Biodegradable microspheres for protein delivery

Effect of Poly-L-lysine Coating on Retinoic Acid-Loaded PLGA Microspheres in the Differentiation of Carcinoma Stem Cells into Neural Cells

In this study, PLGA microspheres were prepared using a water-in-oil-in-water emulsion/solvent evaporation technique. Some microspheres were coated with poly-L-lysine (an extracellular matrix (ECM) component), and then pluripotent P19 embryonic carcinoma cells were seeded on them. P19 cells attached onto the PLGA microspheres; subsequently, by adding retinoic acid (RA) to cell culture medium as a neurogenic inducer (RA was released from the microspheres), the cells differentiated into neural cells. Size and morphology of PLGA microspheres was characterized by scanning electron microscopy (SEM). Neurogenic differentiation was studied by immunofluorescent staining, real-time polymerase chain reaction (RT-PCR), and light microscopy. Histological assay showed that more cells attached onto microspheres coated with poly-L-lysine than the uncoated group. Immunofluoresent staining and RT-PCR analysis for β-Tubulin, Nestin and Pax6 genes indicated differentiation of P19 cells into neural cells on both coated and uncoated microspheres. It was found that a high surface area of microspheres improves cell attachment and expansion, which was significantly increased in those coated with poly-L-lysine. Finally, these results highlight the versatility of these sample scaffolds as a model system for nerve tissue engineering.

Tension-Activated Delivery of Small Molecules and Proteins from Superhydrophobic Composites

The fabrication and performance of mechanically responsive multilayer superhydrophobic composites are reported. The application of tensile strain triggers the release of small molecules and proteins from these composites, with different tensile strain magnitudes and coating thickness influencing agent release. These mechanoresponsive composites consist of an absorbent drug core surrounded by an electrosprayed superhydrophobic protective coating that limits drug release in the absence of tensile strain. Coating thickness and applied tensile strain control release of chemotherapeutic cisplatin and enzyme β-galactosidase, as measured by atomic absorption and UV-vis spectrophotometry, respectively, with preserved in vitro activity. Such mechanically responsive drug delivery devices, when coupled to existing dynamic mechanical forces in the body or integrated with mechanical medical devices, such as stents, will provide local controlled dosing.

Polydopamine Modified TiO2 Nanotube Arrays for Long-Term Controlled Elution of Bivalirudin and Improved Hemocompatibility

Sustained and controllable release characteristics are pivotal factors for novel drug delivery technologies. TiO₂ nanotube arrays prepared by self-ordering electrochemical anodization are attractive for the development of biomedical devices for local drug delivery applications. In this work, several layers of polydopamine (PDA) were deposited to functionalize TiO₂ nanotube arrays. The anticoagulant drug bivalirudin (BVLD) was used as a model drug. PDA extended the release period of BVLD and maintained a sustained release kinetic. Depending on the number of PDA layers, the release characteristics of BVLD improved, as there was a reduced burst release (from 45% to 11%) and extended overall release period from 40 days to more than 300 days in the case of 5 layers. Besides, the BVLD loaded 5-layer PDA coating maintained the high bioactivity of BVLD and effectively reduced the thrombosis formation by inhibition of the adhesion and denaturation of fibrinogen, platelets, and other blood components. Both in vitro and ex vivo blood evaluation results demonstrated that this coating significantly improved the hemocompatibility. These results confirmed the capability of PDA fitted TiO₂ nanotube systems to be applied for local drug delivery over an extended period with well retained bioactivity and predictable release kinetics.

Microspheres as intraocular therapeutic tools in chronic diseases of the optic nerve and retina

Pathologies affecting the optic nerve and the retina are one of the major causes of blindness. These diseases include age-related macular degeneration (AMD), diabetic retinopathy (DR) and glaucoma, among others. Also, there are genetic disorders that affect the retina causing visual impairment. The prevalence of neurodegenerative diseases of the posterior segment is increased as most of them are related with the elderly. Even with the access to different treatments, there are some challenges in managing patients suffering retinal diseases. One of them is the need for frequent interventions. Also, an unpredictable response to therapy has suggested that different pathways may be playing a role in the development of these diseases. The management of these pathologies requires the development of controlled drug delivery systems able to slow the progression of the disease without the need of frequent invasive interventions, typically related with endophthalmitis, retinal detachment, ocular hypertension, cataract, inflammation, and floaters, among other. Biodegradable microspheres are able to encapsulate low molecular weight substances and large molecules such as biotechnological products. Over the last years, a large variety of active substances has been encapsulated in microspheres with the intention of providing neuroprotection of the optic nerve and the retina. The purpose of the present review is to describe the use of microspheres in chronic neurodegenerative diseases affecting the retina and the optic nerve. The advantage of microencapsulation of low molecular weight drugs as well as therapeutic peptides and proteins to be used as neuroprotective strategy is discussed. Also, a new use of the microspheres in the development of animal models of neurodegeneration of the posterior segment is described.

