The hydrogel template method for fabrication of homogeneous nano/microparticles

PLGA-based long-acting injectable (LAI) formulations

Long-acting injectable (LAI) formulations, which deliver drugs over weeks or months, have been in use for more than three decades. Most clinically approved LAI products are formulated using poly(lactide-co-glycolide) (PLGA) polymers. Historically, the development of PLGA-based LAI formulations has relied predominantly on trial-and-error methods, primarily due to a limited understanding of the complex factors involved in LAI formulations and insufficient analytical techniques available for characterizing individual PLGA polymers of the prepared formulations. This article offers a personal perspective on recent advancements in characterization methods for PLGA polymers within final formulations, i.e., products, as well as enhanced insights into the drug release mechanisms associated with LAI products. With a deeper understanding of PLGA polymer properties and drug release mechanisms, the formulation development process can transition from traditional trial-and-error practices to a more systematic Quality by Design (QbD) approach. Additionally, this article explores the emerging role of artificial intelligence (AI) in formulation science and its potential, when applied carefully, to enhance the future development of PLGA-based LAI formulations.

Fabrication of uniform biodegradable microcages with predesigned shape printed from microarrays for sustained release of small hydrophilic molecules

Drug delivery vehicles have aroused increasing attention over the years due to their ability to protect and control the release of encapsulated cargo. However, several challenges significantly limit their wide applications including poor size distribution, uncontrollable size and shape, and leakage of loaded small hydrophilic cargos. This work introduces a novel and scalable microarray-based printing technique for preparing uniform biodegradable "microcages" with predesigned shapes for encapsulating and controlling the release of small hydrophilic molecules. The drugs encapsulated in the microcage are centrally located within solid microparticles without being exposed to the surface or dispersed throughout the polymer matrix. Here, 5(6)-carboxyfluorescein (CF) as a small and hydrophilic model drug are successfully loaded into polylactide acid (PLA) microcages with the dry loading method. Additionally, blending polycaprolactone (PCL) with PLA increases the permeability of the microcage polymer shells for controlled release. A higher PCL content results in a faster release rate of the encapsulated drug. Approximately 28 pg of CF particles can be encapsulated within individual microcages. This microcage printing technique provides a novel, scalable method for producing uniform biodegradable microcages, extending microprinting beyond microfilms and microparticles. A unique dry loading approach, independent of drug solubility, further broadens its utility for diverse biomedical applications.

Ocular drug delivery systems based on nanotechnology: a comprehensive review for the treatment of eye diseases

Ocular drug delivery is a significant challenge due to the intricate anatomy of the eye and the various physiological barriers. Conventional therapeutic approaches, while effective to some extent, often fall short in effectively targeting ocular diseases, resulting in suboptimal therapeutic outcomes due to factors such as poor ocular bioavailability, frequent dosing requirements, systemic side effects, and limited penetration through ocular barriers. This review elucidates the eye's intricate anatomy and physiology, prevalent ocular diseases, traditional therapeutic modalities, and the inherent pharmacokinetic and pharmacodynamic limitations associated with these modalities. Subsequently, it delves into nanotechnology-based solutions, presenting breakthroughs in nanoformulations such as nanocrystals, liposomes, dendrimers, and nanoemulsions that have demonstrated enhanced drug stability, controlled release, and deeper ocular penetration. Additionally, it explores a range of nanosized carriers, including nano-structured lipid carriers, hydrogels, nanogels, nanoenzymes, microparticles, conjugates, exosomes, nanosuspensions, viral vectors, and polymeric nanoparticles, and their applications. Unique insights include emerging innovations such as nanowafers and transcorneal iontophoresis, which indicate paradigm shifts in non-invasive ocular drug delivery. Furthermore, it sheds light on the advantages and limitations of these nanotechnology-based platforms in addressing the challenges of ocular drug delivery. Though nano-based drug delivery systems are drawing increasing attention due to their potential to enhance bioavailability and therapeutic efficacy, the review ends up emphasizing the imperative need for further research to drive innovation and improve patient outcomes in ophthalmology.

Cardiac Matrix-Derived Granular Hydrogel Enhances Cell Function in 3D Culture

Hydrogels derived from decellularized porcine myocardial matrix have demonstrated significant potential as therapeutic delivery platforms for promoting cardiac repair after injury. Our previous study developed a fibrin-enriched cardiac matrix hydrogel to enhance its angiogenic capacities. However, the bulk hydrogel structure may limit their full potential in cell delivery. Recently, granular hydrogels have emerged as a promising class of biomaterials, offering unique features such as a highly interconnected porous structure that facilitates nutrient diffusion and enhances cell viability. Several techniques have been developed for fabricating various types of granular hydrogels, among which extrusion fragmentation is particularly appealing due to its adaptability to many types of hydrogels, low cost, and high scalability. In this study, we first confirmed the effects of the bulk cardiac matrix hydrogel on the viability of encapsulated human umbilical vein endothelial cells and human mesenchymal stem cells. We then tested the feasibility of producing granular hydrogels from both cardiac matrix and fibrin-enriched cardiac matrix through cellular cross-linking of microgels fabricated by extrusion fragmentation. Afterward, we examined the roles of the produced granular hydrogels in the embedded cells and cell spheroids. Our in vitro data demonstrate that cardiac matrix-derived granular hydrogels support optimal viability of encapsulated cells and promote sprouting of human mesenchymal stem cell spheroids. Additionally, granular hydrogel derived from fibrin-enriched cardiac matrix accelerates angiogenic sprouting of embedded human mesenchymal stem cell spheroids. The results obtained from this study lay an important foundation for the future exploration of using cardiac matrix-derived granular hydrogels for cardiac cell therapy.

