Biodegradable microspheres for protein delivery

Effect of hydroxyethyl starch on drug stability and release of semaglutide in PLGA microspheres

The degradation of peptide drugs limits the application of peptide drug microspheres. Structural changes of peptides at the water-oil interface and the destruction of their spatial structure in the complex microenvironment during polymer degradation can affect drug release and in vivo biological activity. This study demonstrates that adding hydroxyethyl starch (HES) to the internal aqueous phase (W1) significantly enhances the stability of semaglutide and optimizes its release behavior in PLGA microspheres. The results showed that this improvement was due to a spontaneous exothermic reaction (ΔH = -132.20 kJ mol-1) facilitated by hydrogen bonds. Incorporating HES into the internal aqueous phase using the water-in-oil-in-water (W1/O/W2) emulsion method yielded PLGA microspheres with a high encapsulation rate of 94.38 %. Moreover, microspheres with HES demonstrated well-controlled drug release over 44 days, unlike the slower and incomplete release in microspheres without HES. The optimized h-MG2 formulation achieved a more complete drug release (83.23 %) and prevented 30.65 % of drug loss compared to the HES-free microspheres within the same period. Additionally, the optimized semaglutide microspheres provided nearly three weeks of glycemic control with adequate safety. In conclusion, adding HES to the internal aqueous phase improved the in-situ drug stability and release behavior of semaglutide-loaded PLGA microspheres, effectively increasing the peptide drug payload in PLGA microspheres.

Synthesis, characterization, and application of honey stabilized inulin nanoparticles as colon targeting drug delivery carrier

Inulin (INU) is a versatile natural polysaccharide primarily derived from chicory roots. INU possesses the unique quality of evading digestion or fermentation in the early stages of the human digestive tract, instead reaching the lower colon directly. Exploiting on this distinctive attribute, INU finds application in the creation of targeted carrier systems for delivering drugs tailored to colon-related diseases. This study presents a novel method for synthesizing highly stable and non-aggregatory inulin nanoparticles (INU NPs) by ionotropic gelation method, using calcium chloride as crosslinker and natural honey as a stabilizing agent. Different formulation and process parameters were optimized for the synthesis of monodispersed INU NPs. These INU NPs efficiently encapsulated a hydrophilic drug irinotecan hydrochloride trihydrate (IHT) and drug loaded formulation (IINPs) demonstrated excellent colloidal and storage stabilities. Notably, these IINPs exhibited pH-dependent drug release, suggesting potential for colon-specific drug delivery. Anticancer activity of the NPs was found significantly higher in comparison to IHT through cytotoxicity and apoptosis studies against human colorectal carcinoma cells. Overall, this study revealed that the INU NPs synthesized by ionotropic gelation will be an efficient nanocarrier system for colon-targeted drug delivery due to their exceptional biocompatibility and stability in stomach and upper intestinal conditions.

Pioneering a paradigm shift in tissue engineering and regeneration with polysaccharides and proteins-based scaffolds: A comprehensive review

In the realm of modern medicine, tissue engineering and regeneration stands as a beacon of hope, offering the promise of restoring form and function to damaged or diseased organs and tissues. Central to this revolutionary field are biological macromolecules-nature's own blueprints for regeneration. The growing interest in bio-derived macromolecules and their composites is driven by their environmentally friendly qualities, renewable nature, minimal carbon footprint, and widespread availability in our ecosystem. Capitalizing on these unique attributes, specific composites can be tailored and enhanced for potential utilization in the realm of tissue engineering (TE). This review predominantly concentrates on the present research trends involving TE scaffolds constructed from polysaccharides, proteins and glycosaminoglycans. It provides an overview of the prerequisites, production methods, and TE applications associated with a range of biological macromolecules. Furthermore, it tackles the challenges and opportunities arising from the adoption of these biomaterials in the field of TE. This review also presents a novel perspective on the development of functional biomaterials with broad applicability across various biomedical applications.

Single Infrared Spectrum Enables Simultaneous Identification of (Bio)Chemical Nature and Particle Size of Microorganisms and Synthetic Microplastic Beads

Populations of nearly identical chemical and biological microparticles include the synthetic microbeads used in cosmetic, biomedical, agri-food, and pharmaceutical industries as well as the class of living microorganisms such as yeast, pollen, and biological cells. Herein, we identify simultaneously the size and chemical nature of spherical microparticle populations with diameters larger than 1 μm. Our analysis relies on the extraction of both physical and chemical signatures from the same optical spectrum recorded using attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectroscopy. These signatures are the spectral resonances caused by the microparticles, which depend on their size and the absorption peaks revealing their chemical nature. We validate the method first on separated and mixed groups of spherical microplastic particles of two different diameters, where the method is used to calculate the diameter of the microspherical particles. Then, we apply the method to correctly identify and measure the diameter of Saccharomyces cerevisiae yeast cells. Theoretical simulations to help in understanding the effect of size distribution and dispersion support our results.

Bromelain: a review of its mechanisms, pharmacological effects and potential applications

The utilization of plant-derived supplements for disease prevention and treatment has long been recognized because of their remarkable potential. Ananas comosus, commonly known as pineapple, produces a group of enzymes called bromelain, which contains sulfhydryl moieties. Recent studies have shown that bromelain exhibits a wide range of activities, including anti-inflammatory, anti-diabetic, anti-cancer, and anti-rheumatic properties. These properties make bromelain a promising drug candidate for the treatment of various diseases. The anti-inflammatory activity of bromelain has been shown to be useful in treating inflammatory conditions such as osteoarthritis, rheumatoid arthritis, and asthma, whereas the anti-cancer activity of bromelain is via induction of apoptosis, inhibition of angiogenesis, and enhancement of the body's immune response. The anti-diabetic property of bromelain is owing to the improvement in glucose metabolism and reduction in insulin resistance. The therapeutic potential of bromelain has been investigated in numerous preclinical and clinical studies and a number of patents have been granted to date. Various formulations and delivery systems are being developed in order to improve the efficacy and safety of this molecule, including the microencapsulated form to treat oral inflammatory conditions and liposomal formulations to treat cancer. The development of novel drug delivery systems and formulations has further ameliorated the therapeutic potential of bromelain by improving its bioavailability and stability, while reducing the side effects. This review intends to discuss various properties and therapeutic applications of bromelain, along with its possible mechanism of action in treating various diseases. Recent patents and clinical trials concerning bromelain have also been covered.

