesterone is a major challenge in pharmaceutics. Coaxial electrospray can generate drug-loaded nanoparticles of strategic compositions and configurations to enhance physiological dissolution and bioavailability of poorly water-soluble drug progesterone.

EXPERIMENTS

Six formulations comprising nanoparticles encapsulating progesterone in different poly(lactide-co-glycolide) (PLGA) matrix configurations and compositions were fabricated and characterized in terms of morphology, molecular crystallinity, drug encapsulation efficiency and release behavior.

FINDINGS

A protocol of fabrication conditions to achieve 100% drug encapsulation efficiency in nanoparticles was developed. Scanning electron microscopy shows smooth and spherical morphology of 472.1±54.8 to 588.0±92.1 nm in diameter. Multiphoton Airyscan super-resolution confocal microscopy revealed core-shell nanoparticle configuration. Fourier transform infrared spectroscopy confirmed presence of PLGA and progesterone in all formulations. Diffractometry indicated amorphous state of the encapsulated drug. UV-vis spectroscopy showed drug release increased with hydrophilic copolymer glycolide ratio while core-shell formulations with progesterone co-dissolved in PLGA core exhibited enhanced release over five hours at 79.9±1.4% and 70.7±3.5% for LA:GA 50:50 and 75:25 in comparison with pure progesterone without polymer matrix in the core at 67.0±1.7% and 57.5±2.8%, respectively. Computational modeling showed good agreement with the experimental drug release behavior in vitro.

Sterilization process of polyester based anticancer-drug delivery systems

Recently, growing interest in biodegradable polyesters as drug carriers in the development of innovative anticancer drug delivery systems (DDSs) has been observed. These compounds are thermally unstable, and are therefore, particularly demanding due to the limited number of available sterilization techniques. Furthermore, the DDSs sterilization process is often limited to aseptic filtration. Ensuring aseptic production is very demanding and costly, and it is therefore necessary to work on the application of new sterilization methods. In view of this, this review presents the current state of knowledge regarding the radiation sterilization process of some anticancer drugs as well biodegradable polyester carriers (such as polylactide, polyglycolide, poly(ε-caprolactone), poly(trimethylene carbonate) and co- or terpolymers of lactide, glycolide, ε-caprolactone and trimethylene carbonate). The structural changes in anticancer DDSs under the influence of ionizing radiation and the potential degradation mechanisms of both, polyester carriers and cytostatics during the sterilization process of ionizing radiation as well as their effects on the microstructure and properties of DDSs have been discussed in this paper.

Synthesis of Biodegradable Polymers: A Review on the Use of Schiff-Base Metal Complexes as Catalysts for the Ring Opening Polymerization (ROP) of Cyclic Esters

This review describes the recent advances (from 2008 onwards) in the use of Schiff-base metal complexes as catalysts for the ring opening polymerization (ROP) of cyclic esters. The synthesis and structure of the metal complexes, as well as all aspects concerning the polymerization process and the characteristics of the polymers formed, will be discussed.

Ring-Opening Copolymerizaton of Cyclohexene Oxide and Succinic Anhydride by Zinc and Magnesium Schiff-Base Complexes Containing Alkoxy Side Arms

The ring-opening copolymerization (ROCOP) of epoxides and cyclic anhydrides is a promising method for the synthesis of new polyesters with various polymer properties. Among previously reported metal catalysts for ROCOP, the Schiff-base complexes have gained significant attention because of their ease of synthesis and modification. In this work, zinc and magnesium complexes containing Schiff-base ligands with different alkoxy side arms [-(CH₂)₂O- and -(CH₂)₃O-] were synthesized and shown to have a cubane metal core by X-ray crystal structures. All complexes were studied in the ROCOP of cyclohexene oxide (CHO) and succinic anhydride (SA) in toluene at 110 °C. The zinc complex having a shorter side arm is the most active catalyst for copolymerization, giving poly(CHO-alt-SA) with narrow dispersity and negligible ether linkage. On the other hand, magnesium complexes were not active because of the formation of stable carboxylate species. The detailed analysis of polyester obtained from zinc complexes unexpectedly revealed three different types of polymer structures occurring at different polymerization times. Cyclic polymer was generated at the beginning by intramolecular transesterification of the alkoxy side arm, giving a low-molecular-weight polyester. At higher conversion, cyclization diminished, giving just a linear polyester but with minor competitive formation of higher-molecular-weight polyester having cyclohexanediol as an end group. On the basis of a thorough understanding of the polymerization mechanism, the desired cyclic poly(CHO-alt-SA) was successfully synthesized using a low monomer/catalyst ratio.