Effective intravitreal gene delivery to retinal pigment epithelium with hyaluronic acid nanospheres

Inherited retinal degeneration (IRD) can cause a wide range of different forms of vision loss and blindness, and in spite of extensive advancements in gene therapy research, therapeutic approaches for targeting IRDs are still lacking. We have recently developed an approach for the intravitreal co-delivery of hyaluronic-acid nanospheres (HA-NSs) with sulfotyrosine (ST), effectively reaching the outer retina from the vitreal cavity. Here, our goal was to understand whether DNA-filled HA-NSs could generate gene expression in the outer retina. TxRed-labeled HA-NSs were compacted with plasmid DNA carrying a GFP reporter gene and intravitreally injected into the mouse retina. Follow-up at 4 weeks showed widespread gene expression in the outer retina and reduced, albeit present, expression at 8 weeks post-injection. Further analysis revealed this expression to be largely localized to the retinal pigment epithelium (RPE). These data show that intravitreal delivery of HA-NSs is a promising non-viral platform for the delivery of therapeutic genes and can generate pan-tissue, persistent gene expression in the RPE.

Hydrogel Microparticles for Bone Regeneration

Hydrogel microparticles (HMPs) stand out as promising entities in the realm of bone tissue regeneration, primarily due to their versatile capabilities in delivering cells and bioactive molecules/drugs. Their significance is underscored by distinct attributes such as injectability, biodegradability, high porosity, and mechanical tunability. These characteristics play a pivotal role in fostering vasculature formation, facilitating mineral deposition, and contributing to the overall regeneration of bone tissue. Fabricated through diverse techniques (batch emulsion, microfluidics, lithography, and electrohydrodynamic spraying), HMPs exhibit multifunctionality, serving as vehicles for drug and cell delivery, providing structural scaffolding, and functioning as bioinks for advanced 3D-printing applications. Distinguishing themselves from other scaffolds like bulk hydrogels, cryogels, foams, meshes, and fibers, HMPs provide a higher surface-area-to-volume ratio, promoting improved interactions with the surrounding tissues and facilitating the efficient delivery of cells and bioactive molecules. Notably, their minimally invasive injectability and modular properties, offering various designs and configurations, contribute to their attractiveness for biomedical applications. This comprehensive review aims to delve into the progressive advancements in HMPs, specifically for bone regeneration. The exploration encompasses synthesis and functionalization techniques, providing an understanding of their diverse applications, as documented in the existing literature. The overarching goal is to shed light on the advantages and potential of HMPs within the field of engineering bone tissue.

In situ PEGylation of CAR T cells alleviates cytokine release syndrome and neurotoxicity

Chimeric antigen receptor T (CAR T) cell immunotherapy is successful at treating many cancers. However, it often induces life-threatening cytokine release syndrome (CRS) and neurotoxicity. Here, we show that in situ conjugation of polyethylene glycol (PEG) to the surface of CAR T cells ('PEGylation') creates a polymeric spacer that blocks cell-to-cell interactions between CAR T cells, tumour cells and monocytes. Such blockage hinders intensive tumour lysing and monocyte activation by CAR T cells and, consequently, decreases the secretion of toxic cytokines and alleviates CRS-related symptoms. Over time, the slow expansion of CAR T cells decreases PEG surface density and restores CAR T cell-tumour-cell interactions to induce potent tumour killing. This occurs before the restoration of CAR T cell-monocyte interactions, opening a therapeutic window for tumour killing by CAR T cells before monocyte overactivation. Lethal neurotoxicity is also lower when compared with treatment with the therapeutic antibody tocilizumab, demonstrating that in situ PEGylation of CAR T cells provides a materials-based strategy for safer cellular immunotherapy.

The application of electrosprayed minocycline-loaded PLGA microparticles for the treatment of glioblastoma

The survival of patients with glioblastoma multiforme (GBM), the most common and invasive form of malignant brain tumors, remains poor despite advances in current treatment methods including surgery, radiotherapy, and chemotherapy. Minocycline is a semi-synthetic tetracycline derivative that has been widely used as an antibiotic and more recently, it has been utilized as an antiangiogenic factor to inhibit tumorigenesis. The objective of this study was to investigate the utilization of electrospraying process to fabricate minocycline-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles with high drug loading and loading efficiency and to evaluate their ability to induce cell toxicity in human glioblastoma (i.e., U87-MG) cells. The results from this study demonstrated that solvent mixture of dicholoromethane (DCM) and methanol is the optimal solvent combination for minocycline and larger amount of methanol (i.e., 70:30) resulted in a higher drug loading. All three solvent ratios of DCM:methanol tested produced microparticles that were both spherical and smooth, all in the micron size range. The electrosprayed microparticles were able to elicit a cytotoxic response in U87-MG glioblastoma cells at a lower concentration of drug compared to the free drug. This work provides proof of concept to the hypothesis that electrosprayed minocycline-loaded PLGA microparticles can be a promising agent for the treatment of GBM and could have potential application for cancer therapies.

