Identifying Specific Combinations of Matrix Properties that Promote Controlled and Sustained Release of a Hydrophobic Drug from Electrospun Meshes

Evaluating the protective effects of dexamethasone and electrospun mesh combination on primary human mixed retinal cells under hyperglycemic stress

Chronic inflammation is a leading cause of neurodegeneration and vision loss in hyperglycemia-associated conditions such as diabetic retinopathy. Corticosteroid injections are widely used for treatment but suffer from limitations such as rapid drug clearance, short drug half-lives and frequent administration. While drug release from biomaterial carriers can overcome these shortcomings, evaluating the combined effects of corticosteroids and polymeric matrices under hyperglycemic stress is an important step towards aiding translation. In this study, we investigated the effects of dexamethasone (DEX) and electrospun mesh combination on primary human mixed retinal cells under normal and hyperglycemic culture conditions. DEX-incorporated poly(lactide-co-glycolide) (PLGA) meshes were prepared and characterized for architecture, chemistry, drug distribution and in vitro release. The meshes exhibited cumulative in vitro drug release of 39.5 % over 2 months at a near constant rate. Under normal culture conditions, DEX-PLGA meshes promoted significantly higher viability of mixed retinal cells than the control groups but without adverse phenotypic activation. Under hyperglycemic conditions, DEX supplementation resulted in higher viability than the control, although the highest viability was achieved only when DEX was added to cells cultured on PLGA fibers. The combination of DEX and PLGA fibers also promoted higher mRNA expression of the antioxidant GSH under hyperglycemia. Importantly, the largest reduction in the production of pro-inflammatory cytokines viz., MMP-9, IL-6, IL-8 and VEGF-R1 was observed for the DEX and PLGA combination. Our study reveals a combined effect of DEX and electrospun fibers in combating hyperglycemia-driven pro-inflammatory responses, which can aid the development of DEX-loaded electrospun implants for diabetes-driven retinal conditions.

Evaluation of Electrospun PCL-PLGA for Sustained Delivery of Kartogenin

In this study, kartogenin was incorporated into an electrospun blend of polycaprolactone and poly(lactic-co-glycolic acid) (1:1) to determine the feasibility of this system for sustained drug delivery. Kartogenin is a small-molecule drug that could enhance the outcome of microfracture, a cartilage restoration procedure, by selectively stimulating chondrogenic differentiation of endogenous bone marrow mesenchymal stem cells. Experimental results showed that kartogenin did not affect the electrospinnability of the polymer blend, and it had negligible effects on fiber morphology and scaffold mechanical properties. The loading efficiency of kartogenin into electrospun membranes was nearly 100%, and no evidence of chemical reaction between kartogenin and the polymers was detected by Fourier transform infrared spectroscopy. Analysis of the released drug using high-performance liquid chromatography-photodiode array detection indicated an abundance of kartogenin and only a small amount of its major hydrolysis product. Kartogenin displayed a typical biphasic release profile, with approximately 30% being released within 24 h followed by a much slower, constant rate of release up to 28 days. Although additional development is needed to tune the release kinetics and address issues common to electrospun scaffolds (e.g., high fiber density), the results of this study demonstrated that a scaffold electrospun from biodegradable synthetic polymers is a suitable kartogenin delivery vehicle.

Electrospun fiber-based strategies for controlling early innate immune cell responses: Towards immunomodulatory mesh designs that facilitate robust tissue repair