Wireless implantable and biodegradable sensors for postsurgery monitoring: current status and future perspectives

In in vivo postsurgery monitoring, the use of wireless biodegradable implantable sensors has gained and is gaining a lot of interest, particularly in cases of monitoring for a short period of time. The employment of biodegradable materials allows the circumvention of secondary surgery for device removal. Additionally, the use of wireless communication for data elaboration avoids the need for transcutaneous wires. As such, it is possible to prevent possible inflammation and infections associated with long-term implants which are not wireless. It is expected that microfabricated biodegradable sensors will have a strong impact in acute or transient biomedical applications. However, the design of such high-performing electronic systems, both fully biodegradable and wireless, is very complex, particularly at small scales. The associated technologies are still in their infancy and should be more deeply and extensively investigated in animal models and, successively, in humans, before being clinically implemented. In this context, the present review aims to provide a complete overview of wireless biodegradable implantable sensors, covering the vital signs to be monitored, the wireless technologies involved, and the biodegradable materials used for the production of the devices, as well as designed devices and their applications. In particular, both their advantages and drawbacks are highlighted, and the key challenges faced, mainly associated with fabrication techniques, and control over degradation kinetics and biocompatibility of the device, are reported and discussed.

Recent Advance in Polymer Based Microspheric Systems for Controlled Protein and Peptide Delivery

Sustained-release systems made by biodegradable polymers for protein and peptide drug delivery have received considerable attention by academic researchers and major pharmaceutical companies around the world. Various types of biodegradable materials, including natural and synthetic polymers, have been applied to form protein and peptide drug carriers. Among these material candidates, poly lactic acid (PLA) and poly lactic-co-glycolic acid (PLGA) are the most commonly used biodegradable materials in the development of protein and peptide microspheres. In addition, many microsphere preparation technologies, including spray drying, coacervation, multiple emulsion solvent evaporation method and microporous membrane emulsification have been developed for microspheres preparation. In this review, we particularly summarize and briefly introduce the materials and methods that are used to fabricate microspheres as protein delivery systems. The existing opportunities and challenges for successful protein delivery are also discussed.

Encapsulation and release of doxycycline from electrospray-generated PLGA microspheres: Effect of polymer end groups

The aim of this study was to investigate the influence of end group of poly(lactic-co-glycolic acid) (PLGA) on the drug loading and release behavior of electrospray-generated PLGA microspheres. To this end, doxycycline hyclate (DOX) was selected as a model drug, and PLGA (molecular weight: 17 and 44 kDa) with either an acid or ester end group were electrosprayed with DOX. The processing parameters were optimized to obtain microspheres comparable in size. Drug loading efficiency and release profile were determined by the high-performance liquid chromatography-ultraviolet detection (HPLC-UV) method. PLGA polymers or drug-loaded microspheres were characterized before and after exposure to phosphate buffer saline at 37 °C regarding the wettability of polymers, pH changes of the buffer, molecular weight of PLGA and morphology of the microspheres. The acid end group of PLGA microspheres brought about lower encapsulation efficiency and faster DOX release rate in our study, indicating that different hydrophilicity of polymer and degradation speed were the main reasons causing a difference in encapsulation efficiency and release profile. In addition, DOX released from the PLGA microspheres was active by showing antibacterial effects against Porphyromonas gingivalis as measured using a zone of inhibition test, and varying the end groups showed no impact on the antibacterial efficacy. This study demonstrated that the end group of PLGA can be used as a new tool to regulate drug encapsulation efficiency and release rate to meet different clinical drug delivery requirements.

Hydrolytically degradable poly(β-thioether ester ketal) thermosets via radical-mediated thiol–ene photopolymerization

Poly(β-thioether ester ketal) networks are reported that undergo complete degradation with tuneable degradation profiles under acid and/or basic conditions.