Recent Advances in Biodegradable and Biocompatible Synthetic Polymers Used in Skin Wound Healing

The treatment of skin wounds caused by trauma and pathophysiological disorders has been a growing healthcare challenge, posing a great economic burden worldwide. The use of appropriate wound dressings can help to facilitate the repair and healing rate of defective skin. Natural polymer biomaterials such as collagen and hyaluronic acid with excellent biocompatibility have been shown to promote wound healing and the restoration of skin. However, the low mechanical properties and fast degradation rate have limited their applications. Skin wound dressings based on biodegradable and biocompatible synthetic polymers can not only overcome the shortcomings of natural polymer biomaterials but also possess favorable properties for applications in the treatment of skin wounds. Herein, we listed several biodegradable and biocompatible synthetic polymers used as wound dressing materials, such as PVA, PCL, PLA, PLGA, PU, and PEO/PEG, focusing on their composition, fabrication techniques, and functions promoting wound healing. Additionally, the future development prospects of synthetic biodegradable polymer-based wound dressings are put forward. Our review aims to provide new insights for the further development of wound dressings using synthetic biodegradable polymers.

Chitosan-Based Hydrogel in the Management of Dermal Infections: A Review

The main objective of this review is to provide a comprehensive overview of the current evidence regarding the use of chitosan-based hydrogels to manage skin infections. Chitosan, a naturally occurring polysaccharide derived from chitin, possesses inherent antimicrobial properties, making it a promising candidate for treating various dermal infections. This review follows a systematic approach to analyze relevant studies that have investigated the effectiveness of chitosan-based hydrogels in the context of dermal infections. By examining the available evidence, this review aims to evaluate these hydrogels' overall efficacy, safety, and potential applications for managing dermal infections. This review's primary focus is to gather and analyze data from different recent studies about chitosan-based hydrogels combating dermal infections; this includes assessing their ability to inhibit the growth of microorganisms and reduce infection-related symptoms. Furthermore, this review also considers the safety profile of chitosan-based hydrogels, examining any potential adverse effects associated with their use. This evaluation is crucial to ensure that these hydrogels can be safely utilized in the management of dermal infections without causing harm to patients. The review aims to provide healthcare professionals and researchers with a comprehensive understanding of the current evidence regarding the use of chitosan-based hydrogels for dermal infection management. The findings from this review can contribute to informed decision-making and the development of potential treatment strategies in this field.

Multifunctional Self-Assembled Peptide Hydrogels for Biomedical Applications

Self-assembly is a growth mechanism in nature to apply local interactions forming a minimum energy structure. Currently, self-assembled materials are considered for biomedical applications due to their pleasant features, including scalability, versatility, simplicity, and inexpensiveness. Self-assembled peptides can be applied to design and fabricate different structures, such as micelles, hydrogels, and vesicles, by diverse physical interactions between specific building blocks. Among them, bioactivity, biocompatibility, and biodegradability of peptide hydrogels have introduced them as versatile platforms in biomedical applications, such as drug delivery, tissue engineering, biosensing, and treating different diseases. Moreover, peptides are capable of mimicking the microenvironment of natural tissues and responding to internal and external stimuli for triggered drug release. In the current review, the unique characteristics of peptide hydrogels and recent advances in their design, fabrication, as well as chemical, physical, and biological properties are presented. Additionally, recent developments of these biomaterials are discussed with a particular focus on their biomedical applications in targeted drug delivery and gene delivery, stem cell therapy, cancer therapy and immune regulation, bioimaging, and regenerative medicine.

A decade of developing applications exploiting the properties of polyelectrolyte multilayer capsules

Transferring the layer-by-layer (LbL) coating approach from planar surfaces to spherical templates and subsequently dissolving these templates leads to the fabrication of polyelectrolyte multilayer capsules. The versatility of the coatings of capsules and their flexibility upon bringing in virtually any material into the coatings has quickly drawn substantial attention. Here, we provide an overview of the main developments in this field, highlighting the trends in the last decade. In the beginning, various methods of encapsulation and release are discussed followed by a broad range of applications, which were developed and explored. We also outline the current trends, where the range of applications is continuing to grow, including addition of whole new and different application areas.

Shape-specific microfabricated particles for biomedical applications: a review

The storied history of controlled the release systems has evolved over time; from degradable drug-loaded sutures to monolithic zero-ordered release devices and nano-sized drug delivery formulations. Scientists have tuned the physico-chemical properties of these drug carriers to optimize their performance in biomedical/pharmaceutical applications. In particular, particle drug delivery systems at the micron size regime have been used since the 1980s. Recent advances in micro and nanofabrication techniques have enabled precise control of particle size and geometry-here we review the utility of microplates and discoidal polymeric particles for a range of pharmaceutical applications. Microplates are defined as micrometer scale polymeric local depot devices in cuboid form, while discoidal polymeric nanoconstructs are disk-shaped polymeric particles having a cross-sectional diameter in the micrometer range and a thickness in the hundreds of nanometer range. These versatile particles can be used to treat several pathologies such as cancer, inflammatory diseases and vascular diseases, by leveraging their size, shape, physical properties (e.g., stiffness), and component materials, to tune their functionality. This review highlights design and fabrication strategies for these particles, discusses their applications, and elaborates on emerging trends for their use in formulations.