Intramuscular, extended-release naltrexone inadvertently administered in the deltoid muscle: A case report

BACKGROUND

Extended-release, intramuscular (IM) naltrexone can be an effective and convenient medication option for alcohol use disorder. We sought to assess the clinical impact of an alternate, if inadvertent, administration of IM naltrexone in the deltoid muscle instead of the recommended gluteal muscle.

CASE SUMMARY

IM naltrexone was prescribed to a hospitalized 28-year-old man with severe alcohol use disorder as part of an inpatient clinical trial. A nurse unfamiliar with naltrexone administration mistakenly administered the drug to the deltoid instead of the gluteal muscle recommended by the manufacturer. Despite concerns that injection of the large-volume suspension to the smaller muscle would potentially contribute to increased pain and higher chance of adverse events owing to faster medication absorption, the patient experienced only mild discomfort to the deltoid region, without other adverse events on immediate physical and laboratory examinations. The patient later denied additional adverse events in the period after hospitalization, but he did not endorse any anti-craving effect of the medication, resuming drinking alcohol quickly following initial discharge.

PRACTICE IMPLICATIONS

This case represents a unique procedural challenge of administering a medication in the inpatient setting that is typically given in the outpatient setting. Inpatient staff members frequently rotate and may be relatively unfamiliar with IM naltrexone, so handling should be limited to personnel who have received focused training on its administration. Fortunately, in this case deltoid administration of naltrexone was well-tolerated and even deemed quite "acceptable" to the patient. Clinically, the medication was insufficiently effective, but biopsychosocial context may have made his AUD especially refractory. More research is needed to fully establish whether naltrexone given via deltoid muscle injection has comparable safety and efficacy to gluteal muscle administration.

Biocompatible polymeric microparticles serve as novel and reliable vehicles for exogenous hormone manipulations in passerines

The administration of exogenous hormones emerged as an essential tool for field studies in endocrinology. However, working with wild animals remains challenging, because under field conditions not every available method meets the necessary requirements. Achieving a sustained elevation in hormone levels, while simultaneously minimising handling time and invasiveness of the procedure is a difficult task in field endocrinology. Facing this challenge, we have investigated the suitability of biocompatible polymeric microparticles, a novel method for drug-administration, as a tool to manipulate hormones in small songbirds. We chose the insulin-like growth factor-1 (IGF-1) as target hormone, because it receives great interest from the research community due to its important role in shaping life-history traits. Moreover, its short half-life and hydrophilic properties imply a major challenge in finding a suitable method to achieve a sustained, systemic long-term release. To study the release kinetics, we injected either IGF-1 loaded polylactic-co-glycolic acid (PLGA) microparticles or dispersion medium (control group) in the skin pocket of the interscapular region of captive bearded reedlings (Panurus biarmicus). We collected blood samples for 7 consecutive days plus an additional sampling period after two weeks and complemented these with an in vitro experiment. Our results show that in vitro, PLGA microparticles allowed a stable IGF-1 release for more than 15 days, following a burst release at the beginning of the measurement. In vivo, the initial burst was followed by a drop to still elevated levels in circulating IGF-1 until the effect vanished by 16 days post-treatment. This study is the first to describe the use of PLGA-microparticles as a novel tool for exogenous hormone administration in a small passerine. We suggest that this method is highly suitable to achieve the systemic long-term release of hydrophilic hormones with short half-life and reduces overall handling time, as it requires only one subcutaneous injection.

The Management of Parkinson's Disease: An Overview of the Current Advancements in Drug Delivery Systems

Parkinson's disease (PD) has significantly affected a large proportion of the elderly population worldwide. According to the World Health Organization, approximately 8.5 million people worldwide are living with PD. In the United States, an estimated one million people are living with PD, with approximately 60,000 new cases diagnosed every year. Conventional therapies available for Parkinson's disease are associated with limitations such as the wearing-off effect, on-off period, episodes of motor freezing, and dyskinesia. In this review, a comprehensive overview of the latest advances in DDSs used to reduce the limitations of current therapies will be presented, and both their promising features and drawbacks will be discussed. We are also particularly interested in the technical properties, mechanism, and release patterns of incorporated drugs, as well as nanoscale delivery strategies to overcome the blood-brain barrier.

Recent advances in microbeads-based drug delivery system for achieving controlled drug release

Novel drug delivery system endows a beneficial method for achieving a desired drug concentration at the appropriate site in the body. The concept of targeted drug delivery has been emerged to localize the drug in the targeted tissue of interest while reducing the relative concentration of the medication in the surrounding tissues. This could be easily accomplished by using different multi-particulate dosage forms like pellets, granules, microcapsules, liposomes, beads. But the major drawbacks associated with them are the use of harsh chemicals and an elevated temperature for their preparation. Preparation of microbeads by ionotropic gelation and emulsion gelation method overcomes these problems by neither using harsh chemicals nor elevated temperature for their preparation. Thus, this can be proved to be a better alternative over other dosage forms. Several parameters were studied in terms of their morphology, particle size, encapsulation efficiency, swelling ratio, mucoadhesivity, etc. The endeavor of present article is toward presenting a wider perspective of the comprehensive knowledge available in the field of microbeads. Thus, the intent of this review is to recapitulate the relevance of microbeads.

Formulation and Evaluation of Pravastatin Sodium-Loaded PLGA Nanoparticles: In vitro-in vivo Studies Assessment

Purpose

Pravastatin sodium (PVS) is a hypolipidemic drug which suffers from extensive first-pass metabolism and short half-life. Poly(d,l-lactide-co-glycolide) (PLGA) is considered a promising carrier to improve its hypolipidemic and hepatoprotective activities.

Methods

PVS-loaded PLGA nanoparticles (PVS-PLGA-NPs) were prepared by double emulsion method using a full 3² factorial design. The in vitro release and the physical stability studies of the optimized PVS-PLGA-NPs (F5) were performed. Finally, both hypolipidemic and hepatoprotective activities of the optimized F5 NPs were studied and compared to PVS solution.

Results

All the studied physical parameters of the prepared NPs were found in the accepted range. The particle size (PS) ranged from 90 ± 0.125 nm to 179.33 ± 4.509 nm, the poly dispersity index (PDI) ranged from 0.121 ± 0.018 to 0.158 ± 0.014. The optimized NPs (F5) have the highest entrapment efficiency (EE%) (51.7 ± 5%), reasonable PS (168.4 ± 2.506 nm) as well as reasonable zeta potential (ZP) (-28.3 ± 1.18mv). Solid-state characterization indicated that PVS is well entrapped into NPs. All NPs have distinct spherical shape with smooth surface. The prepared NPs showed a controlled release profile. F5 showed good stability at 4 ± 2°C during the whole storage period of 3 months. In vivo study and histopathological examination indicated that F5 NPs showed significant increase in PVS hypolipidemic as well as hepatoprotective activity compared to PVS solution.