Electrospraying Electrospun Nanofiber Segments into Injectable Microspheres for Potential Cell Delivery

Nanofiber microspheres have attracted a lot of attention for biomedical applications because of their injectable and biomimetic properties. Herein, we report for the first time a new method for fabrication of nanofiber microspheres by combining electrospinning and electrospraying and explore their potential applications for cell therapy. Electrospraying of aqueous dispersions of electrospun nanofiber segments with desired length obtained by either cryocutting or homogenization into liquid nitrogen followed by freeze-drying and thermal treatment can form nanofiber microspheres. The microsphere size can be controlled by varying the applied voltage during the electrospray process. A variety of morphologies were achieved including solid, nanofiber, porous and nanofiber microspheres, and hollow nanofiber microspheres. Furthermore, a broad range of polymer and inorganic bioactive glass nanofiber-based nanofiber microspheres could be fabricated by electrospraying of their short nanofiber dispersions, indicating a comprehensive applicability of this method. A higher cell carrier efficiency of nanofiber microspheres as compared to solid microspheres was demonstrated with rat bone marrow-derived mesenchymal stem cells, along with the formation of microtissue-like structures in situ, when injected into microchannel devices. Also, mouse embryonic stem cells underwent neural differentiation on the nanofiber microspheres, indicated by positive staining of β-III-tubulin and neurite outgrowth. Taken together, we developed a new method for generating nanofiber microspheres that are injectable and have improved viability and maintenance of stem cells for potential application in cell therapy.

Preparation and in vitro characterization of retinoic acid-loaded poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) micelles

In order to achieve the controlled release of all-trans-retinoic acid (ATRA), poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL) copolymer with average molecular weight of 5.34 kDa was synthesized. The nanosized micelles were prepared from copolymer by nano-precipitation method. Critical association concentration (CAC) of micelles was measured by fluorimetry and results indicated low CAC value of micelles (1.9 × 10^-3 g/L). ATRA was encapsulated in the core of micelles using different ratios of drug to copolymer. In the case of 10% drug to polymer ratio, more than 80% of the drug was released within 3 days, whereas for ratio of 2% more than 90% of the drug was released within 3 h. The cytotoxic study performed by MTT assay showed that H1299 survival percent decreased significantly (P ≤ 0.05) after exposure to drug-loaded micelles, while no proliferation inhibition effect was observed by either free ATRA or blank PCL-PEG-PCL micelles.

Preparation and evaluation of cefquinome-loaded gelatin microspheres and the pharmacokinetics in pigs

Cefquinome (CEF) is widely used for veterinary clinical applications because of its broad spectrum and high efficiency. However, frequent administrations are required due to its short elimination half-life. In this study, cefquinome sulfate gelatin microspheres (CEF-GMS) were prepared as a sustained-release formulation using emulsion chemical cross-linking technique. Physical properties, stability, sustained-release property in vitro, and pharmacokinetics in pigs were assessed. The morphology of CEF-GMS showed a good sphericity with porous structure on the surface, and the mean diameter was 8.80 ± 0.78 μm, with 90.60 ± 3.98% of the total in the range of 5-20 μm. There were no significant changes of all estimated indexes in the stability tests. In vitro drug release study showed that the release of CEF from CEF-GMS was much slower than that from crude CEF in a release medium. Pharmacokinetic characteristics were evaluated following intramuscular administration of CEF-GMS or Cefquinome sulfate injection (CEF-Inj) in pigs at a dosage of 4 mg CEF/kg body weight. The plasma drug concentration-time data of CEF-GMS and CEF-Inj were both best fitted by two-compartment models with first-order absorption, and the elimination half-life of CEF-GMS was almost 10 times that of CEF-Inj. Overall, CEF-GMS might be used as a sustained-release formulation of CEF for veterinary clinical applications.

Poly(lactic acid)-based particulate systems are promising tools for immune modulation

Poly(lactic acid) (PLA) is one of the most successful and versatile polymers explored for controlled delivery of bioactive molecules. Its attractive properties of biodegradability and biocompatibility in vivo have contributed in a meaningful way to the approval of different products by the FDA and EMA for a wide range of biomedical and pharmaceutical applications, in the past two decades. This polymer has been widely used for the preparation of particles as delivery systems of several therapeutic molecules, including vaccines. These PLA vaccine carriers have shown to induce a sustained and targeted release of different bacterial, viral and tumor-associated antigens and adjuvants in vivo, triggering distinct immune responses. The present review intends to highlight and discuss the major advantages of PLA as a promising polymer for the development of potent vaccine delivery systems against pathogens and cancer. It aims to provide a critical discussion based on preclinical data to better understand the major effect of PLA-based carrier properties on their interaction with immune cells and thus their role in the modulation of host immunity.