Co-Injection of Sulfotyrosine Facilitates Retinal Uptake of Hyaluronic Acid Nanospheres Following Intravitreal Injection

Gene and drug delivery to the retina is a critical therapeutic goal. While the majority of inherited forms of retinal degeneration affect the outer retina, specifically the photoreceptors and retinal pigment epithelium, effective targeted delivery to this region requires invasive subretinal delivery. Our goal in this work was to evaluate two innovative approaches for increasing both the persistence of delivered nanospheres and their penetration into the outer retina while using the much less invasive intravitreal delivery method. We formulated novel hyaluronic acid nanospheres (HA-NS, 250 nm and 500 nm in diameter) conjugated to fluorescent reporters and delivered them intravitreally to the adult Balb/C mouse retina. They exhibited persistence in the vitreous and along the inner limiting membrane (ILM) for up to 30 days (longest timepoint examined) but little retinal penetration. We thus evaluated the ability of the small molecule, sulfotyrosine, to disrupt the ILM, and found that 3.2 µg/µL sulfotyrosine led to significant improvement in delivery to the outer retina following intravitreal injections without causing retinal inflammation, degeneration, or loss of function. Co-delivery of sulfotyrosine and HA-NS led to robust improvements in penetration of HA-NS into the retina and accumulation along the interface between the photoreceptors and the retinal pigment epithelium. These exciting findings suggest that sulfotyrosine and HA-NS may be an effective strategy for outer retinal targeting after intravitreal injection.

Recent advances in ocular drug delivery systems and targeting VEGF receptors for management of ocular angiogenesis: A comprehensive review

Background

Angiogenic ocular diseases address the main source of vision impairment or irreversible vision loss. The angiogenesis process depends on the balance between the pro-angiogenic and anti-angiogenic factors. An imbalance between these factors leads to pathological conditions in the body. The vascular endothelial growth factor is the main cause of pathological conditions in the ocular region. Intravitreal injections of anti-angiogenic drugs are selective, safe, specific and revolutionized treatment for ocular angiogenesis. But intravitreal injections are invasive techniques with other severe complications. The area of targeting vascular endothelial growth factor receptors progresses with novel approaches and therapeutically based hope for best clinical outcomes for patients through the developments in anti-angiogenic therapy.

Main text

The present review article gathers prior knowledge about the vascular endothelial growth factor and associated receptors with other angiogenic and anti-angiogenic factors involved in ocular angiogenesis. A focus on the brief mechanism of vascular endothelial growth factor inhibitors in the treatment of ocular angiogenesis is elaborated. The review also covers various recent novel approaches available for ocular drug delivery by comprising a substantial amount of research works. Besides this, we have also discussed in detail the adoption of nanotechnology-based drug delivery systems in ocular angiogenesis by comprising literature having recent advancements. The clinical applications of nanotechnology in terms of ocular drug delivery, risk analysis and future perspectives relating to the treatment approaches for ocular angiogenesis have also been presented.

Conclusion

The novel ocular drug delivery systems involving nanotechnologies are of great importance in the ophthalmological sector to overcome traditional treatments with many drawbacks. This article gives a detailed insight into the various approaches that are currently available to be a road map for future research in the field of ocular angiogenesis disease management.

Emerging Nano-Formulations and Nanomedicines Applications for Ocular Drug Delivery

Ocular diseases can deteriorate vision to the point of blindness and thus can have a major impact on the daily life of an individual. Conventional therapies are unable to provide absolute therapy for all ocular diseases due to the several limitations during drug delivery across the blood-retinal barrier, making it a major clinical challenge. With recent developments, the vast number of publications undergird the need for nanotechnology-based drug delivery systems in treating ocular diseases. The tool of nanotechnology provides several essential advantages, including sustained drug release and specific tissue targeting. Additionally, comprehensive in vitro and in vivo studies have suggested a better uptake of nanoparticles across ocular barriers. Nanoparticles can overcome the blood-retinal barrier and consequently increase ocular penetration and improve the bioavailability of the drug. In this review, we aim to summarize the development of organic and inorganic nanoparticles for ophthalmic applications. We highlight the potential nanoformulations in clinical trials as well as the products that have become a commercial reality.

Highly efficient and cheap treatment of dye by graphene-doped TiO2 microspheres

Highly efficient dye wastewater treatment by photocatalytic catalysis commonly requires expensive catalysts, long degradation time and a complicated procedure. Here, we for the first time prepared cheap graphene-doped titanium dioxide microspheres with a simple procedure to degrade dye with high efficiency. When the catalyst concentration was 0.2 g·L^-1, the photocatalysis degradation extent of methylene blue solution, methylene green solution and 1,9-dimethyl methylene blue solution reached 96.4, 85.9 and 98.7%, respectively. The results showed that the degradation reactions accorded with the Langmuir-Hinshelwood model, and the photocatalytic reactions belonged to a first-order reaction in the primary stage. Furthermore, different photocatalytic degradation mechanisms were proposed, which have not been found in other literature. This work opened a new route for simple preparation of cheap microspheres in photocatalytic dye wastewater treatment with high efficiency.

Electrification at water-hydrophobe interfaces

The mechanisms leading to the electrification of water when it comes in contact with hydrophobic surfaces remains a research frontier in chemical science. A clear understanding of these mechanisms could, for instance, aid the rational design of triboelectric generators and micro- and nano-fluidic devices. Here, we investigate the origins of the excess positive charges incurred on water droplets that are dispensed from capillaries made of polypropylene, perfluorodecyltrichlorosilane-coated glass, and polytetrafluoroethylene. Results demonstrate that the magnitude and sign of electrical charges vary depending on: the hydrophobicity/hydrophilicity of the capillary; the presence/absence of a water reservoir inside the capillary; the chemical and physical properties of aqueous solutions such as pH, ionic strength, dielectric constant and dissolved CO2 content; and environmental conditions such as relative humidity. Based on these results, we deduce that common hydrophobic materials possess surface-bound negative charge. Thus, when these surfaces are submerged in water, hydrated cations form an electrical double layer. Furthermore, we demonstrate that the primary role of hydrophobicity is to facilitate water-substrate separation without leaving a significant amount of liquid behind. These results advance the fundamental understanding of water-hydrophobe interfaces and should translate into superior materials and technologies for energy transduction, electrowetting, and separation processes, among others.

