Fabrication of GelMA - Agarose Based 3D Bioprinted Photocurable Hydrogel with In Vitro Cytocompatibility and Cells Mirroring Natural Keratocytes for Corneal Stromal Regeneration.

The complex anatomy of the cornea and the subsequent keratocyte-fibroblast transition have always made corneal stromal regeneration difficult. Recently, 3D printing has received considerable attention in terms of fabrication of scaffolds with precise dimension and pattern. In the current work, 3D printable polymer hydrogels made of GelMA/agarose are formulated and its rheological properties are evaluated. Despite the variation in agarose content, both the hydrogels exhibited G'>G'' modulus. A prototype for 3D stromal model is created using Solid Works software, mimicking the anatomy of an adult cornea. The fabrication of 3D-printed hydrogels is performed using pneumatic extrusion. The FTIR analysis speculated that the hydrogel is well crosslinked and established strong hydrogen bonding with each other, thus contributing to improved thermal and structural stability. The MTT analysis revealed a higher rate of cell proliferation on the hydrogels. The optical analysis carried out on the 14th day of incubation revealed that the hydrogels exhibit transparency matching with natural corneal stromal tissue. Specific protein marker expression confirmed the keratocyte phenotype and showed that the cells do not undergo terminal differentiation into stromal fibroblasts. The findings of this work point to the potential of GelMA/A hydrogels as a novel biomaterial for corneal stromal tissue engineering.

Poly (lactic acid)/ amine grafted mesoporous silica-based composite for food packaging application.

The present study focuses on the development of environmentally friendly bio-composite films using poly(lactic acid) (PLA) as a biopolymer matrix. This is achieved by incorporating amine functionalized green mesoporous silica (GMS) and employing a solution casting method for film fabrication. The motivation behind the work is to improve the compatibility between PLA and green mesoporous silica sourced from rice husk by functionalizing GMS with APTES (3-Aminopropyltriethoxy silane). The primary objective is to explore how the inclusion of GMS influences both the physicochemical attributes and the efficacy of active food packaging in PLA. The introduction of GMS to the PLA matrix not only improves the flexibility of PLA/GMS composite films but also enhances their overall performance. The reinforcement of GMS in the PLA matrix has also significantly contributed towards the reduction in oxygen transmittance rate and provided an anti-bacterial effect towards pathogen i.e. S. aureus and E. coli. The PLA/GMS composite films exhibit antioxidant activity acting as potential scavengers with around 78 % efficacy against DPPH (2,2-diphenyl-1-picrylhydrazyl). Consequently, the PLA/GMS composite formulation proposed in this study shows promising outcomes in terms of strength, flexibility, antioxidant properties, and antibacterial characteristics. Also, the PLA/GMS films extended the shelf life of cut apple samples for seven days.

3D bioprinted photo crosslinkable GelMA/methylcellulose hydrogel mimicking native corneal model with enhanced in vitro cytocompatibility and sustained keratocyte phenotype for stromal regeneration.

Corneal transplantation serves as the standard clinical therapy for serious corneal disorders. However, rejection of grafts, significant expenditures, and most crucially, the global donor shortage, may affect the outcome. Recently, 3D bioprinting using biodegradable polymeric materials has become a suitable method for creating tissue replicas with identical architecture. One such most renowned material is GelMA, for its scaffold's three-dimensional structure, biocompatibility, robust mechanics, and favourable optical transmittance. However, GelMA's inadequate viscosity to print at body temperature with better form integrity remains an obstacle. The aim of this work is to create 3D printed GelMA/MC hydrogels for corneal stroma tissue engineering using MC's printability at room temperature and GelMA's irreversible photo cross-linking with UV irradiation. The print speed and pressure conditions for 3D GelMA/MC hydrogels were tuned. Thermal, morphological and physicochemical characteristics were studied for two distinct concentrations of GelMA/MC hydrogels. The hydrogels achieved a transparency of ~78 % (at 700 nm), which was on par with that of the normal cornea (80 %). The in vitro studies conducted using goat corneal stromal cells demonstrated the ability of both hydrogels to promote cell adhesion and proliferation. Expression of Vimentin and keratan sulphate validated the phenotype of keratocytes in the hydrogel. This 3D printed GelMA/MC hydrogel model mimics biophysical characteristics of the native corneal stroma, which may hold promise for clinical corneal stromal tissue engineering.

Poly(lactic acid)/cholecalciferol based composites for active food packaging application.

Poly(lactic acid) (PLA) based sustainable composites incorporated with cholecalciferol (Vitamin D3) (CC) at different concentrations (1, 3, 5 and 10 wt%) were prepared using solvent casting method. Performance analysis of PLA/CC composite films in terms of food packaging properties like thermal, optical, oxygen barrier, mechanical, anti-bacterial as well as anti-oxidant effect is carried out. The PLA/CC-5 composite showed complete blockage of UV-B light at 320 nm, which is known to significantly induce the photo-chemical degradation of polymers. The incorporation of CC in the PLA matrix brought in improvement in mechanical and oxygen barrier properties. The PLA composite films showed effective antibacterial activity against food borne bacteria (S. aureus and E. coli), in addition to excellent antioxidant activity. All these important traits exhibited by PLA/CC composite films suggest its potential for food packaging application.