STATEMENT OF SIGNIFICANCE

During the last decades, vaccination has had a great impact on global health with the control of many severe diseases. Polymeric nanosystems have emerged as promising strategies to stabilize vaccine antigens, promoting their controlled release to phagocytic cells, thus avoiding the need for multiple administrations. One of the most promising polymers are the aliphatic polyesters, which include the poly(lactic acid). This is a highly versatile biodegradable and biocompatible polymer. Products containing this polymer have already been approved for all food and some biomedical applications. Despite all favorable characteristics presented above, PLA has been less intensively discussed than other polymers, such as its copolymer PLGA, including regarding its application in vaccination and particularly in tumor immunotherapy. The present review discusses the major advantages of poly(lactic acid) for the development of potent vaccine delivery systems, providing a critical view on the main properties that determine their effect on the modulation of immune cells.

Preparation of a reproducible long-acting formulation of risperidone-loaded PLGA microspheres using microfluidic method

The aim of the present study is to prepare risperidone-loaded poly lactic-co-glycolic acid (PLGA) microspheres within microfluidic system and to achieve a formulation with uniform size and monotonic and reproducible release profile. In comparison to batch method, T-junction and serpentine chips were utilized and optimizing study was carried out at different processing parameters (e.g. PLGA and surfactant concentration and flow rates ratio of outer to inner phase). The computational fluid dynamic (CFD) modeling was performed, and loading and release study were carried out. CFD simulation indicates that increasing the flow rate of aqueous phase cause to decrease the droplet size, while the change in size of microspheres did not follow a specific pattern in the experimental results. The most uniform microspheres and narrowest standard deviation (66.79 μm ± 3.32) were achieved using T-junction chip, 1% polyvinylalcohol, 1% PLGA and flow rates ratio of 20. The microfluidic-assisted microspheres were more uniform with narrower size distribution. The release of risperidone from microspheres produced by the microfluidic method was more reproducible and closer to zero-order kinetic model. The release profile of formulation with 2:1 drug-to-polymer ratio was the most favorable release, in which 41.85% release could be achieved during 24 days.

Redefining the functions of nanocapsule materials

Nanocapsules are key components in new technologies related to biomedicine and materials science. However, their long-term fate after use is still largely ignored. We discuss here a sustainable approach where the products of degradation of the nanoparticles play a significant role in their application because they are also functional molecules. The polymer shell of the nanocapsules is chemically engineered so that the degradation products formed upon chemical damage are useful after their normal use.

Thermostabilization of inactivated polio vaccine in PLGA-based microspheres for pulsatile release

Vaccines are a critical clinical tool in preventing illness and death due to infectious diseases and are regularly administered to children and adults across the globe. In order to obtain full protection from many vaccines, an individual needs to receive multiple doses over the course of months. However, vaccine administration in developing countries is limited by the difficulty in consistently delivering a second or third dose, and some vaccines, including the inactivated polio vaccine (IPV), must be injected more than once for efficacy. In addition, IPV does not remain stable over time at elevated temperatures, such as those it would encounter over time in the body if it were to be injected as a single-administration vaccine. In this manuscript, we describe microspheres composed of poly(lactic-co-glycolic acid) (PLGA) that can encapsulate IPV along with stabilizing excipients and release immunogenic IPV over the course of several weeks. Additionally, pH-sensitive, cationic dopants such as Eudragit E polymer caused clinically relevant amounts of stable IPV release upon degradation of the PLGA matrix. Specifically, IPV was released in two separate bursts, mimicking the delivery of two boluses approximately one month apart. In one of our top formulations, 1.4, 1.1, and 1.2 doses of the IPV serotype 1, 2, and 3, respectively, were released within the first few days from 50mg of particles. During the delayed, second burst, 0.5, 0.8, and 0.6 doses of each serotype, respectively, were released; thus, 50mg of these particles released approximately two clinical doses spaced a month apart. Immunization of rats with the leading microsphere formulation showed more robust and long-lasting humoral immune response compared to a single bolus injection and was statistically non-inferior from two bolus injections spaced 1 month apart. By minimizing the number of administrations of a vaccine, such as IPV, this technology can serve as a tool to aid in the eradication of polio and other infectious diseases for the improvement of global health.