Conclusion

The PVS-PLGA-NPs could be considered a promising model to evade the first-pass effect and showed improvement in the hypolipidemic and hepatoprotective activities compared to PVS solution.

Nanoparticles and convergence of artificial intelligence for targeted drug delivery for cancer therapy: Current progress and challenges

Cancer is a life-threatening disease, resulting in nearly 10 million deaths worldwide. There are various causes of cancer, and the prognostic information varies in each patient because of unique molecular signatures in the human body. However, genetic heterogeneity occurs due to different cancer types and changes in the neoplasms, which complicates the diagnosis and treatment. Targeted drug delivery is considered a pivotal contributor to precision medicine for cancer treatments as this method helps deliver medication to patients by systematically increasing the drug concentration on the targeted body parts. In such cases, nanoparticle-mediated drug delivery and the integration of artificial intelligence (AI) can help bridge the gap and enhance localized drug delivery systems capable of biomarker sensing. Diagnostic assays using nanoparticles (NPs) enable biomarker identification by accumulating in the specific cancer sites and ensuring accurate drug delivery planning. Integrating NPs for cancer targeting and AI can help devise sophisticated systems that further classify cancer types and understand complex disease patterns. Advanced AI algorithms can also help in biomarker detection, predicting different NP interactions of the targeted drug, and evaluating drug efficacy. Considering the advantages of the convergence of NPs and AI for targeted drug delivery, there has been significantly limited research focusing on the specific research theme, with most of the research being proposed on AI and drug discovery. Thus, the study's primary objective is to highlight the recent advances in drug delivery using NPs, and their impact on personalized treatment plans for cancer patients. In addition, a focal point of the study is also to highlight how integrating AI, and NPs can help address some of the existing challenges in drug delivery by conducting a collective survey.

Enteric Polymer-Coated Porous Silicon Nanoparticles for Site-Specific Oral Delivery of IgA Antibody

Porous silicon (pSi) nanoparticles are loaded with Immunoglobulin A-2 (IgA2) antibodies, and the assembly is coated with pH-responsive polymers on the basis of the Eudragit family of enteric polymers (L100, S100, and L30-D55). The temporal release of the protein from the nanocomposite formulations is quantified following an in vitro protocol simulating oral delivery: incubation in simulated gastric fluid (SGF; at pH 1.2) for 2 h, followed by a fasting state simulated intestinal fluid (FasSIF; at pH 6.8) or phosphate buffer solution (PBS; at pH 7.4). The nanocomposite formulations display a negligible release in SGF, while more than 50% of the loaded IgA2 is released in solutions at a pH of 6.8 (FasSIF) or 7.4 (PBS). Between 21 and 44% of the released IgA2 retains its functional activity. A capsule-based system is also evaluated, where the IgA2-loaded particles are packed into a gelatin capsule and the capsule is coated with either EudragitL100 or EudragitS100 polymer for a targeted release in the small intestine or the colon, respectively. The capsule-based formulations outperform polymer-coated nanoparticles in vitro, preserving 45-54% of the activity of the released protein.

A Review of Multifunction Smart Nanoparticle based Drug Delivery Systems

Cancer nano-therapeutics are rapidly evolving and are often used to overcome a number of concerns with traditional drug delivery methods, including non-specific drug targeting and distribution, low oral bioavailability, and poor hydrophilicity. Modern nano-based targeting techniques have been developed as a result of advances in nano vehicle engineering and materials science, which may bring people with cancer a new hope. Clinical trials have been authorized for a number of medicinal nanocarriers. Nanocarriers with the best feasible size and surface attributes have been developed to optimize biodistribution and increase blood circulation duration. Nanotherapeutics can carry preloaded active medicine towards cancerous cells by preferentially leveraging the specific physiopathology of malignancies. In contrast to passive targeting, active targeting strategies involving antigens or ligands, developed against specific tumor sites, boost the selectivity of these curative nanovehicles. Another barrier that nanoparticles may resolve or lessen is drug resistance. Multifunctional and complex nanoparticles are currently being explored and are predicted to usher in a new era of nanoparticles that will allow for more individualized and customized cancer therapy. The potential prospects and opportunities of stimuli-triggered nanosystems in therapeutic trials are also explored in this review.

Fabrication of multifunctional alginate microspheres containing hydroxyapatite powder for simultaneous cell and drug delivery

Novel alginate-hydroxyapatite hybrid microspheres were developed for simultaneous delivery of drugs and cells as a multifunctional bone substitute for osteoporotic bone tissue regeneration. The microspheres were used to enhance osteogenesis and to carry and deliver quercetin, a representative phytoestrogen that controls bone tissue regeneration metabolism in osteoporosis patients, through sustained release over a long period. To overcome quercetin’s hydrophobicity and low solubility in aqueous environments, we added it to the surface of hydroxyapatite (HAp) nanoparticles before mixing them with an alginate solution. The homogeneous distribution of the HAp nanoparticles in the alginate solution was essential for preventing nozzle clogging and achieving successfully fabricated hybrid microspheres. To this end, a 3D ultrasonic treatment was applied. Electrostatic microencapsulation was then used to fabricate hybrid alginate-HAp microspheres containing quercetin and cells. The microspheres were approximately 290.7 ± 42.5 μm (aspect ratio of 1). The sustained release of quercetin was confirmed during a test period of 20 weeks. The cells in the hybrid microspheres maintained good cell viability during the entire testing period, and their osteogenic differentiation behavior was boosted by the presence of HAp. Thus, osteogenic differentiation could be greatly improved by adding quercetin. These novel multi-biofunctional hybrid microspheres have great potential for the regeneration of osteoporotic bone tissue at indeterminate defect sites.

The industrial design, translation, and development strategies for long-acting peptide delivery

INTRODUCTION

Peptides are widely recognized as therapeutic agents in the treatment of a wide range of diseases, such as cancer, diabetes etc. However, their use has been limited by their short half-life, due to significant metabolism by exo- and endo-peptidases as well as their inherent poor physical and chemical stability. Research with the aim of improving their half-life in the body, and thus improving patient compliance (by decreasing the frequency of injections) has gained significant attention.

AREAS COVERED

This review outlines the current landscape and industrial approaches to achieve extended peptide exposure and reduce dosing frequency. Emphasis is placed on identifying challenges in drug product manufacturing and desirable critical quality attributes that are essential for activity and safety, providing insights into chemistry and design aspects impacting peptide release, and summarizing important considerations for CMC developability assessments of sustained release peptide drugs.