Electrospun fibrous meshes are widely used for tissue repair due to their ability to guide a host of cell responses including phenotypic differentiation and tissue maturation. A critical factor determining the eventual biological outcomes of mesh-based regeneration strategies is the early innate immune response following implantation. The natural healing process involves a sequence of tightly regulated, temporally varying and delicately balanced pro-/anti-inflammatory events which together promote mesh integration with host tissue. Matrix designs that do not account for the immune milieu can result in dysregulation, chronic inflammation and fibrous capsule formation, thus obliterating potential therapeutic outcomes. In this review, we provide systematic insights into the effects of specific fiber/mesh properties and mechanical stimulation on the responses of early innate immune modulators viz., neutrophils, monocytes and macrophages. We identify matrix characteristics that promote anti-inflammatory immune phenotypes, and we correlate such responses with pro-regenerative in vivo outcomes. We also discuss recent advances in 3D fabrication technologies, bioactive functionalization approaches and biomimetic/bioinspired immunomodulatory mesh design strategies for tissue repair and wound healing. The mechanobiological insights and immunoregulatory strategies discussed herein can help improve the translational outcomes of fiber-based regeneration and may also be leveraged for intervention in degenerative diseases associated with dysfunctional immune responses. STATEMENT OF SIGNIFICANCE: The crucial role played by immune cells in promoting biomaterial-based tissue regeneration is being increasingly recognized. In this review focusing on the interactions of innate immune cells (primarily neutrophils, monocytes and macrophages) with electrospun fibrous meshes, we systematically elucidate the effects of the fiber microenvironment and mechanical stimulation on biological responses, and build upon these insights to inform the rational design of immunomodulatory meshes for effective tissue repair. We discuss state-of-the-art fabrication methods and mechanobiological advances that permit the orchestration of temporally controlled phenotypic switches in immune cells during different phases of healing. The design strategies discussed herein can also be leveraged to target several complex autoimmune and inflammatory diseases.

Drug release study of the chitosan-based nanoparticles

Recently, multifunctional drug delivery systems (DDSs) have been designed to provide a comprehensive approach with multiple functionalities, including diagnostic imaging, targeted drug delivery, and controlled drug release. Chitosan-based drug nanoparticles (CSNPs) systems are employed as diagnostic imaging and delivering the drug to particular targeted sites in a regulated manner. Drug release is an important factor in ensuring high reproducibility, stability, quality control of CSNPs, and scientific-based for developing CSNPs. Several factors influence drug release from CSNPs, including composition, composition ratio, ingredient interactions, and preparation methods. Early, CSNPs were used for improving drug solubility, stability, pharmacokinetics, and pharmacotherapeutics properties. Chitosan has been developed toward a multifunctional drug delivery system by exploring positively charged properties and modifiable functional groups. Various modifications to the polymer backbone, charge, or functional groups will undoubtedly affect the drug release from CSNPs. The drug release from CSNPs has a significant influence on its therapeutic actions. Our review's objective was to summarize and discuss the relationship between the modification in CSNPs as multifunctional delivery systems and drug release properties and kinetics of the drug release model. Kinetic models help describe the release rate, leading to increased efficiency, accuracy, the safety of the dose, optimizing the drug delivery device's design, evaluating the drug release rate, and improvement of patient compatibility. In conclusion, almost all CSNPs showed bi-phasic release, initial burst release drug in a particular time followed controlled manner release in achieving the expected release, stimuli external can be applied. CSNPs are a promising technique for multifunctional drug delivery systems.

Potent Particle-Based Vehicles for Growth Factor Delivery from Electrospun Meshes: Fabrication and Functionalization Strategies for Effective Tissue Regeneration

Functionalization of electrospun meshes with growth factors (GFs) is a common strategy for guiding specific cell responses in tissue engineering. GFs can exert their intended biological effects only when they retain their bioactivity and can be subsequently delivered in a temporally controlled manner. However, adverse processing conditions encountered in electrospinning can potentially disrupt GFs and diminish their biological efficacy. Further, meshes prepared using conventional approaches often promote an initial burst and rely solely on intrinsic fiber properties to provide extended release. Sequential delivery of multiple GFs─a strategy that mimics the natural tissue repair cascade─is also not easily achievable with traditional fabrication techniques. These limitations have hindered the effective use and translation of mesh-based strategies for tissue repair. An attractive alternative is the use of carrier vehicles (e.g., nanoparticles, microspheres) for GF incorporation into meshes. This review presents advances in the development of particle-integrated electrospun composites for safe and effective delivery of GFs. Compared to traditional approaches, we reveal how particles can protect GF activity, permit the incorporation of multiple GFs, decouple release from fiber properties, help achieve spatiotemporal control over delivery, enhance surface bioactivity, exert independent biological effects, and augment matrix mechanics. In presenting innovations in GF functionalization and composite engineering strategies, we also discuss specific in vitro and in vivo biological effects and their implications for diverse tissue engineering applications.