Calcium-dependent protein kinases are potential targets for Toxoplasma gondii vaccine

Toxoplasma gondii belongs to the Apicomplexa phylum that caused a widespread zoonotic infection in wide range of intermediate hosts. Over one-third of the world's population are latently infected with T. gondii and carry it. The complex life cycle of T. gondii indicates the presence of a plurality of antigenic epitopes. During the recent years, continuous efforts of scientists have made precious advances to elucidate the different aspects of the cell and molecular biology of T. gondii. Despite of great progresses, the development of vaccine candidates for preventing of T. gondii infection in men and animals is still remains a challenge. The calcium-dependent protein kinases (CDPKs) belongs to the superfamily of kinases, which restricted to the apicomplexans, ciliates, and plants. It has been documented that they contribute several functions in the life cycle of T. gondii such as gliding motility, cell invasion, and egress as well as some other critical developmental processes. In current paper, we reviewed the recent progress concerning the development of CDPK-based vaccines against acute and chronic T. gondii.

Implications of designing a bromelain loaded enteric nanoformulation on its stability and anti-inflammatory potential upon oral administration

The objective of the present investigation was to develop an enteric nano-formulation of bromelain to improve its stability and anti-inflammatory potential. Bromelain loaded nanoparticles (Br-NPs) were developed using a Eudragit L 100 polymer by a double emulsion solvent evaporation method to obtain gastro-resistant properties. Br-NPs were characterized for particle size (248.89 ± 22.76 nm), zeta potential (-27.34 ± 2.17 mV), entrapment efficiency (85.42 ± 5.34%), surface morphology (spherical) and in vitro release profile. Infrared spectroscopy confirmed the entrapment of bromelain while thermal and pXRD analysis concomitantly corroborated the reduced crystallinity of bromelain in nanoparticles. Formulations showed gastro-resistant behavior at gastric pH and sustained bromelain release up to 10 h in phosphate buffer at pH 6.8 and followed Higuchi square root release kinetics. The optimized lyophilized formulation ensured 2 year shelf-life at room temperature. In vivo studies revealed significantly improved performance of entrapped bromelain in inhibiting carrageenan induced paw edema by mitigating leucocyte migration and release of nitric oxide, TNFα and IL-1β in paw compared to bromelain solution. In conclusion, enteric Br-NPs could be a viable drug delivery system for effective oral bromelain delivery in inflammatory conditions.

One-pot preparation of polymer microspheres with different porous structures to sequentially release bio-molecules for cutaneous regeneration

Herein, we reveal a double emulsion method combining the sol–gel method to prepare poly(lactic-co-glycolic acid) microspheres with different porous structures for sequential release of two types of biomolecules.

Growth Factor Delivery Systems for Tissue Engineering and Regenerative Medicine

Growth factors (GFs) are often a key component in tissue engineering and regenerative medicine approaches. In order to fully exploit the therapeutic potential of GFs, GF delivery vehicles have to meet a number of key design criteria such as providing localized delivery and mimicking the dynamic native GF expression levels and patterns. The use of biomaterials as delivery systems is the most successful strategy for controlled delivery and has been translated into different commercially available systems. However, the risk of side effects remains an issue, which is mainly attributed to insufficient control over the release profile. This book chapter reviews the current strategies, chemistries, materials and delivery vehicles employed to overcome the current limitations associated with GF therapies.