EXPERT OPINION

Bring the patient and disease perspective early into development. Substantial advances have been made in the field of sustained delivery of peptides despite their complexity. The article will also highlight considerations for early-stage product design and development, providing an industrial perspective on risk mitigation in developing sustained release peptide drug products.

PLGA Carriers for Controlled Release of Levofloxacin in Anti-Tuberculosis Therapy

Levofloxacin (LFX) is a highly effective anti-tuberculosis drug with a pronounced bactericidal activity against Mycobacterium tuberculosis (Mtb). In this work, an “organic solvent-free” approach has been used for the development of polylactic-co-glycolic acid (PLGA) microparticles and scaffolds containing LFX at a therapeutically significant concentration, providing for its sustained release. To achieve the target, both nonpolar supercritical carbon dioxide and polar supercritical trifluoromethane have been used. By changing the composition, surface morphology, size, and internal structure of the polymer carriers, one can control the kinetics of the LFX release into phosphate buffered saline solutions and physiological media, providing for its acceptable burst and desirable concentration in the prolonged phase. The biocompatibility and bactericidal efficacy of PLGA/LFX carriers assessed both in vitro (against Mtb phagocytosed by macrophages) and in vivo (against inbred BALB/c mice aerogenically infected with Mtb) demonstrated their anti-tuberculosis activity comparable with that of the standard daily intragastric levofloxacin administration. These results make it possible to consider the developed compositions as a promising candidate for anti-tuberculosis control release formulations providing for the further evaluation of their activity against Mtb and their metabolism in vivo over long periods of tuberculosis infection.

Intra-amniotic Injection of Poly(lactic-co-glycolic Acid) Microparticles Loaded with Growth Factor: Effect on Tissue Coverage and Cellular Apoptosis in the Rat Model of Myelomeningocele

BACKGROUND

Myelomeningocele (MMC) is a devastating congenital neurologic disorder that can lead to lifelong morbidity and has limited treatment options. This study investigates the use of poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs) loaded with fibroblast growth factor (FGF) as a platform for in utero treatment of MMC.

STUDY DESIGN

Intra-amniotic injections of PLGA MPs were performed on gestational day 17 (E17) in all-trans retinoic acid-induced MMC rat dams. MPs loaded with fluorescent dye (DiO) were evaluated 3 hours after injection to determine incidence of binding to the MMC defect. Fetuses were then treated with PBS or PLGA particles loaded with DiO, bovine serum albumin, or FGF and evaluated at term (E21). Fetuses with MMC defects were evaluated for gross and histologic evidence of soft tissue coverage. The effect of PLGA-FGF treatment on spinal cord cell death was evaluated using an in situ cell death kit.

RESULTS

PLGA-DiO MPs had a binding incidence of 86% and 94% 3 hours after injection at E17 for doses of 0.1 mg and 1.2 mg, respectively. Incidence of soft tissue coverage at term was 19% (4 of 21), 22% (2 of 9), and 83% (5 of 6) for PLGA-DiO, PLGA-BSA, and PLGA-FGF, respectively. At E21, the percentage of spinal cord cells positive for in situ cell death was significantly higher in MMC controls compared with wild-type controls or MMC pups treated with PLGA-FGF.

CONCLUSION

PLGA MPs are an innovative minimally invasive platform for induction of soft tissue coverage in the rat model of MMC and may reduce cellular apoptosis.

Compatibility and Durability of the Gel Stent Material

INTRODUCTION

The XEN Gel Stent (AbbVie Pharmaceuticals) is a device made from Gelatin; a well-known material in the medical field that is firm enough to hold its shape and soft enough to conform to tissues and reduce the risk of erosion. The Gel Stent creates a permanent outflow connection between the anterior chamber and subconjunctival space.

AREAS COVERED

Validation testing done on the Gel Stent to evaluate biocompatibility and durability of the material as well as real-world experience are included and discussed in this paper.

EXPERT OPINION

Correlating the results of the preclinical testing, study outcomes available in the published literature, and the surgeons' experiences, the device and materials have shown to have an acceptable biocompatibility and durability profile, with a stable, nondegradable, and permanent implant.

Drug molecules bridge with small gatekeeper to co-block mesoporous silica nanoparticles for drug delivery

In this study, a filter-like blocking system based on MSN with small gatekeeper 5- mercapto-2 nitrobenzoic acid (MNBA) has developed. The MNBA grafted nanoparticle MSN-SS-MNBA shows excellent blocking performance with negligible leakage when loaded with doxorubicin (DOX), and the release profiles illustrate stimuli-responsive property when triggered by GSH. Viability experiments indicate that MSN-SS-MNBA has obvious inhibition for both Hela cells and HCT116 cells, while showing good biocompatibility for L929 cells, which suggests that the modified MNBA has a synergistic effect on cancer cells-killing. Since the small grafted molecule MNBA cannot block the channels of MSN via self-assembly, a filter-like blocking model that the loaded drug bridged with modified MNBA to fulfill the blocking process is proposed. The novel blocking strategy provides a new possible way for pore blocking, and the small nanovalve can be used as synergistic molecule for cancer therapy.

Mechanical characterization of rose bengal and green light crosslinked collagen scaffolds for regenerative medicine

Collagen is one of the most important biomaterials for tissue engineering approaches. Despite its excellent biocompatibility, it shows the non-negligible disadvantage of poor mechanical stability. Photochemical crosslinking with rose bengal and green light (RGX) is an appropriate method to improve this property. The development of collagen laminates is helpful for further adjustment of the mechanical properties as well as the controlled release of incorporated substances. In this study, we investigate the impact of crosslinking and layering of two different collagen scaffolds on the swelling behavior and mechanical behavior in micro tensile tests to obtain information on its wearing comfort (stiffness, strength and ductility). The mechanical stability of the collagen material after degradation due to cell contact is examined using thickness measurements. There is no linear increase or decrease due to layering homologous laminates. Unexpectedly, a decrease in elongation at break, Young's modulus and ultimate tensile strength are measured when the untreated monolayer is compared to the crosslinked one. Furthermore, we can detect a connection between stability and cell proliferation. The results show that with variation in number and type of layers, collagen scaffolds with tailored mechanical properties can be produced. Such a multi-layered structure enables the release of biomolecules into inner or outer layers for biomedical applications.

