Severe blood loss due to traumatic injuries remains one of the leading causes of death in emergency settings. Chitosan continues to be the candidate material for hemostatic applications due to its inherent hemostatic properties. However, available chitosan-based dressings have been reported to have an acidic odor at the wound site due to the incorporation of acid based solvents for their fabrication and deformation under compression owing to low mechanical strength limiting its usability. In the present study semi-IPN cryogel was fabricated via Schiff's base cross-linking between the polyaldehyde groups of oxidized dextran and thiolated chitosan in presence of locust bean gum (LBG) known for its hydrophilicity. Polymerization at −12 °C yielded macroporous semi-IPN cryogels with an average pore size of 124.57 ± 20.31 μm and 85.46% porosity. The hydrophobicity index of LBG reinforced semi-IPN cryogel was reduced 2.42 times whereas the swelling ratio was increased by 156.08% compare to control cryogel. The increased hydrophilicity and swelling ratio inflated the compressive modulus from 28.1 kPa to 33.85 for LBG reinforced semi-IPN cryogel. The structural stability and constant degradation medium pH were also recorded over a period of 12 weeks. The cryogels demonstrated lower adsorption affinity towards BSA. The cytotoxicity assays (direct, indirect) with 3T3-L1 fibroblast cells confirmed the cytocompatibility of the cryogels. The hemolysis assay showed <5% hemolysis confirming blood compatibility of the fabricated cryogel, while whole blood clotting and platelet adhesion assays confirmed the hemostatic potential of semi-IPN cryogel.

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Dual delivery of bioactive molecules (drugs and growth factors) has been attempted to enhance multiple processes during tissue regeneration. For bone tissue engineering, many attempts have been made to enhance osteogenesis coupled angiogenesis, which plays a major role during the bone regeneration process. In this study, core−shell microgels were fabricated for controlled release of recombinant human bone morphogenetic protein 2 (rhBMP-2) and simvastatin from the core and shell, respectively. The microgels were formed with a discrete core and shell structure. The Fourier transform infrared analysis demonstrated the composition of microgel, whereas swelling behavior demonstrated its rapid swelling property. Thermal properties demonstrated the ionic gelation in microgels, which minimizes the thermal degradation of polymers. The degradation study demonstrates that the core−shell structure of microgels was intact until 49 days under physiological conditions. The release profile demonstrates the sequential and controlled release of rhBMP-2 from the core and simvastatin from the shell of the microgels, respectively. The bioactivity of rhBMP-2 and simvastatin released from microgels was preserved as indicated by the alkaline phosphatase (ALP) activity assay. The cell proliferation of mouse preosteoblast (MC3T3-E1) cells and the live−dead staining assay demonstrated cytocompatibility of the microgels. Scanning electron microscopy images demonstrate that the microgels support adhesion of cells on the surface and promote extracellular matrix (ECM) production. The osteogenic differentiation of MC3T3-E1 cells demonstrated the synergistic effect of drugs and growth factors up to 21 days. The controlled and sustained release of simvastatin and rhBMP-2 induced higher mRNA and protein expressions of RUNX2, osteocalcin, and VEGF. The overall results demonstrate the effect of controlled release of rhBMP-2 and simvastatin from core−shell microgels to promote osteogenesis and angiogenesis.