The morphologies and fluorescence quantum yields of perylene diimide dye-doped PS and PHVB microspheres

Aggregation and continuous π-stacking have been the major obstacles hindering the fluorescence (FL) quantum yield (Φ_F) of perylene diimide (PDI) derivatives in the condensed phase. To prepare polymer microspheres with nearly unity Φ_F, in this work a POSS functionalized PDI derivative, POSS–PDI–POSS (PPP), was applied as the red fluorophore of poly(3-hydroxylbutyrate-co-3-hydroxyvalerate) (PHBV) and polystyrene (PS) microspheres. The electrosprayed PPP/PHBV and PPP/PS microspheres have unique hollow structures. Moreover, they show bright red FL under a fluorescence microscope. A photophysical study of the microspheres indicates a significant role of the polymer matrix in disrupting the aggregation state and the Φ_F of the embedded PPP fluorophore. Both the PPP/PHBV and the PPP/PS microspheres show higher Φ_F than most PDI materials in the condensed phase. The PPP/PHBV microspheres show Φ_F of 28%, whereas the PPP/PS microspheres give nearly unity Φ_F.

A POSS functionalized perylene diimide (PDI) derivative, PPP, is applied to polymer microspheres as a red fluorophore. Hollow PPP/polystyrene microspheres show a fluorescence quantum yield (Φ_F) of nearly unity.

Effect of surfactant on Pseudomonas aeruginosa colonization of polymer microparticles and flat films

Micro- and nanoparticles are of great interest because of their potential for trafficking into the body for applications such as low-fouling coatings on medical devices, drug delivery in pharmaceutics and cell carriers in regenerative medicine strategies. Particle production often relies on the use of surfactants to promote stable droplet formation. However, the presence of residual surfactant has been shown to complicate the surface chemistry and resultant properties. When forming particles from polymerizable monomer droplets, these polymeric surfactant chains can become physically entangled in the particle surface. Due to the key role of the outermost layers of the surface in biomaterial interactions, the surface chemistry and its influence on cells needs to be characterized. This is the first study to assess surfactant retention on microfluidic produced particles and its effect on bacterial attachment; surfactant contaminated microparticles are compared with flat films which are surfactant-free. Polymeric microparticles with an average diameter of 76 ± 1.7 μm were produced by using a T-junction microfluidic system to form monomer droplets which were subsequently photopolymerized. Acrylate based monomer solutions were found to require 2 wt% PVA to stabilize droplet formation. ToF-SIMS was employed to assess the surface chemistry revealing the presence of PVA in a discontinuous layer on the surface of microparticles which was reduced but not removed by solvent washing. The effect of PVA on bacterial (Pseudomonas aeruginosa) attachment was quantified and showed reduction as a function of the amount of PVA retained at the surface. The insights gained in this study help define the structure–function relationships of the particulate biomaterial architecture, supporting materials design with biofilm control.

The attachment of Pseudomonas aeruginosa on microfluidic produced particles was shown to reduce as a function of PVA concentration retained at the surface, enabling novel structure–function relationships of biomaterial architecture.

Modulating the release of proteins from a loaded carrier of alginate/gelatin porous spheres immersed in different solutions

BACKGROUND

A biodegradable porous particle for the controlled biofactor delivery which assembly of pores in scaffolds can improve the permeation and diffusion of drugs or growth factors.

OBJECTIVE

Porous-spheres in millimeter scale were prepared by mixing sodium alginate and gelatin interpenetrating networks with cross-linkers; interconnected open pores were fabricated through solvent casting and particulate leaching.

METHODS

Morphological characteristics, degradation, and bovine serum albumin (BSA) release rates of the porous-spheres immersed in three different solutions, namely, deionized distilled water, simulated body fluid (SBF), and phosphate-buffered saline (PBS), were detected.

RESULTS

Porous-spheres with a large amount of gelatin exhibited an increase in water absorption rates without affecting scaffold strength and no cytotoxicity was elicited. Highly interconnected pores with a diameter of 100-200 µm were uniformly distributed in scaffolds. The weight loss in PBS was faster than that in other solutions; the highest release rate of BSA in SBF was observed for 2 h. The release rates also exhibited linear patterns from 2 h to 24 h in all of the groups.

CONCLUSIONS

After 1 d of immersion in solutions, BSA release rates in scaffolds logarithmically decreased for 14 d. The degradation of porous-spheres also showed an inverse pattern.