Toxicology of Nanoparticles in Drug Delivery

Nanoparticles have revolutionized biomedicine especially in the field of drug delivery due to their intriguing properties such as systemic stability, level of solubility, and target site specificity. It can, however, be both beneficial and damaging depending on the properties in different environments, thus highlighting the importance of nanotoxicology studies before use in humans. Different types of nanoparticles have been used in drug delivery, and this review summarizes the recent toxicity studies of these nanoparticles. The toxicological evaluation of three widely used nanoparticles in drug delivery that are metal, lipid, and protein nanoparticles has been discussed in detail. Studies have recorded several toxic effects of various nanoparticles such as metal-based nanoparticles have been linked to increased oxidative stress and have the potential to infiltrate the cell nucleus and protein-based nanoparticles have been observed to have hepatotoxicity and nephrotoxicity as their adverse effects. Considering the increasing application of nanoparticles in drug delivery and the growing concerns of regulatory authorities regarding the toxicity of nanocarriers in living organisms, it requires urgent attention to identify the gap in toxicity studies. The review highlights the gap in toxicity studies and potential focus areas to overcome the existing challenges.

PLGA/PLA-Based Long-Acting Injectable Depot Microspheres in Clinical Use: Production and Characterization Overview for Protein/Peptide Delivery

Over the past few decades, long acting injectable (LAI) depots of polylactide-co-glycolide (PLGA) or polylactic acid (PLA) based microspheres have been developed for controlled drug delivery to reduce dosing frequency and to improve the therapeutic effects. Biopharmaceuticals such as proteins and peptides are encapsulated in the microspheres to increase their bioavailability and provide a long release period (days or months) with constant drug plasma concentration. The biodegradable and biocompatible properties of PLGA/PLA polymers, including but not limited to molecular weight, end group, lactide to glycolide ratio, and minor manufacturing changes, could greatly affect the quality attributes of microsphere formulations such as release profile, size, encapsulation efficiency, and bioactivity of biopharmaceuticals. Besides, the encapsulated proteins/peptides are susceptible to harsh processing conditions associated with microsphere fabrication methods, including exposure to organic solvent, shear stress, and temperature fluctuations. The protein/peptide containing LAI microspheres in clinical use is typically prepared by double emulsion, coacervation, and spray drying techniques. The purpose of this review is to provide an overview of the formulation attributes and conventional manufacturing techniques of LAI microspheres that are currently in clinical use for protein/peptides. Furthermore, the physicochemical characteristics of the microsphere formulations are deliberated.

A review of existing strategies for designing long-acting parenteral formulations: Focus on underlying mechanisms, and future perspectives

The need for long-term treatments of chronic diseases has motivated the widespread development of long-acting parenteral formulations (LAPFs) with the aim of improving drug pharmacokinetics and therapeutic efficacy. LAPFs have been proven to extend the half-life of therapeutics, as well as to improve patient adherence; consequently, this enhances the outcome of therapy positively. Over past decades, considerable progress has been made in designing effective LAPFs in both preclinical and clinical settings. Here we review the latest advances of LAPFs in preclinical and clinical stages, focusing on the strategies and underlying mechanisms for achieving long acting. Existing strategies are classified into manipulation of in vivo clearance and manipulation of drug release from delivery systems, respectively. And the current challenges and prospects of each strategy are discussed. In addition, we also briefly discuss the design principles of LAPFs and provide future perspectives of the rational design of more effective LAPFs for their further clinical translation.

Engineering Strategies for Immunomodulatory Cytokine Therapies - Challenges and Clinical Progress

Cytokines are immunoregulatory proteins involved in many pathological states with promising potential as therapeutic agents. A diverse array of cytokines have been studied in preclinical disease models since the 1950s, some of which became successful biopharmaceutical products with the advancement of recombinant protein technology in the 1980s. However, following these early approvals, clinical translation of these natural immune signaling molecules has been limited due to their pleiotropic action in many cell types, and the fact that they have evolved to act primarily locally in tissues. These characteristics, combined with poor pharmacokinetics, have hindered the delivery of cytokines via systemic administration routes due to dose-limiting toxicities. However, given their clinical potential and recent clinical successes in cancer immunotherapy, cytokines continue to be extensively pursued in preclinical and clinical studies, and a range of molecular and formulation engineering strategies are being applied to reduce treatment toxicity while maintaining or enhancing therapeutic efficacy. This review provides a brief background on the characteristics of cytokines and their history as clinical therapeutics, followed by a deeper discussion on the engineering strategies developed for cytokine therapies with a focus on the translational relevance of these approaches.

Long-term sustained release Poly(lactic-co-glycolic acid) microspheres of asenapine maleate with improved bioavailability for chronic neuropsychiatric diseases

Schizophrenia and bipolar disorder are severe chronic neuropsychiatric diseases, affecting hundreds of millions of people worldwide. Asenapine maleate (ASM) has been demonstrated as a safe and effective therapeutic agent under twice-daily administration. However, lower compliance is observed when patients are treated with ASM, which significantly limits its application in schizophrenia and bipolar disorder. Moreover, the low bioavailability of ASM caused by first-pass metabolism and poor aqueous solubility also impairs the treatment effect. A formulation of ASM with the property of long-term sustained release and improved bioavailability can be a solution to overcome these weaknesses. In this article, we prepared ASM-loaded poly(lactic-co-glycolic acid) (ASM-PLGA) microspheres through different techniques, including emulsification-solvent evaporation (ESE), Shirasu porous glass membrane emulsification (SPG-ME), and microfluidic method. In vitro and in vivo assessments demonstrated that uniform-sized microspheres generated by the microfluidic process sustainably released ASM throughout 40-days, showing low burst release and significantly improved bioavailability. The results suggest that ASM-PLGA microspheres prepared by the microfluidic method provide an efficient strategy to enhance the drug exposure of ASM as the treatment of chronic neuropsychiatric diseases. It is also evident that this microfluidic strategy has the potential to construct with other drugs, establishing long-acting formulations.

Biodegradable zwitterionic poly(carboxybetaine) microgel for sustained delivery of antibodies with extended stability and preserved function

Many recent innovative treatments are based on monoclonal antibodies (mAbs) and other protein therapies. Nevertheless, sustained subcutaneous, oral or pulmonary delivery of such therapeutics is limited by the poor stability, short half-life, and non-specific interactions between the antibody (Ab) and delivery vehicle. Protein stabilizers (osmolytes) such as carboxybetaine can prevent non-specific interactions within proteins. In this work, a biodegradable zwitterionic poly(carboxybetaine), pCB, based microgel covalently crosslinked with tetra(ethylene glycol) diacrylate (TTEGDA) was synthesized for Ab encapsulation. The resulting microgels were characterized via FTIR, diffusion NMR, small-angle neutron scattering (SANS), and cell culture studies. The microgels were found to contain up to 97.5% water content and showed excellent degradability that can be tuned with crosslinking density. Cell compatibility of the microgel was studied by assessing the toxicity and immunogenicity in vitro. Cells exposed to microgel showed complete viability and no pro-inflammatory secretion of interleukin 6 (IL6) or tumor necrosis factor-alpha (TNFα). Microgel was loaded with Immunoglobulin G (as a model Ab), using a post-fabrication loading technique, and Ab sustained release from microgels of varying crosslinking densities was studied. The released Abs (especially from the high crosslinked microgels) proved to be completely active and able to bind with Ab receptors. This study opens a new horizon for scientists to use such a platform for local delivery of Abs to the desired target with minimized non-specific interactions.

