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.

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

Despite advances in the development of degradable polymers for drug delivery, effective translation of drug-loaded materials is often hindered due to a poor understanding of matrix property combinations that promote controlled and sustained release. In this study, we investigated the influence of dominant factors on the release of a hydrophobic glucocorticoid dexamethasone (DEX) from electrospun meshes. Polycaprolactone meshes released 98% of the drug within 24 h, while poly(l-lactide) meshes exhibited negligible release even after 28 days despite both polymers being slow-degrading. Differences in drug-polymer interactions and drug-polymer miscibility-but neither matrix degradation nor differences in bulk hydrophobicity-influenced DEX release from these semi-crystalline matrices. Poly(d,l-lactide-co-glycolide) 50:50 meshes possessing two different fiber diameters exhibited a sequential burst and sustained release, while poly(d,l-lactide-co-glycolide) 85:15 meshes cumulatively released 26% drug in a controlled manner. Although initial drug release from these matrices was driven by differences in matrix architecture and solid-state drug solubility, release toward the later stages was influenced by a combination of fiber swelling and matrix degradation as evidenced by gross and microstructural changes to the mesh network. We suggest that drug release from polymeric matrices can be better understood via investigation of critical matrix characteristics influencing release, as well as concomitant examination of drug-polymer interactions and miscibility. Our findings offer rational matrix design criteria to achieve controlled/extended drug release for promoting sustained biological responses.

Immunoregulation of macrophages by dynamic ligand presentation via ligand-cation coordination

Macrophages regulate host responses to implants through their dynamic adhesion, release, and activation. Herein, we employ bisphosphonate (BP)-coated gold nanoparticle template (BNP) to direct the swift and convertible formation of Mg²⁺-functional Mg²⁺-BP nanoparticle (NP) on the BP-AuNP surface via reversible Mg²⁺-BP coordination, thus producing (Mg²⁺-BP)-Au dimer (MgBNP). Ethylenediaminetetraacetic acid-based Mg²⁺ chelation facilitates the dissolution of Mg²⁺-BP NP, thus enabling the reversion of the MgBNP to the BNP. This convertible nanoassembly incorporating cell-adhesive Mg²⁺ moieties directs reversible attachment and detachment of macrophages by BP and EDTA, without physical scraping or trypsin that could damage cells. The swift formation of RGD ligand- and Mg²⁺-bifunctional RGD-Mg²⁺-BP NP that yields (RGD-Mg²⁺-BP)-Au dimer (RGDBNP) further stimulates the adhesion and pro-regenerative M2-type polarization of macrophages, both in vitro and in vivo, including rho-associated protein kinase. This swift and non-toxic dimer formation can include diverse bio-functional moieties to regulate host responses to implants.

Control of macrophage adhesion and phenotype is important to biomaterial applications. Here, the authors report on the use of bisphosphonate coated gold nanoparticles by magnesium coordination for the controlled adhesion and polarisation of macrophages in vitro and in vivo and controlled cell release.

Facile and Versatile Strategy for Construction of Anti-Inflammatory and Antibacterial Surfaces with Polydopamine-Mediated Liposomes Releasing Dexamethasone and Minocycline for Potential Implant Applications

Reducing early nonbacterial inflammation induced by implanted materials and infection resulting from bacterial contamination around the implant-abutment interface could greatly decrease implant failure rates, which would be of clinical significance. In this work, we presented a facile and versatile strategy for the construction of anti-inflammatory and antibacterial surfaces. Briefly, the surfaces of polystyrene culture plates were first coated with polydopamine and then decorated with dexamethasone plus minocycline-loaded liposomes (Dex/Mino liposomes), which was validated by contact angle goniometry, quartz crystal microbalance, and fluorescence microscopy. Dex/Mino liposomes were dispersed on functional surfaces and the drug release kinetics exhibited the sustained release of dexamethasone and minocycline. Our results demonstrated that the Dex/Mino liposome-modified surfaces had good biocompatibility. Additionally, liposomal dexamethasone reduced proinflammatory mediator expression (particularly IL-6 and TNF-α) in lipopolysaccharide-stimulated human gingival fibroblasts and human mesenchymal stem cells. Moreover, liposomal minocycline prevented the adhesion and proliferation of Porphyromonas gingivalis (Gram-negative bacteria) and Streptococcus mutans (Gram-positive bacteria). These findings demonstrate that an anti-inflammatory and antibacterial surface was developed, using dopamine as a medium and combining a liposomal delivery device, which has potential for use to reduce implant failure rates. Accordingly, the surface modification strategy presented could be useful in biofunctionalization of implant materials.

A Novel Electroactive Agarose-Aniline Pentamer Platform as a Potential Candidate for Neural Tissue Engineering

Neuronal disorder is an important health challenge due to inadequate natural regeneration, which has been responded by tissue engineering, particularly with conductive materials. A bifunctional electroactive scaffold having agarose biodegradable and aniline pentamer (AP) conductive parts was designed that exhibits appropriate cell attachment/compatibility, as detected by PC12 cell seeding. The developed carboxyl-capped aniline-pentamer improved agarose cell adhesion potential, also the conductivity of scaffold was in the order 10-5 S/cm reported for cell membrane. Electrochemical impedance spectroscopy was applied to plot the Nyquist graph and subsequent construction of the equivalent circuit model based on the neural model, exhibiting an appropriate cell signaling and an acceptable consistency between the components of the scaffold model with neural cell model. The ionic conductivity was also measured; exhibiting an enhanced ionic conductivity, but lower activation energy upon a temperature rise. Swelling behavior of the sample was measured and compared with pristine agarose; so that aniline oligomer due to its hydrophobic nature decreased water uptake. Dexamethasone release from the developed electroactive scaffold was assessed through voltage-responsive method. Proper voltage-dependent drug release could be rationally expected because of controllable action and elimination of chemically responsive materials. Altogether, these characteristics recommended the agarose/AP biopolymer for neural tissue engineering.

Modulating Immunological Responses of Electrospun Fibers for Tissue Engineering

The promise of tissue engineering is to improve or restore functions of impaired tissues or organs. However, one of the biggest challenges to its translation to clinical applications is the lack of tissue integration and functionality. The plethora of cellular and molecular events occurring following scaffold implantation is a major bottleneck. Recent studies confirmed that inflammation is a crucial component influencing tissue regeneration. Immuno-modulation or immune-engineering has been proposed as a potential solution to overcome this key challenge in regenerative medicine. In this review, strategies to modify scaffold physicochemical properties through the use of the electrospinning technique to modulate host response and improve scaffold integration will be discussed. Electrospinning, being highly versatile allows the fabrication of ECM-mimicking scaffolds and also offers the possibility to control scaffold properties for instance, tailoring of fiber properties, chemical conjugation or physical adsorption of non-immunogenic materials on the scaffold surface, encapsulating cells or anti-inflammatory molecules within the scaffold. Such electrospun scaffold-based immune-engineering strategies can significantly improve the resulting outcomes of tissue engineering scaffolds.

ECM–oligourethene–silica hydrogels as a local drug release system of dexamethasone for stimulating macrophages

The incorporation of silica particles inside of extracellular matrix hydrogels supports the loading and releasing of dexamethasone, a therapeutic for modulating macrophage.