In vivo and in vitro sustained release of ranibizumab from a nanoporous thin-film device

Current administration of ranibizumab and other therapeutic macromolecules to the vitreous and retina carries ocular risks, a high patient treatment burden, and compliance barriers that can lead to suboptimal treatment. Here we introduce a device that produces sustained release of ranibizumab in the vitreous cavity over the course of several months. Composed of twin nanoporous polymer thin films surrounding a ranibizumab reservoir, these devices provide release of ranibizumab over 16 weeks in vitro and 12 weeks in vivo, without exhausting the initial drug payload. Following implantation in vivo, devices were well-tolerated and showed no sign of immune response. This platform presents a potential solution to the challenge of delivering protein therapeutics to the vitreous and retina for sustained periods of time.

Recent advances in the use of nanoparticles for allergen-specific immunotherapy

The number of patients suffering from allergic asthma and rhinoconjunctivitis has increased dramatically within the last decades. Allergen-specific immunotherapy (AIT) is the only available cause-oriented therapy so far. AIT reduces symptoms, but has also a disease-modifying effect. Disadvantages are a long-lasting procedure, and in a few cases potential systemic adverse reactions. Encapsulation of allergens or DNA vaccines into nanostructures may provide advantages compared to the conventional AIT with noncapsulated allergen extracts: The protein/DNA molecule can be protected from degradation, higher local concentrations and targeted delivery to the site of action appear possible, and most importantly, recognition of encapsulated allergen by the immune system, especially by IgE antibodies, is prevented. AIT with nanoparticles (NPs) may offer a safer and potentially more efficient way of treatment for allergic diseases. In this review, we summarize the use of biodegradable NPs consisting of synthetic or natural polymers, liposomes, and virus-like particles as well as nonbiodegradable NPs like dendrimers, and carbon- or metal-based NPs for AIT. More or less successful applications of these NPs in prophylactic as well as therapeutic vaccination approaches in rodents or other animals as well as first human clinical trials are discussed in detail.

Sponge like microparticles for drug delivery and cosmeto-textile use: Formulation and human skin penetration

This unique work is targeted to achieve three main goals: i) to enhance the aqueous solubility of three specifically selected hydrophobic active agents, ii) to prepare such polymeric biodegradable microparticles which can encapsulate actives-cyclodextrin complexes and iii) to functionalize a polyamide base textile with active loaded microparticles and active-cyclodextrin loaded microparticles. To achieve this objective, biodegradable cationic microparticles were prepared via double emulsion solvent evaporation process and were loaded with hydroxypropyl-beta-cyclodextrin based complexes of Indomethacin, α-tocopheroland Lauryl Isoquinolinium Bromide during the formulation process. Inclusion complex based particles were evaluated for their morphology, size distribution, zeta potential, skin penetration aptitude and adsorption onto a selected textile. It was observed that active-cyclodextrin complex encapsulation do not affect the morphology, size and zeta potential of the microparticles as well as adsorption of the microparticles onto textile remains unaltered. However such active-cyclodextrin complex encapsulated particles provided the enhancement in the aqueous solubility of hydrophobic agents and also provided prolonged release formulations.

An Affordable Microsphere-Based Device for Visual Assessment of Water Quality

This work developed a prototype of an affordable, long-term water quality detection device that provides a visual readout upon detecting bacterial contamination. This device prototype consists of: (1) enzyme-releasing microspheres that lyse bacteria present in a sample, (2) microspheres that release probes that bind the DNA of the lysed bacteria, and (3) a detector region consisting of gold nanoparticles. The probes bind bacterial DNA, forming complexes. These complexes induce aggregation of the gold nanoparticles located in the detector region. The nanoparticle aggregation process causes a red to blue color change, providing a visual indicator of contamination being detected. Our group fabricated and characterized microspheres made of poly (ε-caprolactone) that released lysozyme (an enzyme that degrades bacterial cell walls) and hairpin DNA probes that bind to regions of the Escherichiacoli genome over a 28-day time course. The released lysozyme retained its ability to lyse bacteria. We then showed that combining these components with gold nanoparticles followed by exposure to an E. coli-contaminated water sample (concentrations tested-10⁶ and 10⁸ cells/mL) resulted in a dramatic red to blue color change. Overall, this device represents a novel low-cost system for long term detection of bacteria in a water supply and other applications.