Nanocarriers for ocular drug delivery: current status and translational opportunity

Ocular diseases have a significant effect on vision and quality of life. Drug delivery to ocular tissues is a challenge to formulation scientists. The major barriers to delivering drugs to the anterior and posterior segments include physiological barriers (nasolacrimal drainage, blinking), anatomical barriers (static and dynamic), efflux pumps and metabolic barriers. The static barriers comprise the different layers of the cornea, sclera, and blood-aqueous barriers whereas dynamic barriers involve conjunctival blood flow, lymphatic clearance and tear drainage. The tight junctions of the blood-retinal barrier (BRB) restrict systemically administered drugs from entering the retina. Nanocarriers have been found to be effective at overcoming the issues associated with conventional ophthalmic dosage forms. Various nanocarriers, including nanodispersion systems, nanomicelles, lipidic nanocarriers, polymeric nanoparticles, liposomes, niosomes, and dendrimers, have been investigated for improved permeation and effective targeted drug delivery to various ophthalmic sites. In this review, various nanomedicines and their application for ophthalmic delivery of therapeutics are discussed. Additionally, scale-up and clinical status are also addressed to understand the current scenario for ophthalmic drug delivery.

Degassed micromolding lithography for rapid fabrication of anisotropic hydrogel microparticles with high-resolution and high uniformity

Replica molding techniques, which are used to synthesize microparticles inside anisotropic micromolds, have been developed to enable the mass production of hydrogel particles. However, these techniques are limited in their ability to synthesize only a narrow range of particle compositions and shapes because of the difficulty in loading precursors into the micromolds as well as the low particle homogeneity due to the uneven evaporation of the precursors. Herein, we describe a simple yet powerful technique, called degassed micromolding lithography, which can load precursors within 1 min regardless of the wettability. This technique is based on the gas-solubility of a degassed micromold that acts as a suction pump to completely fill the mold by drawing precursor liquids in. The semi-closed system within the micromold prevents the uneven evaporation of the precursor, which is essential for the production of homogeneous particles. Furthermore, controlled uniformity of the hydrogel microparticles (C.V. < 2%) can be achieved by engineering the design of the micromold array.

Therapeutic implications of nanomedicine for ocular drug delivery

Delivering therapeutics to the eye is challenging on multiple levels: rapid clearance of eyedrops from the ocular surface requires frequent instillation, which is difficult for patients; transport of drugs across the blood-retinal barrier when drugs are administered systemically, and the cornea when drugs are administered topically, is difficult to achieve; limited drug penetration to the back of the eye owing to the cornea, conjunctiva, sclera and vitreous barriers. Nanomedicine offers many advantages over conventional ophthalmic medications for effective ocular drug delivery because nanomedicine can increase the therapeutic index by overcoming ocular barriers, improving drug-release profiles and reducing potential drug toxicity. In this review, we highlight the therapeutic implications of nanomedicine for ocular drug delivery.

Agar Hydrogel Template Synthesis of Mn₃O₄ Nanoparticles through an Ion Diffusion Method Controlled by Ion Exchange Membrane and Electrochemical Performance

A novel strategy, ion diffusion method controlled by ion exchange membrane combining with agar hydrogel template, was reported for the synthesis of Mn₃O₄ nanoparticles without any oxidizing agents. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauere-Emmette-Teller (BET) isotherm were carried out to characterize the structure, morphology, pore size and distribution and specific surface area of the as-prepared nanomaterials. It is shown that the morphology and size of Mn₃O₄ nanoparticles can be controlled by the concentration of agar hydrogel. All the specific capacitances of the Mn₃O₄ samples prepared with agar hydrogel template are much higher than that of Mn₃O₄ prepared without any template agent. The Mn₃O₄ sample prepared at 1.5 g L-1 of agar hydrogel solution exhibits a highest specific capacitance of 183.0 F g-1 at the current density of 0.5 A g-1, which is increased by 293% compared with that of Mn₃O₄ synthesized without any template agent. The results indicate that the ion diffusion method controlled by ion exchange membrane combining with agar hydrogel template is a convenient and effective approach for preparing inorganic nanomaterials.

Effects of solvent used for fabrication on drug loading and release kinetics of electrosprayed temozolomide-loaded PLGA microparticles for the treatment of glioblastoma

Glioblastoma multiforme (GBM) is the most common and invasive form of malignant brain tumors and despite advances in surgery, radiotherapy, and chemotherapy, the survival of patients with GBM still remains poor. Temozolomide (TMZ) is the chemotherapy drug that is most commonly given orally after surgical resection of these tumors. In this study, the effects of solvents (i.e., dichloromethane and acetonitrile) used for the fabrication of electrosprayed TMZ-loaded poly(lactic-co-glycolic acid) (PLGA) on drug loading, loading efficiency, drug release kinetics, surface morphology, and particle size were investigated. The results from this study demonstrated that by using a larger volume of a solvent with higher polarity (i.e., acetonitrile) which allows for a higher amount of hydrophilic TMZ to dissolve into the polymer solution, higher drug loading could be achieved. However, the particles fabricated with high amount of acetonitrile, which has a lower vapor pressure, had large pores and a smaller diameter which led to an initial burst release and high cumulative release at the end of the study. An optimal combination of the two solvents is needed to result in particles with a good amount of loading and minimal initial burst release. The electrosprayed microparticles were able to illicit a cytotoxic response in U-87 MG glioblastoma cells at a lower concentration of drug compared to the free drug. This work indicated that electrospraying is a promising method for the fabrication of TMZ-loaded PLGA microparticles for the treatment of GBM and solvent composition can be altered to control drug loading and release kinetics. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2317-2324, 2019.