Self-Encapsulation of Biomacromolecule Drugs in Porous Microscaffolds with Aqueous Two-Phase Systems

At present, the most commonly used methods of microencapsulation of protein drugs such as spray drying, multiple emulsification, and phase separation, can easily cause the problem of protein instability, which leads to low bioavailability and uncontrolled release of protein drugs. Herein, a novel method to encapsulate protein drugs into porous microscaffolds effectively and stably was described. Ammonium hydrogen carbonate (NH₄HCO₃) was employed to prepare porous microscaffolds. α-Amylase was encapsulated into the porous microscaffolds without denaturing conditions by an aqueous two-phase system (PEG/Sulfate). The pores were closed by heating above the glass transition temperature to achieve a sustained release of microscaffolds. The pore-closed microscaffolds were characterized and released in vitro. The integrity and activity of protein drugs were investigated to verify that this method was friendly to protein drugs. Results showed that the pores were successfully closed and a high loading amount of 9.67 ± 6.28% (w/w) was achieved. The pore-closed microscaffolds released more than two weeks without initial burst, and a high relative activity (92% compared with native one) of protein demonstrated the feasibility of this method for protein drug encapsulation and delivery.

Evaluation of the Hemocompatibility and Anticancer Potential of Poly(ε-Caprolactone) and Poly(3-Hydroxybutyrate) Microcarriers with Encapsulated Chrysin

In this work, novel chrysin-loaded poly(ε-caprolactone) and poly(3-hydroxybutyrate) microcarriers were synthesized according to a modified oil-in-water single emulsion/solvent evaporation method, utilizing poly(vinyl alcohol) surfactant as stabilizer and dispersing agent for the emulsification, and were evaluated for their physico-chemical and morphological properties, loading capacity and entrapment efficiency and in vitro release of their load. The findings suggest that the novel micro-formulations possess a spherical and relatively wrinkled structure with sizes ranging between 2.4 and 24.7 µm and a highly negative surface charge with z-potential values between (-18.1)-(-14.1) mV. The entrapment efficiency of chrysin in the poly(ε-caprolactone) and poly(3-hydroxybutyrate) microcarriers was estimated to be 58.10% and 43.63%, whereas the loading capacity was found to be 3.79% and 15.85%, respectively. The average release percentage of chrysin was estimated to be 23.10% and 18.01%, respectively. The novel micromaterials were further biologically evaluated for their hemolytic activity through hemocompatibility studies over a range of hematological parameters and cytoxicity against the epithelial human breast cancer cell line MDA-MB 231. The poly(ε-caprolactone) and poly(3-hydroxybutyrate) microcarriers reached an IC50 value with an encapsulated chrysin content of 149.19 µM and 312.18 µM, respectively, and showed sufficient blood compatibility displaying significantly low (up to 2%) hemolytic percentages at concentrations between 5 and 500 µg·mL-1.

A Safe GDNF and GDNF/BDNF Controlled Delivery System Improves Migration in Human Retinal Pigment Epithelial Cells and Survival in Retinal Ganglion Cells: Potential Usefulness in Degenerative Retinal Pathologies

We assessed the sustained delivery effect of poly (lactic-co-glycolic) acid (PLGA)/vitamin E (VitE) microspheres (MSs) loaded with glial cell-derived neurotrophic factor (GDNF) alone (GDNF-MSs) or combined with brain-derived neurotrophic factor (BDNF; GDNF/BDNF-MSs) on migration of the human adult retinal pigment epithelial cell-line-19 (ARPE-19) cells, primate choroidal endothelial (RF/6A) cells, and the survival of isolated mouse retinal ganglion cells (RGCs). The morphology of the MSs, particle size, and encapsulation efficiencies of the active substances were evaluated. In vitro release, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability, terminal deoxynucleotidyl transferase (TdT) deoxyuridine dUTP nick-end labelling (TUNEL) apoptosis, functional wound healing migration (ARPE-19; migration), and (RF/6A; angiogenesis) assays were conducted. The safety of MS intravitreal injection was assessed using hematoxylin and eosin, neuronal nuclei (NeuN) immunolabeling, and TUNEL assays, and RGC in vitro survival was analyzed. MSs delivered GDNF and co-delivered GDNF/BDNF in a sustained manner over 77 days. The BDNF/GDNF combination increased RPE cell migration, whereas no effect was observed on RF/6A. MSs did not alter cell viability, apoptosis was absent in vitro, and RGCs survived in vitro for seven weeks. In mice, retinal toxicity and apoptosis was absent in histologic sections. This delivery strategy could be useful as a potential co-therapy in retinal degenerations and glaucoma, in line with future personalized long-term intravitreal treatment as different amounts (doses) of microparticles can be administered according to patients’ needs.

Design and applications of protein delivery systems in nanomedicine and tissue engineering

Proteins are biological macromolecules involved in a wide range of biological functions, which makes them very appealing as therapeutics agents. Indeed, compared to small molecule drugs, their endogenous nature ensures their biocompatibility and biodegradability, they can be used in a large range of applications and present a higher specificity and activity. However, they suffer from unfolding, enzymatic degradation, short half-life and poor membrane permeability. To overcome such drawbacks, the development of protein delivery systems to protect, carry and deliver them in a controlled way have emerged importantly these last years. In this review, the formulation of a wide panel of protein delivery systems either in the form of polymer or inorganic nanoengineered colloids and scaffolds are presented and the protein loading and release mechanisms are addressed. A section is also dedicated to the detection of proteins and the characterization methods of their release. Then, the main protein delivery systems developed these last three years for anticancer, tissue engineering or diabetes applications are presented, as well as the major in vivo models used to test them. The last part of this review aims at presenting the perspectives of the field such as the use of protein-rich material or the sequestration of proteins. This part will also deal with less common applications and gene therapy as an indirect method to deliver protein.