In vivo comparison of jellyfish and bovine collagen sponges as prototype medical devices

Jellyfish have emerged as a source of next generation collagen that is an attractive alternative to existing sources, such as bovine and porcine, due to a plentiful supply and providing a safer source through lack of bovine spongiform encephalopathy (BSE) transmission risk and potential viral vectors, both of which could be transmitted to humans. Here we compare collagen implantable sponges derived for the first time from the Rhizostoma pulmo jellyfish. A further novelty for the research was that there was a comparison for sponges that were either uncrosslinked or crosslinked using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), and an assessment on how this affected resorption, as well as their biocompatibility compared to bovine type I collagen sponges. The scaffolds were prepared and examined using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) and scanning electron microscopy (SEM). The samples were implanted in adult male Wistar rats for in vivo experimentation. Both crosslinked and uncrosslinked jellyfish collagen sponges showed a significant reduction in histopathology scores over the course of the study, whereas the bovine collagen sponge scores were not significantly reduced. Both jellyfish collagen sponges and the bovine sponge were tolerated well by the hosts, and a recovery was visible in all samples, suggesting that R. pulmo jellyfish-derived collagen could offer compelling biocompatibility with wound healing applications. We also demonstrate that noncrosslinked samples could be safer with better resorption times than crosslinked samples. © 2017 The Authors Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1524-1533, 2018.

Controlled release of GAG-binding enhanced transduction (GET) peptides for sustained and highly efficient intracellular delivery

Controlled release systems for therapeutic molecules are vital to allow the sustained local delivery of their activities which direct cell behaviour and enable novel regenerative strategies. Direct programming of cells using exogenously delivered transcription factors can by-pass growth factor signalling but there is still a requirement to deliver such activity spatio-temporally. We previously developed a technology termed GAG-binding enhanced transduction (GET) to efficiently deliver a variety of cargoes intracellularly, using GAG-binding domains which promote cell targeting, and cell penetrating peptides (CPPs) which allow cell entry. Herein we demonstrate that GET system can be used in controlled release systems to mediate sustained intracellular transduction over one week. We assessed the stability and activity of GET peptides in poly(dl-lactic acid-co-glycolic acid) (PLGA) microparticles (MPs) prepared using a S/O/W double emulsion method. Efficient encapsulation (∼65%) and tailored protein release profiles could be achieved, however intracellular transduction was significantly inhibited post-release. To retain GET peptide activity we optimized a strategy of co-encapsulation of l-Histidine, which may form a complex with the PLGA degradation products under acidic conditions. Simulations of the polymer microclimate showed that hydrolytic acidic PLGA degradation products directly inhibited GET peptide transduction activity, and use of l-Histidine significantly enhanced released protein delivery. The ability to control the intracellular transduction of functional proteins into cells will facilitate new localized delivery methods and allow approaches to direct cellular behaviour for many regenerative medicine applications.

STATEMENT OF SIGNIFICANCE

The goal for regenerative medicine is to restore functional biological tissue by controlling and augmenting cellular behaviour. Either Transcription (TFs) or growth factors (GFs) can be presented to cells in spatio-temporal gradients for programming cell fate and gene expression. Here, we have created a sustained and controlled release system for GET (Glycosaminoglycan-enhanced transducing)-tagged proteins using S/O/W PLGA microparticle fabrication. We demonstrated that PLGA and its acidic degradants inhibit GET-mediated transduction, which can be overcome by using pH-activated l-Histidine. l-Histidine inhibits the electrostatic interaction of GET/PLGA and allows enhanced intracellular transduction. GET could provide a powerful tool to program cell behaviour either in gradients or with sustained delivery. We believe that our controlled release systems will allow application of GET for tissue regeneration directly by TF cellular programming.

Long-Acting Release Formulation of Exendin-4 Based on Biomimetic Mineralization for Type 2 Diabetes Therapy

Exendin-4 has been clinically exploited for treating type 2 diabetes, but the short circulation half-life and multiple daily injections limit its widespread application with respect to poor patient compliance, low efficacy, and high treatment cost. In this study, a potent long-acting release system based on biomimetic mineralization was constructed for biocompatible and sustained exendin-4 delivery. Similar to natural biomineralization, exendin-4 can be mineralized to form nanosized mineral solids by means of the reaction between acidic amino acid residues and calcium ions in a supersaturated environment with negligible influence on peptide bioactivity. Mineralized exendin-4 particles may be spontaneously absorbed by a living body under physiologically supersaturated conditions, resulting in gradual dissociation and sustained drug release. In such a way, the glucose level of diabetic mice may be effectively controlled for a long period of time by mineralized exendin-4 without obvious side effects. We believe this biomimetic formulation can serve as a promising candidate for future clinical applications for type 2 diabetes therapies.