Microfabricated devices for oral drug delivery

Oral administration of drugs is most convenient for patients and therefore the ultimate goal when developing new medication. The physical barriers in the body, low pH of the stomach and degradation by enzymes in the gastrointestinal tract are a few of the obstacles to succeeding with oral drug delivery. Microfabricated devices show promise to overcome some of these hindrances and thereby improve the bioavailability of drugs after oral administration. There is an increasing focus on microfabricated oral drug delivery systems, and so far there have been three main groups of designs: patch-like structures, microcontainers and microwells. Here, we review the newest development in top-down microfabricated devices for oral drug delivery with coverage of the aspects of design, choice of material and fabrication techniques. Furthermore, the drug loading techniques and methods for testing are discussed. In addition, we discuss the future perspectives for microfabricated devices.

Transcutaneously refillable, 3D-printed biopolymeric encapsulation system for the transplantation of endocrine cells

Autologous cell transplantation holds enormous promise to restore organ and tissue functions in the treatment of various pathologies including endocrine, cardiovascular, and neurological diseases among others. Even though immune rejection is circumvented with autologous transplantation, clinical adoption remains limited due to poor cell retention and survival. Cell transplant success requires homing to vascularized environment, cell engraftment and importantly, maintenance of inherent cell function. To address this need, we developed a three dimensional (3D) printed cell encapsulation device created with polylactic acid (PLA), termed neovascularized implantable cell homing and encapsulation (NICHE). In this paper, we present the development and systematic evaluation of the NICHE in vitro, and the in vivo validation with encapsulated testosterone-secreting Leydig cells in Rag1-/- castrated mice. Enhanced subcutaneous vascularization of NICHE via platelet-rich plasma (PRP) hydrogel coating and filling was demonstrated in vivo via a chorioallantoic membrane (CAM) assay as well as in mice. After establishment of a pre-vascularized bed within the NICHE, transcutaneously transplanted Leydig cells, maintained viability and robust testosterone secretion for the duration of the study. Immunohistochemical analysis revealed extensive Leydig cell colonization in the NICHE. Furthermore, transplanted cells achieved physiologic testosterone levels in castrated mice. The promising results provide a proof of concept for the NICHE as a viable platform technology for autologous cell transplantation for the treatment of a variety of diseases.

Generation of Well-Defined Micro/Nanoparticles via Advanced Manufacturing Techniques for Therapeutic Delivery

Micro/nanoparticles have great potentials in biomedical applications, especially for drug delivery. Existing studies identified that major micro/nanoparticle features including size, shape, surface property and component materials play vital roles in their in vitro and in vivo applications. However, a demanding challenge is that most conventional particle synthesis techniques such as emulsion can only generate micro/nanoparticles with a very limited number of shapes (i.e., spherical or rod shapes) and have very loose control in terms of particle sizes. We reviewed the advanced manufacturing techniques for producing micro/nanoparticles with precisely defined characteristics, emphasizing the use of these well-controlled micro/nanoparticles for drug delivery applications. Additionally, to illustrate the vital roles of particle features in therapeutic delivery, we also discussed how the above-mentioned micro/nanoparticle features impact in vitro and in vivo applications. Through this review, we highlighted the unique opportunities in generating controllable particles via advanced manufacturing techniques and the great potential of using these micro/nanoparticles for therapeutic delivery.

Hierarchical Microplates as Drug Depots with Controlled Geometry, Rigidity, and Therapeutic Efficacy

A variety of microparticles have been proposed for the sustained and localized delivery of drugs with the objective of increasing therapeutic indexes by circumventing filtering organs and biological barriers. Yet, the geometrical, mechanical, and therapeutic properties of such microparticles cannot be simultaneously and independently tailored during the fabrication process to optimize their performance. In this work, a top-down approach is employed to realize micron-sized polymeric particles, called microplates (μPLs), for the sustained release of therapeutic agents. μPLs are square hydrogel particles, with an edge length of 20 μm and a height of 5 μm, made out of poly(lactic- co-glycolic acid) (PLGA). During the synthesis process, the μPL Young's modulus can be varied from 0.6 to 5 MPa by changing the PLGA amounts from 1 to 7.5 mg, without affecting the μPL geometry while matching the properties of the surrounding tissue. Within the porous μPL matrix, different classes of therapeutic payloads can be incorporated including molecular agents, such as anti-inflammatory dexamethasone (DEX), and nanoparticles containing imaging and therapeutic molecules themselves, thus originating a truly hierarchical platform. As a proof of principle, μPLs are loaded with free DEX and 200 nm spherical polymeric nanoparticles, carrying DEX molecules (DEX-SPNs). Electron and fluorescent confocal microscopy analyses document the uniform distribution and stability of molecular and nanoagents within the μPL matrix. This multiscale, hierarchical microparticle releases DEX for at least 10 days. The inclusion of DEX-SPNs serves to minimize the initial burst release and modulate the diffusion of DEX molecules out of the μPL matrix. The biopharmacological and therapeutic properties together with the fine tuning of geometry and mechanical stiffness make μPLs a unique polymeric depot for the potential treatment of cancer, cardiovascular, and chronic, inflammatory diseases.

Dentin on the nanoscale: Hierarchical organization, mechanical behavior and bioinspired engineering

OBJECTIVE

Knowledge of the structural organization and mechanical properties of dentin has expanded considerably during the past two decades, especially on a nanometer scale. In this paper, we review the recent literature on the nanostructural and nanomechanical properties of dentin, with special emphasis in its hierarchical organization.