Design of biodegradable bi-compartmental microneedles for the stabilization and the controlled release of the labile molecule collagenase for skin healthcare

Polymeric microneedles (MNs) have emerged as a novel class of drug delivery system thanks to their ability in penetrating the skin with no pain, encapsulate active proteins and in particular, proposed bicompartimental MNs can tune protein release.

Challenges and opportunities in the delivery of cancer therapeutics: update on recent progress

Global cancer prevalence has continuously increased in the last decades despite substantial progress achieved for patient care. Cancer is no longer recognized as a singular disease but as a plurality of different ones, leading to the important choice of the drug administration route and promoting the development of novel drug-delivery systems (DDS). Due to their structural diversity, therapeutic cancer drugs present specific challenges in physicochemical properties that can adversely affect their efficacy and toxicity profile. These challenges are addressed by innovative DDS to improve bioavailability, pharmacokinetics and biodistribution profiles. Here, we define the drug delivery challenges related to oral, intravenous, subcutaneous or alternative routes of administration, and review innovative DDS, marketed or in development, that answer those challenges.

Clinically established biodegradable long acting injectables: An industry perspective

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

Biopolymeric Coacervate Microvectors for the Delivery of Functional Proteins to Cells

The extent to which biologic payloads can be effectively delivered to cells is a limiting factor in the development of new therapies. Limitations arise from the lack of pharmacokinetic stability of biologics in vivo. Encapsulating biologics in a protective delivery vector has the potential to improve delivery profile and enhance performance. Coacervate microdroplets are developed as cell-mimetic materials with established potential for the stabilization of biological molecules, such as proteins and nucleic acids. Here, the development of biodegradable coacervate microvectors (comprising synthetically modified amylose polymers) is presented, for the delivery of biologic payloads to cells. Amylose-based coacervate microdroplets are stable under physiological conditions (e.g., temperature and ionic strength), are noncytotoxic owing to their biopolymeric structure, spontaneously interacted with the cell membrane, and are able to deliver and release proteinaceous payloads beyond the plasma membrane. In particular, myoglobin, an oxygen storage and antioxidant protein, is successfully delivered into human mesenchymal stem cells (hMSCs) within 24 h. Furthermore, coacervate microvectors are implemented for the delivery of human bone morphogenetic protein 2 growth factor, inducing differentiation of hMSCs into osteoprogenitor cells. This study demonstrates the potential of coacervate microdroplets as delivery microvectors for biomedical research and the development of new therapies.

Functionalized hydrogel microparticles prepared by microfluidics and their interaction with tumour marker carbonic anhydrase IX

Microfluidics allows precise control of the synthesis of microparticles for specific applications, where size and morphology play an important role. In this work, we have introduced microfluidic chip design with dedicated extraction and gelation sections allowing to prepare hydrogel particles in the size range of a red blood cell. The influence of the extractive channel size, alginate concentration and type of storage media on the final size of the prepared alginate microparticles has been discussed. The second part of the work is dedicated to the surface modification of prepared particles using chitosan, pHPMA and the monoclonal antibody molecule, IgG M75. The specific interaction of the antibody molecule with an antigen domain of carbonic anhydrase IX, the transmembrane tumour protein associated with several types of cancer, is demonstrated by fluorescence imaging and compared to an isotypic antibody molecule.

NMR studies of materials loaded into porous-wall hollow glass microspheres

Porous-wall hollow glass microspheres (PWHGMs) are a form of glass materials that consist of 1-μm-thick porous silica shells, 20-100 μm in diameter, with a hollow cavity in the center. Utilizing the central cavity for material storage and the porous walls for controlled release is a unique combination that renders PWHGMs a superior vehicle for targeted drug delivery. In this study, loaded PWHGMs were characterized for the first time employing proton nuclear magnetic resonance (¹H NMR) spectroscopy. A vacuum-based loading system was developed to load PWHGMs with various liquid materials followed by a washing procedure that uses solvents immiscible with the loaded materials. Immiscible binary model systems (chloroform/water, n-dodecane/water), as well as the hydrolysis reaction of isopropyl acetate, were investigated to obtain ¹H NMR evidence of loading materials into PWHGMs and their subsequent release to the surrounding solutions. The unique ¹H NMR peak shapes and relative integrals of the materials loaded in PWHGMs were distinguishable from those of the same materials in the surrounding solutions. Encounters of isopropyl acetate contained in the PWHGMs with acid protons from concentrated H₂SO₄ added to the surrounding solution become evident by the formation of the reaction product isopropanol. PWHGMs loaded with H₂O and suspended in D₂O were used to obtain quantitative release kinetics of H₂O-loaded PWHGMs. A five-parameter double-exponential curve fit of experimental ¹H NMR signal intensities as a function of time indicated two release rates for H₂O from H₂O-loaded PWHGMs suspended in D₂O with one time constant of 18-20 min and another one of 160 min. The two disparate release-rate time constants are consistent with loaded PWHGMs with breached and unbreached porous walls. The results demonstrate that ¹H NMR spectroscopy is particularly useful for investigating formulations and applications of PWHGMs in targeted drug delivery.

Exploring Endolysin-Loaded Alginate-Chitosan Nanoparticles as Future Remedy for Staphylococcal Infections

Endolysins are a novel class of antibacterials with proven efficacy in combating various bacterial infections, in vitro and in vivo. LysMR-5, an endolysin derived from phage MR-5, demonstrated high lytic activity in our laboratory against multidrug-resistant S. aureus (MRSA) and S. epidermidis strains. However, endolysin and proteins in general are associated with instability and short in vivo half-life, consequently limiting their usage as pharmaceutical preparation to treat bacterial infections. Nanoencapsulation of endolysins could help to achieve better therapeutic outcome, by protecting the proteins from degradation, providing sustained release, thus could increase their stability, shelf life, and therapeutic efficacy. Hence, in this study, the feasibility of alginate-chitosan nanoparticles (Alg-Chi NPs) to serve as drug delivery platform for LysMR-5 was evaluated. LysMR-5-loaded nanoparticles were prepared by calcium ion-induced pre-gelation of alginate core and its complexation with chitosan. The formation of nanoparticles was confirmed on the basis of DLS, zeta potential, and electron microscopy imaging. The LysMR-5-loaded nanoparticles presented a hydrodynamic diameter of 276.5 ± 42, a PDI of 0.342 ± 0.02, a zeta potential - 25 mV, and an entrapment efficiency of 62 ± 3.1%. The potential ionic interaction between alginate, chitosan, and LysMR-5 was investigated by FT-IR and SEM-EDX analysis. Using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), nano-sized particles with characteristic morphology were seen. Different antibacterial assays and SDS-PAGE analysis showed no change in endolysin's structural integrity and bioactivity after entrapment. A direct antibacterial effect of blank Alg-Chi Nps, showing enhanced bactericidal activity upon LysMR-5 loading, was observed against S. aureus. At physiological pH (7.2), the release profile of LysMR-5 from Alg-Chi NPs showed a biphasic release and followed a non-Fickian release mechanism. The biocompatible nature as revealed by cytocompatibility and hemocompatibility studies endorsed their use as drug delivery system for in vivo studies. Collectively, these results demonstrate the potential of Alg-Chi NPs as nano-delivery vehicle for endolysin LysMR-5 and other therapeutic proteins for their use in various biomedical applications.