Design of electrohydrodynamic sprayed polyethylene glycol hydrogel microspheres for cell encapsulation

Electrohydrodynamic spraying (EHS) has recently gained popularity for microencapsulation of cells for applications in cell delivery and tissue engineering. Some of the polymers compatible with EHS are alginate, chitosan, and other similar natural polymers, which are subject to ionotropic or physical gelation. It is desirable to further extend the use of the EHS technique beyond such polymers for wider biofabrication applications. Here, building upon our previous work of making PEG microspheres via EHS, we utilized the principles of EHS to fabricate cell-laden polyethylene glycol (PEG) hydrogel microspheres. The gelation of PEG hydrogel microspheres was achieved by forming covalent crosslinks between multiarm PEG acrylate and dithiol crosslinkers via Michael-type addition. We conducted a detailed investigation of the critical parameters of EHS, such as the applied voltage, inner needle diameter (i.d. needle), and flow rate, to obtain PEG microspheres with high cell viability and tightly-controlled diameters in the range of 70-300 μm. The polydispersity of cell-laden PEG hydrogel microspheres as measured by % coefficient of variation was between 6% and 23% for all conditions tested. We established that our method was compatible with different cell types and that all tested cell types could be encapsulated at high densities of 10⁶-10⁹ and ≥90% encapsulation efficiency. We observed cell aggregation within the hydrogel microspheres at applied voltage >5 kV. Since PEG is a synthetic polymer devoid of cell attachment sites, we could overcome this limitation by tethering Arg-Gly-Asp-Ser (RGDS) peptide to the PEG hydrogel microspheres; upon RGDS tethering, we observed uniform cell dispersion. The microencapsulated cells could be cultured in the PEG hydrogel microspheres of different sizes for up to one week without significant loss in cell viability. In conclusion, the EHS technique developed here could be used to generate cell-laden PEG hydrogel microspheres of controlled sizes for potential applications in cell delivery and organoid cultures.

Development and Pre-Clinical Evaluation of Recombinant Human Myelin Basic Protein Nano Therapeutic Vaccine in Experimental Autoimmune Encephalomyelitis Mice Animal Model

Recombinant human myelin basic protein (rhMBP) was previously produced in the milk of transgenic cows. Differences in molecular recognition of either hMBP or rhMBP by surface-immobilized anti-hMBP antibodies were demonstrated. This indicated differences in immunological response between rhMBP and hMBP. Here, the activity of free and controlled release rhMBP poly(ε-caprolactone) nanoparticles (NPs), as a therapeutic vaccine against multiple sclerosis (MS) was demonstrated in experimental autoimmune encephalomyelitis (EAE) animal model. Following optimization of nanoformulation, discrete spherical, rough-surfaced rhMBP NPs with high entrapment efficiency and controlled release pattern were obtained. Results indicated that rhMBP was loaded into and electrostatically adsorbed onto the surface of NPs. Subcutaneous administration of free or rhMBP NPs before EAE-induction reduced the average behavioral score in EAE mice and showed only mild histological alterations and preservation of myelin sheath, with rhMBP NPs showing increased protection. Moreover, analysis of inflammatory cytokines (IFN-γ and IL-10) in mice brains revealed that pretreatment with free or rhMBP NPs significantly protected against induced inflammation.

IN CONCLUSION

i) rhMBP ameliorated EAE symptoms in EAE animal model, ii) nanoformulation significantly enhanced efficacy of rhMBP as a therapeutic vaccine and iii) clinical investigations are required to demonstrate the activity of rhMBP NPs as a therapeutic vaccine for MS.