METHODS

We give particular attention to the recent literature concerning the structural and mechanical influence of collagen intrafibrillar and extrafibrillar mineral in healthy and remineralized tissues. The multilevel hierarchical structure of collagen, and the participation of non-collagenous proteins and proteoglycans in healthy and diseased dentin are also discussed. Furthermore, we provide a forward-looking perspective of emerging topics in biomaterials sciences, such as bioinspired materials design and fabrication, 3D bioprinting and microfabrication, and briefly discuss recent developments on the emerging field of organs-on-a-chip.

RESULTS

The existing literature suggests that both the inorganic and organic nanostructural components of the dentin matrix play a critical role in various mechanisms that influence tissue properties.

SIGNIFICANCE

An in-depth understanding of such nanostructural and nanomechanical mechanisms can have a direct impact in our ability to evaluate and predict the efficacy of dental materials. This knowledge will pave the way for the development of improved dental materials and treatment strategies.

CONCLUSIONS

Development of future dental materials should take into consideration the intricate hierarchical organization of dentin, and pay particular attention to their complex interaction with the dentin matrix on a nanometer scale.

Application of Hydrogel Template Strategy in Ocular Drug Delivery

The hydrogel template strategy was previously developed to fabricate homogeneous polymeric microparticles. Here, we demonstrate the versatility of the hydrogel template strategy for the development of nanowafer-based ocular drug delivery systems. We describe the fabrication of dexamethasone-loaded nanowafers using polyvinyl alcohol and the instillation of a nanowafer on a mouse eye. The nanowafer, a small circular disk, is placed on the ocular surface, and it releases a drug as it slowly dissolves over time, thus increasing ocular bioavailability and enhancing efficiency to treat eye injuries.

PLA micro- and nano-particles

Poly(d,l-lactic acid) (PLA) has been widely used for various biomedical applications for its biodegradable, biocompatible, and nontoxic properties. Various methods, such as emulsion, salting out, and precipitation, have been used to make better PLA micro- and nano-particle formulations. They are widely used as controlled drug delivery systems of therapeutic molecules, including proteins, genes, vaccines, and anticancer drugs. Even though PLA-based particles have challenges to overcome, such as low drug loading capacity, low encapsulation efficiency, and terminal sterilization, continuous innovations in particulate formulations will lead to development of clinically useful formulations.

Fabrication of Bacteria Environment Cubes with Dry Lift-Off Fabrication Process for Enhanced Nitrification

We have developed a 3D dry lift-off process to localize multiple types of nitrifying bacteria in polyethylene glycol diacrylate (PEGDA) cubes for enhanced nitrification, a two-step biological process that converts ammonium to nitrite and then to nitrate. Ammonia-oxidizing bacteria (AOB) is responsible for converting ammonia into nitrite, and nitrite-oxidizing bacteria (NOB) is responsible for converting nitrite to nitrate. Successful nitrification is often challenging to accomplish, in part because AOB and NOB are slow growers and highly susceptible to many organic and inorganic chemicals in wastewater. Most importantly, the transportation of chemicals among scattered bacteria is extremely inefficient and can be problematic. For example, nitrite, produced from ammonia oxidation, is toxic to AOB and can lead to the failure of nitrification. To address these challenges, we closely localize AOB and NOB in PEGDA cubes as microenvironment modules to promote synergetic interactions. The AOB is first localized in the vicinity of the surface of the PEGDA cubes that enable AOB to efficiently uptake ammonia from a liquid medium and convert it into nitrite. The produced nitrite is then efficiently transported to the NOB localized at the center of the PEGDA particle and converted into non-toxic nitrate. Additionally, the nanoscale PEGDA fibrous structures offer a protective environment for these strains, defending them from sudden toxic chemical shocks and immobilize in cubes. This engineered microenvironment cube significantly enhances nitrification and improves the overall ammonia removal rate per single AOB cell. This approach—encapsulation of multiple strains at close range in cube in order to control their interactions—not only offers a new strategy for enhancing nitrification, but also can be adapted to improve the production of fermentation products and biofuel, because microbial processes require synergetic reactions among multiple species.

On the development of multifunctional luminescent supramolecular hydrogel of gold and egg white

Highly stable, luminescent, and printable/paintable supramolecular egg white hydrogel-based surface enhanced Raman scattering (SERS) matrix is created by an in situ synthesis of gold clusters inside a luminescent egg white hydrogel (Au-Gel). The synthesis of stable luminescent egg-white-based hydrogel, where the hydrogel can act as a three dimensional (3D) matrix, using a simple cross-linking chemistry, has promising application in the biomedical field including in 3D cell culturing. Furthermore, this functional hydrogel is demonstrated for micromolar-level detection of Rhodamine 6G using the SERS technique, where Au-Gel is painted over a flexible cellulose pad.