Microfluidic fabrication of microcarriers with sequential delivery of VEGF and BMP-2 for bone regeneration

Wound instability and poor functional vascularization in bone tissue engineering lead to lack of tissue integration and ultimate failure of engineered grafts. In order to harness the regenerative potential of growth factors and stimulate bone healing, present study aims to design multifunctional cell therapy microcarriers with the capability of sequential delivery of essential growth factors, bone morphogenetic protein 2 (BMP-2) and vascular endothelial growth factor (VEGF). An on-chip double emulsion method was implemented to generate monodisperse VEGF encapsulated microcarriers. Bio-inspired poly(3,4-dihydroxyphenethylamine) (PDA) was then functionalized to the microcarriers surface for BMP-2 conjugation. The microcarriers were seeded with mesenchymal stem cells (MSCs) using a dynamic culture technique for cells expansion. Finally, the microcarriers were incorporated into an injectable alginate-RGD hydrogel laden with endothelial cells (ECs) for further analysis. The DNA and calcium content, as well as ALP activity of the construct were analyzed. The confocal fluorescent microscopy was employed to monitor the MSCs and tunneling structure of ECs. Eventually, the capability of developed microcarriers for bone tissue formation was examined in vivo. Microfluidic platform generated monodisperse VEGF-loaded PLGA microcarriers with size-dependent release patterns. Microcarriers generated with the on-chip technique showed more sustained VEGF release profiles compared to the conventional bulk mixing method. The PDA functionalization of microcarriers surface not only provided immobilization of BMP-2 with prolonged bioavailability, but also enhanced the attachment and proliferation of MSCs. Dynamic culturing of microcarriers showcased their great potential to boost MSCs population required for stem cell therapy of bone defects. ALP activity and calcium content analysis of MSCs-laden microcarriers loaded into injectable hydrogels revealed their capability of tunneling formation, vascular cell growth and osteogenic differentiation. The in vivo histology and real-time polymerase chain reaction analysis revealed that transplantation of MSC-laden microcarriers supports ectopic bone formation in the rat model. The presented approach to design bioactive microcarriers offer sustained sequential delivery of bone ECM chemical cues and offer an ideal stabilized 3D microenvironment for patient-specific cell therapy applications. The proposed methodology is readily expandable to integrate other cells and cytokines in a tuned spatiotemporal manner for personalized regenerative medicine.

Biocompatibility and bioactivity of an FGF-loaded microsphere-based bilayer delivery system

Many drug delivery systems rely on degradation or dissolution of the carrier material to regulate release. In cases where mechanical support is required during regeneration, this necessitates composite systems in which the mechanics of the implant are decoupled from the drug release profile. To address this need, we developed a system in which microspheres (MS) were sequestered in a defined location between two nanofibrous layers. This bilayer delivery system (BiLDS) enables simultaneous structural support and decoupled release profiles. To test this new system, PLGA (poly-lactide-co-glycolic acid) microspheres were prepared using a water-in-oil-in-water (w/o/w) emulsion technique and incorporated Alexa Fluor-tagged bovine serum albumin (BSA) and basic fibroblast growth factor (bFGF). These MS were secured in a defined pocket between two polycaprolactone (PCL) nanofibrous scaffolds, where the layered scaffolds provide a template for new tissue formation while enabling independent and local release from the co-delivered MS. Scanning electron microscopy (SEM) images showed that the assembled BiLDS could localize and retain MS in the central pocket that was surrounded by a continuous seal formed along the margin. Cell viability and proliferation assays showed enhanced cell activity when exposed to BiLDS containing Alexa Fluor-BSA/bFGF-loaded MS, both in vitro and in vivo. MS delivered via the BiLDS system persisted in a localized area after subcutaneous implantation for at least 4 weeks, and bFGF release increased colonization of the implant. These data establish the BiLDS technology as a sustained in vivo drug delivery platform that can localize protein and other growth factor release to a surgical site while providing a structural template for new tissue formation. STATEMENT OF SIGNIFICANCE: Localized and controlled delivery systems for the sustained release of drugs are essential. Many strategies have been developed for this purpose, but most rely on degradation (and loss of material properties) for delivery. Here, we developed a bilayer delivery system (BiLDS) that decouples the physical properties of a scaffold from its delivery kinetics. For this, biodegradable PLGA microspheres were sequestered within a central pocket of a slowly degrading nanofibrous bilayer. Using this device, we show enhanced cell activity with FGF delivery from the BiLDS both in vitro and in vivo. These data support that BiLDS can localize sustained protein and biofactor delivery to a surgical site while also serving as a mechanical scaffold for tissue repair and regeneration.

Development of a Negative-Biased Zwitterionic Polypeptide-Based Nanodrug Vehicle for pH-Triggered Cellular Uptake and Accelerated Drug Release

Albumin mimics could be an attractive platform for nanodrug carriers through systematic administration because of high safety and plentiful properties to be adjusted for a high drug efficacy, such as pH-triggered targeting cellular uptake and drug release. In this work, negative-biased zwitterionic nanodrug carriers based on zwitterionic polypeptide chains that mimic albumin were prepared, which have an outermost layer of zwitterionic glutamic acid (E) and lysine (K) pairs with a small amount of aspartic acid (D) to adjust the overall ζ potential. On the other hand, doxorubicin (Dox) was encapsulated in a hydrophobic core by 11-maleimidoundecanoic acid covalently linked with additional cysteine (C) residues on the polypeptide. The results show that the negative-biased zwitterionic nanodrug carriers can sensitively enhance the cellular uptake in responding to a pH change from 7.4 to 6.7 without reversing the ζ potential to a positive charge, leading to accelerating the Dox release rate in a slightly acidic environment through the polypeptide secondary structure change. Moreover, the anionic nanodrug carrier can also be easily enzymatically digested by trypsin for quick drug release. In short, this negative-biased zwitterionic nanodrug delivery vector could be an ideal candidate for a safer tumor inhibition with a high efficacy than conventional synthetic polymer-based ones.