Janani Radhakrishnan

Macrophage phenotypic switching from pro-inflammatory M1 to pro-regenerative M2 is impaired in chronic diabetic wounds, leading to excessive reactive oxygen species (ROS) production, poor angiogenesis, and decreased collagen deposition, thereby affecting the healing cascade. Development of multifunctional biomaterial with bioactive compounds to modulate the immune microenvironment and combat ROS, with the potential to facilitate angiogenesis and increase collagen deposition. Here, a novel combination therapy of silk DOPA–crisaborole conjugate (SDC, angiogenic and anti-inflammatory) and eugenol (Eu, antioxidant) has been devised to promote chronic wound healing. The core–shell electrospun fibrous mat has been fabricated with Eu in a polycaprolactone core (PCL-Eu) and SDC in a dextran shell (Dex-SDC), collectively termed Dex-SDC/PCL-Eu. In response to the acidic environment of chronic wounds, the dynamic benzoxaborole–catechol complex between crisaborole and silk DOPA cleaves, releasing crisaborole, while the matrix degradation of Dex-SDC/PCL-Eu over time enables the controlled release of Eu for 12 days. The initial release of crisaborole promotes polarization of M1 macrophages to M2 phenotype by significantly upregulating anti-inflammatory cytokine IL-10 and downregulating pro-inflammatory cytokine IL-6 gene expression in Dex-SDC/PCL-Eu-treated THP-1 cells compared to control. Subsequently, the sustained release of Eu mitigates oxidative damage. Dex-SDC/PCL-Eu fibers facilitate in vitro adhesion, migration, and proliferation of fibroblasts and endothelial cells as well as enhance endothelial tube formation. In the diabetic rat model, the Dex-SDC/PCL-Eu fibers reduce inflammatory granulation tissue and ulceration, while promoting neovascularization, complete re-epithelialization, and well-organized dermis and epidermis formation with uniform collagen deposition. Thus, the developed multifunctional Dex-SDC/PCL-Eu fibrous mat accelerates full-thickness skin wound healing and holds promise for the treatment of chronic diabetic wounds.

Biofabrication of cardiac tissue constructs with inherent electrical conductivity and contractility presents a significant challenge. In this study, an interpenetrating network (IPN) hydrogel composed of polysaccharide gellan gum (GG) and methacrylate-modified polyvinyl alcohol (M-PVA) reinforced with reduced graphene oxide (rGO) has been developed. The M-PVA/GG/rGO hydrogel leverages thermoresponsive property of GG for controlled gelation during 3D printing process, followed by photocrosslinking of M-PVA to enhance structural stability post-printing. Weak gel formed by physical gelation of GG provides mechanical stability to the hydrogel that enables printing of defined structures. IPN hydrogel exhibited porous morphology with interconnected pores, high porosity, swellability, and significant electrical conductivity (0.62 ± 0.05 mS/cm) imparted by the inclusion of rGO. Rheological analysis demonstrated the shear-thinning property and predominant elastic modulus of the developed hydrogel, thereby suitable for pneumatic extrusion-based 3D printing. The printed constructs cultured with H9c2 cardiomyoblasts and EA. hy926 endothelial cells demonstrated favorable in vitro cell viability, proliferation, and cardiac specific gene expression, influenced by the matrix composition. The dual-crosslinked, electroconductive M-PVA/GG/rGO hydrogel shows significant promise for promoting vascularization in cardiac tissue engineering, facilitating tissue regeneration, develop organotypic models, and potentially enabling the development of electroconductive biomedical devices. Key words: Gellan gum, Methacrylate Polyvinyl Alcohol, Photocrosslinking, Thermoresponsive, 3D printing, Cardiac regeneration

Collagen occurs in nature with a dedicated triple helix structure and is the most preferred biomaterial in commercialized medical products. Recombinant collagen emerge as sustainable alternate source that overcomes existing demerits.

The healing physiology of bone repair and remodeling that occurs after normal fracture is well orchestrated. However, it fails in complex clinical conditions and hence requires augmentation by grafts. In this study, composite nanohydroxyapatite (nHA), poly(hydroxybutyrate) (PHB) and poly(ɛ-caprolactone) (PCL) constituted microspheres sintered three-dimensional scaffold were evaluated in rabbit ulnar segmental defect. A composite scaffold using PHB-PCL-nHA microspheres was developed with protein interface by solvent/non-solvent sintering to provide multiple cues such as biocomposition, cancellous bone equivalent meso-micro multi-scale porosity, and compressive strength. In vitro DNA quantification and alkaline phosphatase (ALP) assays revealed that the protein interfaced composite scaffolds supported osteoblast proliferation and mineralization significantly higher than scaffolds without protein and TCPS (p < 0.05). Scanning electron micrographs of osteoblasts cultured scaffolds demonstrated cell-matrix interaction, cell spreading, colonization and filopodial extension across the porous voids. Cylindrical scaffolds (5 × 10 mm) were implanted following segmental defect (10 mm) in rabbit ulnar bone and compared with untreated control. Radiography (4, 8 and 12 weeks) and µ-computed tomography (12 weeks) analysis showed directional bone tissue formation by bridging defective site in both scaffolds with and without protein interface. Whereas, undesired sclerotic-like tissue formation was observed in control groups from 8 weeks. Histology by hot Stevenel’s blue and van Gieson’s picrofuchsin staining has confirmed enhanced bone maturation in scaffold groups while presence of osteoids was observed in control after 12 weeks. Thus, the developed composite matrices exhibits osteoinductive, osteoconductive properties and demonstrates its bone regenerative potential owing to its compositional, micro & macro structural and mechanical properties.

Reconstruction of peripheral nervous tissue remains challenging in critical-sized defects due to the lack of Büngner bands from the proximal to the distal nerve ends. Conventional nerve guides fail to bridge the large-sized defect owing to the formation of a thin fibrin cable. Hence, in the present study, an attempt was made to reverse engineer the intricate epi-, peri- and endo- neurial tissues using Fused Deposition Modeling (FDM) based 3D printing. Bovine serum albumin protein nanoflowers (BSA-NF) exhibiting Viburnum opulus 'Roseum’ morphology were ingrained into 3D printed constructs without affecting its secondary structure to enhance the axonal guidance from proximal to distal ends of denuded nerve ends. Scanning electron micrographs confirmed the uniform distribution of protein nanoflowers in 3D printed constructs. The PC-12 cells cultured on protein ingrained 3D printed scaffolds demonstrated cytocompatibility, improved cell adhesion and extended neuronal projections with significantly higher intensities of NF-200 and tubulin expressions. Further suture-free fixation designed in the current 3D printed construct aids facile implantation of printed conduits to the transected nerve ends. Hence the protein ingrained 3D printed construct would be a promising substitute to treat longer peripheral nerve defects as its structural equivalence of endo- and perineurial organization along with the ingrained protein nanoflowers promote the neuronal extension towards the distal ends by minimizing axonal dispersion.