Synergistic Cysteamine Delivery Nanowafer as an Efficacious Treatment Modality for Corneal Cystinosis

A synergy between the polymer biomaterial and drug plays an important role in enhancing the therapeutic efficacy, improving the drug stability, and minimizing the local immune responses in the development of drug delivery systems. Particularly, in the case of ocular drug delivery, the need for the development of synergistic drug delivery system becomes more pronounced because of the wet ocular mucosal surface and highly innervated cornea, which elicit a strong inflammatory response to the instilled drug formulations. This article presents the development of a synergistic cysteamine delivery nanowafer to treat corneal cystinosis. Corneal cystinosis is a rare metabolic disease that causes the accumulation of cystine crystals in the cornea resulting in corneal opacity and loss of vision. It is treated with topical cysteamine (Cys) eye drops that need to be instilled 6-12 times a day throughout the patient's life, which causes side effects such as eye pain, redness, and ocular inflammation. As a result, compliance and treatment outcomes are severely compromised. To surmount these issues, we have developed a clinically translatable Cys nanowafer (Cys-NW) that can be simply applied on the eye with a fingertip. During the course of the drug release, Cys-NW slowly dissolves and fades away. The in vivo studies in cystinosin knockout mice demonstrated twice the therapeutic efficacy of Cys-NW containing 10 μg of Cys administered once a day, compared to 44 μg of Cys as topical eye drops administered twice a day. Furthermore, Cys-NW stabilizes Cys for up to four months at room temperature compared to topical Cys eye drops that need to be frozen or refrigerated and still remain active for only 1 week. The Cys-NW, because of its enhanced therapeutic efficacy, safety profile, and extended drug stability at room temperature, can be rapidly translated to the clinic for human trials.

Controlled Release of Nor-β-lapachone by PLGA Microparticles: A Strategy for Improving Cytotoxicity against Prostate Cancer Cells

Prostate cancer is one of the most common malignant tumors in males and it has become a major worldwide public health problem. This study characterizes the encapsulation of Nor-β-lapachone (NβL) in poly(d,l-lactide-co-glycolide) (PLGA) microcapsules and evaluates the cytotoxicity of the resulting drug-loaded system against metastatic prostate cancer cells. The microcapsules presented appropriate morphological features and the presence of drug molecules in the microcapsules was confirmed by different methods. Spherical microcapsules with a size range of 1.03 ± 0.46 μm were produced with an encapsulation efficiency of approximately 19%. Classical molecular dynamics calculations provided an estimate of the typical adsorption energies of NβL on PLGA. Finally, the cytotoxic activity of NβL against PC3M human prostate cancer cells was demonstrated to be significantly enhanced when delivered by PLGA microcapsules in comparison with the free drug.

Bioerodable PLGA-Based Microparticles for Producing Sustained-Release Drug Formulations and Strategies for Improving Drug Loading

Poly(lactic-co-glycolic acid) (PLGA) is the most widely used biomaterial for microencapsulation and prolonged delivery of therapeutic drugs, proteins and antigens. PLGA has excellent biodegradability and biocompatibility and is generally recognized as safe by international regulatory agencies including the United States Food and Drug Administration and the European Medicines Agency. The physicochemical properties of PLGA may be varied systematically by changing the ratio of lactic acid to glycolic acid. This in turn alters the release rate of microencapsulated therapeutic molecules from PLGA microparticle formulations. The obstacles hindering more widespread use of PLGA for producing sustained-release formulations for clinical use include low drug loading, particularly of hydrophilic small molecules, high initial burst release and/or poor formulation stability. In this review, we address strategies aimed at overcoming these challenges. These include use of low-temperature double-emulsion methods to increase drug-loading by producing PLGA particles with a small volume for the inner water phase and a suitable pH of the external phase. Newer strategies for producing PLGA particles with high drug loading and the desired sustained-release profiles include fabrication of multi-layered microparticles, nanoparticles-in-microparticles, use of hydrogel templates, as well as coaxial electrospray, microfluidics, and supercritical carbon dioxide methods. Another recent strategy with promise for producing particles with well-controlled and reproducible sustained-release profiles involves complexation of PLGA with additives such as polyethylene glycol, poly(ortho esters), chitosan, alginate, caffeic acid, hyaluronic acid, and silicon dioxide.

Effects of the Microparticle Shape on Cellular Uptake

Physical forms of microparticles and nanoparticles, such as the size, charge, and shape, are known to affect endocytosis. Improving the physical designs of the drug carriers can increase the drug uptake efficiency and the subsequent drug efficacy. Simple shapes, such as sphere and cylinder, have been studied for their ability for endocytosis. To have a better understanding of the shape effect on cellular uptake, different particle shapes were prepared, using the keyboard character shapes, and their impacts on cellular uptake were examined. The results showed that shapes with higher aspect ratios and sharper angular features have a higher chance of adhering to the cells and become internalized by the cancer cells. The local interaction between the cell membrane and the part of the microparticle in contact with the cell membrane also plays a crucial role in determining the outcome.

Soft Discoidal Polymeric Nanoconstructs Resist Macrophage Uptake and Enhance Vascular Targeting in Tumors

Most nanoparticles for biomedical applications originate from the self-assembling of individual constituents through molecular interactions and possess limited geometry control and stability. Here, 1000 × 400 nm discoidal polymeric nanoconstructs (DPNs) are demonstrated by mixing hydrophobic and hydrophilic polymers with lipid chains and curing the resulting paste directly within silicon templates. By changing the paste composition, soft- and rigid-DPNs (s- and r-DPNs) are synthesized exhibiting the same geometry, a moderately negative surface electrostatic charge (-14 mV), and different mechanical stiffness (∼1.3 and 15 kPa, respectively). Upon injection in mice bearing nonorthotopic brain or skin cancers, s-DPNs exhibit ∼24 h circulation half-life and accumulate up to ∼20% of the injected dose per gram tumor, detecting malignant masses as small as ∼0.1% the animal weight via PET imaging. This unprecedented behavior is ascribed to the unique combination of geometry, surface properties, and mechanical stiffness which minimizes s-DPN sequestration by the mononuclear phagocyte system. Our results could boost the interest in using less conventional delivery systems for cancer theranosis.