Practically feasible production of sustained-release microspheres of granulocyte-macrophage colony-stimulating factor (rhGM-CSF)

Using recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) as a model drug, the present study demonstrated a practically feasible process to produce polymeric microspheres for sustained-release delivery of protein drugs with preserved integrity. This process is featured with pre-loading proteins into polysaccharide fine particles via a self-standing aqueous-aqueous "emulsion", prior to microencapsulation into the microspheres. The protein drug, rhGM-CSF, was partitioned thermodynamically into a dextran dispersed phase of the aqueous-aqueous emulsion, followed by lyophilization and removal of the polyethylene glycol (PEG) continuous phase (using an organic solvent not penetrating into dextran matrix). The harvested dextran particles were then suspended in a dichloromethane solution of polylatic-co-glyclic acids (PLGA) and emulsified in a polyvinyl alcohol (PVA) and NaCl solution of small volume to form embryonic microspheres. The emulsion was then transferred into a NaCl solution of large volume to extract the organic solvent and harden the embryonic microspheres. The obtained rhGM-CSF microspheres showed a satisfied release profile with the day-to-day variation within 9 folds over the multi-weeks long release period. At the same time, the integrity (defined freedom of aggregates measured by SEC-HPLC) and bioactivity (defined by TF-1 cell proliferation) of the proteins were well preserved. The present formulation process ensured good reproducibility and over 89% protein encapsulation efficiency, and practically feasible to adapt to scaled productions.

Design of experiments for microencapsulation applications: A review

Microencapsulation techniques have been intensively explored by many research sectors such as pharmaceutical and food industries. Microencapsulation allows to protect the active ingredient from the external environment, mask undesired flavours, a possible controlled release of compounds among others. The purpose of this review is to provide a background of design of experiments in microencapsulation research context. Optimization processes are required for an accurate research in these fields and therefore, the right implementation of micro-sized techniques at industrial scale. This article critically reviews the use of the response surface methodologies in pharmaceutical and food microencapsulation research areas. A survey of optimization procedures in the literature, in the last few years is also presented.

Strategies to Develop Inhibitors of Motif-Mediated Protein-Protein Interactions as Drug Leads

Protein-protein interactions are fundamental for virtually all functions of the cell. A large fraction of these interactions involve short peptide motifs, and there has been increased interest in targeting them using peptide-based therapeutics. Peptides benefit from being specific, relatively safe, and easy to produce. They are also easy to modify using chemical synthesis and molecular biology techniques. However, significant challenges remain regarding the use of peptides as therapeutic agents. Identification of peptide motifs is difficult, and peptides typically display low cell permeability and sensitivity to enzymatic degradation. In this review, we outline the principal high-throughput methodologies for motif discovery and describe current methods for overcoming pharmacokinetic and bioavailability limitations.

Preparation and characterization of biodegradable polyhydroxybutyrate-co-hydroxyvalerate/polyethylene glycol-based microspheres

The in vivo effectiveness of biomolecules may be limited by their rapid diffusion in the body and short half-life time. Encapsulation of these biomolecules allows protecting them against degradation and ensuring a controlled release over time. In this work, the production of polyhydroxybutyrate-co-hydroxyvalerate/polyethylene glycol-based microspheres loaded with heparin by double emulsion-solvent evaporation is investigated. Significant improvements are achieved after blending PHB-HV microspheres with PEG. First of all, an important decrease of the initial burst effect is ensured. Moreover, lower degradation of the microspheres is observed after 30days in the release medium. Finally, the release rate could be controlled using different PEG molecular weights and concentrations. A toxic effect of PHB-HV 30% PEG 1100gmol^-1 microspheres is observed whereas PHB-HV and PHB-HV 30% PEG 10,000gmol^-1 microspheres are not toxic. These microspheres seem to be most suited for further tissue engineering applications. The effectiveness of direct PEG blending to PHB-HV is proved, limiting the use of chemical reagents for PHB-HV/PEG copolymer synthesis and steps for chemical reagents removal from the copolymer.

Strengths, weaknesses, opportunities and challenges for long acting injectable therapies: Insights for applications in HIV therapy

