Arun Kumar Teotia

Treatment of large-size bone defects is difficult, and acquiring autografts may be challenging due to limited availability. A synthetic patient-specific bone substitute can be developed by using 3D printing technologies in such cases. In the present study, we have developed photocurable composite resins with poly(trimethylene carbonate) (PTMC) containing a high percentage of biodegradable bioactive strontium-substituted nanohydroxyapatite (SrHA, size 30-70 nm). These photocurable resins have then been employed to develop high-surface-area 3D-printed bone substitutes using the digital light processing (DLP) technique. To enhance the surface area of the 3D-printed substitute, cryogels alone and functionalized with bioactive components of bone morphogenetic protein (BMP) and zoledronic acid (ZA) were filled within the 3D-printed scaffold/substitute. The scaffolds were tested in vitro for biocompatibility and functionality in vivo in two therapeutically relevant rat models with large bone defects (4 mm). The porosities of 3D printed scaffolds were found to be 60.1 ± 0.9%, 72.9 ± 0.5%, and 74.3 ± 1.6% for PTMC, PTMC-HA, and PTMC-SrHA, respectively, which is in the range of cancellous bone (50-95%). The thermogravimetric analysis demonstrated the fabrication of 3D printed composites with HA and SrHA concentrations of 51.5 and 57.4 wt %, respectively, in the PTMC matrix. The tensile Young's modulus (E), compressive moduli, and wettability increased post incorporation of SrHA and HA in the PTMC matrix. In vitro and in vivo results revealed that SrHA integrated into the PTMC matrix exhibited good physicochemical and biological properties. Furthermore, the osteoactive molecule-functionalized 3D printed composite scaffolds were found to have an adequate osteoconductive and osteoinductive surface that has shown increased bone regeneration and defect repair in both tibial and cranial bone defects. Our findings thus support the use of PTMC-SrHA composites as next-generation patient-specific synthetic bioactive biodegradable bone substitutes.

Cationically modified chitosan derivatives exhibit a range of appealing characteristics, with a particular emphasis on their antimicrobial potential across a broad spectrum of biomedical applications. This study aimed to delve deeper into quaternary chitosan (QC) derivatives. Through the synthesis of both homogeneously and heterogeneously dual-quaternized chitosan (DQC), utilizing AETMAC ([2-(acryloyloxy)ethyl]-trimethylammonium chloride) and GTMAC (glycidyl trimethylammonium chloride), a permanent charge was established, spanning a wide pH range. We assessed structural differences, the type of quaternary functional group, molecular weight (M_w), and charge density. Intriguingly, an upper critical solution temperature (UCST) behavior was observed in AETMAC-functionalized QC. To our knowledge, it is a novel discovery in cationically functionalized chitosan. These materials demonstrated excellent antimicrobial efficacy against model test organisms E. coli and P. syringae. Furthermore, we detected concentration-dependent cytotoxicity in NIH-3T3 fibroblasts. Striking a balance between antimicrobial activity and cytotoxicity becomes a crucial factor in application feasibility. AETMAC-functionalized chitosan emerges as the top performer in terms of overall antibacterial effectiveness, possibly owing to factors like molecular weight, charge characteristics, and variations in the quaternary linker. Quaternary chitosan derivatives, with their excellent antibacterial attributes, hold significant promise as antibacterial or sanitizing agents, as well as across a broad spectrum of biomedical and environmental contexts.

Due to increasing public concern over hygiene, there have been many studies investigating antimicrobial and antiviral agents recently. With the aim of developing biobased virucidal/virus capture agents, we report a chemical modification of the cellulose nanocrystals (CNCs) surface with poly(2-dimethylamino) ethyl acrylate) methyl chloride quaternary salt (Q-PDMAEA) to introduce the positively charged functional groups. The surface of CNCs was modified through direct and indirect graft polymerization. Subsequently, the direct and indirect cationization effect on the degree of functionalization, thermal stability, crystallinity, and antiviral activity of CNCs was investigated. Indirect cationization produced the highest degree of polymer grafting, increasing particle size and thermal stability. Further, the modified CNCs were tested for their ability to capture nonenveloped bacteriophages PhiX174 (ΦX174) and MS2. We observed a significant (>4.19 log₁₀) reduction in total viral load by specific functionalized CNCs. However, the activity depended on the structure of functional groups, surface charge density, and the type of virus under study. Overall, the direct and indirect cationization of CNC leads to biobased agents with immobilized cationic charge, with good virus capture activity. Such agents can be used for various applications including textiles, packaging, wastewater treatment, etc.