Advances in solid drug nanoparticle technologies have resulted in a number of long-acting (LA) formulations with the potential for once monthly or longer administration. Such formulations offer great utility for chronic diseases, particularly when a lack of medication compliance may be detrimental to treatment response. Two such formulations are in clinical development for HIV but the concept of LA delivery has its origins in indications such as schizophrenia and contraception. Many terms have been utilised to describe the LA approach and standardisation would be beneficial. Ultimately, definitions will depend upon specific indications and routes of delivery, but for HIV we propose benchmarks that reflect perceived clinical benefits and available data on patient attitudes. Specifically, we propose dosing intervals of ≥1week, ≥1month or ≥6months, for oral, injectable or implantable strategies, respectively. This review focuses upon the critical importance of potency in achieving the LA outcome for injectable formulations and explores established and emerging technologies that have been employed across indications. Key technological challenges such as the need for consistency and ease of administration for drug combinations, are also discussed. Finally, the review explores the gaps in knowledge regarding the pharmacology of drug release from particulate-based LA injectable suspensions. A number of hypotheses are discussed based upon available data relating to local drug metabolism, active transport systems, the lymphatics, macrophages and patient-specific factors. Greater knowledge of the mechanisms that underpin drug release and protracted exposure will help facilitate further development of this strategy to achieve the promising clinical benefits.

Stimuli-Responsive Block Copolymer-Based Assemblies for Cargo Delivery and Theranostic Applications

Although a number of tactics towards the fabrication and biomedical exploration of stimuli-responsive polymeric assemblies being responsive and adaptive to various factors have appeared, the controlled preparation of assemblies with well-defined physicochemical properties and tailor-made functions are still challenges. These responsive polymeric assemblies, which are triggered by stimuli, always exhibited reversible or irreversible changes in chemical structures and physical properties. However, simple drug/polymer nanocomplexes cannot deliver or release drugs into the diseased sites and cells on-demand due to the inevitable biological barriers. Hence, utilizing therapeutic or imaging agents-loaded stimuli-responsive block copolymer assemblies that are responsive to tumor internal microenvironments (pH, redox, enzyme, and temperature, etc.) or external stimuli (light and electromagnetic field, etc.) have emerged to be an important solution to improve therapeutic efficacy and imaging sensitivity through rationally designing as well as self-assembling approaches. In this review, we summarize a portion of recent progress in tumor and intracellular microenvironment responsive block copolymer assemblies and their applications in anticancer drug delivery and triggered release and enhanced imaging sensitivity. The outlook on future developments is also discussed. We hope that this review can stimulate more revolutionary ideas and novel concepts and meet the significant interest to diverse readers.

Control of silk microsphere formation using polyethylene glycol (PEG)

A one step, rapid method to prepare silk microspheres was developed, with particle size controlled by the addition of polyethylene glycol (PEG). PEG molecular weight (4.0K-20.0KDa) and concentration (20-50wt%), as well as silk concentration (5-20wt%), were key factors that determined particle sizes varying in a range of 1-100μm. Addition of methanol to the PEG-silk combinations increased the content of crystalline β-sheet in the silk microspheres. To track the distribution and degradation of silk microspheres in vivo, 3-mercaptopropionic acid (MPA)-coated CdTe quantum dots (QDs) were physically entrapped in the silk microspheres. QDs tightly bound to the β-sheet domains of silk via hydrophobic interactions, with over 96% of the loaded QDs remaining in the silk microspheres after exhaustive extraction. The fluorescence of QDs-incorporated silk microspheres less stable in cell culture medium than in phosphate buffer solution (PBS) and water. After subcutaneous injection in mice, microspheres prepared from 20% silk (approx. 30μm diameter particles) still fluoresced at 24h, while those prepared from 8% silk (approx. 4μm diameter particles) and free QDs were not detectable, reflecting the QDs quenching and particle size effect on microsphere clearance in vivo. The larger microspheres were more resistant to cell internalization and degradation. Since PEG is an FDA-approved polymer, and silk is FDA approved for some medical devices, the methods developed in the present study will be useful in a variety of biomedical applications where simple, rapid and scalable preparation of silk microspheres is required.

STATEMENT OF SIGNIFICANCE

The work is of significance to the biomaterial and controlled release society because it provides a new option for fabricating silk microspheres in one simple step of mixing silk and polyethylene glycol (PEG), with the size and properties of microspheres controllable by PEG molecular weight as well as PEG and silk concentrations. Although fabrication of silk microspheres have been reported previously using spray-drying, liposome-templating, polyvinyl alcohol (PVA) emulsification, etc., applications were hindered due to harsh conditions (temperature, solvents, etc.) and complicated procedures used as well as low yield and less controllable particle size (usually <10μm). Since PEG is an FDA-approved polymer, and silk is FDA approved for some medical devices, the methods developed in the present study will be useful in a variety of biomedical applications where simple, rapid and scalable preparation of silk microspheres is required.