Long term multiple systemic antibiotics form the cornerstone in the treatment of bone and joint tuberculosis, often combined with local surgical eradication. Implanted carriers for local drug delivery have recently been introduced to overcome some of the limitations associated with conventional treatment strategies. In this study, we used a calcium sulphate hemihydrate (CSH)/nanohydroxyapatite (nHAP) based nanocement (NC) biomaterial as a void filler as well as a local delivery carrier of two standard of care tuberculosis drugs, Rifampicin (RFP) and Isoniazid (INH). We observed that the antibiotics showed different release patterns where INH showed a burst release of 67% and 100% release alone and in combination within one week, respectively whereas RFP showed sustained release of 42% and 49% release alone and in combination over a period of 12 weeks, respectively indicating different possible interactions of antibiotics with nHAP. The interactions were studied using computational methodology, which showed that the binding energy of nHAP with RFP was 148 kcal/mol and INH was 11 kcal/mol, thus varying substantially resulting in RFP being retained in the nHAP matrix. Our findings suggest that a biphasic ceramic based drug delivery system could be a promising treatment alternative to bone and joint TB.

Withania somnifera (ashwagandha) is used in Indian traditional medicine for its various health benefits. Withaferin-A, a steroidal lactone present in this herb, has shown proteosomal inhibition-based enhancement of bone mineralization. In the present work, chitosan microparticles blended with total methanolic root extract of W. somnifera were incorporated as a porogen in calcium phosphate-based hydroxyapatite bone filler. The controlled release of bioactive molecules enabled enhanced proliferation and differentiation of pre-osteoblasts. Microparticle percentages were optimized to have a minimum effect on the setting time, mechanical strength and degradability of hydroxyapatite bone filler. In vitro cell adhesion, proliferation and differentiation were evaluated to determine the biocompatibility of the composites. On the basis of the desirable results obtained, we provide a preliminary rationale for the use of methanolic extract-blended chitosan microparticle-impregnated calcium phosphate filler for enhanced bone regeneration.

Hip fractures are among the most common types of fracture risks in old age osteoporotic patients that often end up with immobile disabilities. Weak bones due to loss of mineral content along with increase in the porosity of femur neck canal in osteoporosis reduces the mechanical properties of the bone and pre-disposes the patients to fractures. In this study we have used calcium sulphate/nanohydroxyapatite based nanocement (NC) as carrier of recombinant human bone morphogenetic protein-2 (BMP-2), zoledronate (ZA) and bone marrow mesenchymal stromal cells (MSCs) derived exosomes (EXO) to enhance bone formation and defect healing in femur neck canal defect model in osteoporotic rats. A cylindrical defect in femur neck canal with dimensions of 1 mm (diameter) ⅹ 8 mm (length) starting from later cortex towards the apex of femur head was developed. The defect was impacted using NC alone or functionalized as; a) NC+ZA (systemic), b) NC+ZA (local), c) NC+EXO+ZA and d) NC+BMP+ZA to evaluate bone formation by ex vivo micro-CT and histological analysis 16 weeks post-surgery. Moreover, the femurs (both defect and contralateral leg) were subjected to biomechanical analysis to assess the effect of treatments on compressive mechanical properties of bones. The treatment groups (NC+ZA (L), NC+BMP+ZA and NC+EXO+ZA) showed enhanced bone formation with complete healing of the defect. No differences in the mechanical properties of both the defect and contralateral across leg were observed among the groups. However, a trend was observed where NC+BMP+ZA showed enhanced biomechanical strength in defect leg. This suggests that NC could act as a potent carrier of bioactive molecules to reduce the risks of hip fractures in osteoporotic animals. This type of treatment can be given to patients who are at higher risk of osteoporosis mediated femur neck fracture as preventive measure or for enhanced healing in already compromised situation. Moreover, this study provided a proof of concept regarding use of exosomes in bone regeneration therapy which might be used as a booster dose that will eventually reduce the dosage of BMP and hence circumvent the limitations associated with use of BMP.

Human liver tissue is preferable over nonhuman liver tissue for preclinical drug screening, as the former can better predict side effects specific to humans. However, due to limited supply and ethical issues with human liver tissue, it is desirable to develop an animal model having functional human liver tissue. In this study, we have established an ectopic functional human liver tissue in a mouse model, using a minimally‐invasive method. Firstly, a human liver tissue mass using HepG2 cells and poly(N‐isopropylacrylamide) (PNIPAAm) incorporated poly(ethylene glycol)‐alginate‐gelatin (PAG) cryogel matrix was developed in vitro. It was later implanted in mouse peritoneal cavity using a 16 G needle. Viscoelastic nature along with low Young's modulus provided injectable properties to the cryogel. We confirmed minimal cell loss/death while injecting. Further, by in vivo study efficacy of both injectable and surgical implantation approaches were compared. No significant difference in terms of cell infiltration, human serum albumin (HSA) secretion and enzyme activity confirmed efficacy. This model developed using a minimally‐invasive approach can overcome the limitations of surgical implantation due to its cost effective and user friendly nature.