3D bioprinted poly(lactic acid)/mesoporous bioactive glass based biomimetic scaffold with rapid apatite crystallization and in-vitro Cytocompatability for bone tissue engineering.

In the recent years, bone tissue engineering is regarded as the promising solution for treatment of bone defects which arises due to trauma, infection and surgical intervention. In view of this, several polymer or ceramic based constructs are envisaged for bone tissue engineering potential. However, scaffolds based on pure polymeric materials suffer from slow bioactivity characteristics. On the other hand, scaffolds based on ceramic materials do not offer sufficient strength for load bearing applications. In order to overcome these drawbacks, the current work aims to develop mixed matrix scaffolds based on poly (L-lactic acid)/mesoporous bioactive glass composite with the formulation of 30:70 weight ratio, which mimics the natural bone composition. In the current work, PLA/MBG (30:70) composite based bioink suitable for 3D bioprinting is indigenously developed and its rheological characteristics are evaluated. The 3D architecture for PLA/MBG composite scaffold is designed using Solidworks CAD 2015 and the scaffolds are fabricated using pneumatic based 3D bioprinting technology, which has not been documented earlier for this formulation in view of bone tissue engineering in the best of our knowledge. Followed by this, optimization of printing parameters in order to develop 3D PLA/MBG composite constructs with hierarchical pore architecture suitable for bone tissue engineering is performed. The SEM analysis confirmed that the pore size of the 3D printed PLA/MBG composite scaffolds falls in the range of 500-700 µm, which corresponds to the macroporous nature of the scaffolds useful for bone cell growth. The mechanical analysis confirmed the superior compressive modulus and yield strength for PLA/MBG composite scaffold in comparison with neat PLA. The in-vitro bioactivity assessment showed rapid apatite crystallization by attaining Ca/P ratio of 1.66 equivalent to natural bone mineral within 3rd day of SBF treatment for PLA/MBG composite scaffold, thus indicating the excellent bioactivity behaviour. The 3D bioprinted PLA/MBG composite scaffold showed promising response in terms of cell attachment and proliferation, mineralization as well as gene expression characteristics while assessed through of in-vitro biological assessment using MG-63 osteosarcoma cells. In this regard, the 3D bioprinted PLA/MBG scaffold could be applied as potential implant for bone tissue engineering application.

Investigating the properties of poly (lactic acid)/exfoliated graphene based nanocomposites fabricated by versatile coating approach.

In order to overcome the challenges that underlies in dispersion of exfoliated graphene (GR) into poly lactic acid (PLA) matrix by extrusion, a versatile approach is used in this work, where uniform coating of GR over PLA is carried out prior to extrusion of PLA. Effect of melt processing on different graphene loaded composites (PLA-M-0.05GR, PLA-M-0.2GR) is studied. Investigation on the morphology, thermal stability, crystallization property, surface wettability, mechanical property, and dynamic mechanical property of composites are performed. XRD analysis and morphological analysis confirm the formation of well dispersed composite. Thermo-gravimetric analysis and kinetic study reveal significant improvement in thermal stability. Improvement in crystallinity, melting point, crystallization point are found from DSC analysis. Crystallization kinetic study is carried out and nucleation effect of the GR on crystallization of PLA chain is noticed. Hydrophobicity of the PLA composites is increased by the incorporation of graphene. Tensile strength of the composites is noticed to be increased as compared to PLA-M. An improvement of storage modulus for the composites over PLA-M is observed by Dynamic mechanical analysis.

UV protective poly(lactic acid)/rosin films for sustainable packaging.

Recently, biopolymer based plastic materials are regarded as potential alternative for conventional plastics of fossil fuel origin in order to compensate depleting petroleum resources and address environmental pollution issues. Poly(lactic acid) (PLA) is one among the biopolymers which is rapidly commercialized for food packaging application. However, the demerits accompanied with PLA like brittle nature, slower crystallization rate, poor gas barrier and high ultraviolet radiation transmission properties confines its commercial application in food packaging sector. Studies on the improvement of ductility, crystallization rate and gas barrier properties are markedly reported. Much emphasis is not given in the literature on improving UV shielding properties which plays important role in preventing oxidation degradation of PLA. Therefore, the current work is focused on fabrication of eco-friendly poly(lactic acid)/rosin (RS) based biocomposite films with improved UV shielding along with ductility and oxygen barrier properties. The PLA-RS biocomposite films containing different loadings (1, 3, 5, 10 and 20wt%) of RS with an average thickness of 50µm are fabricated via solution casting technique. The PLA-RS film demonstrated noteworthy light barrier feature by shielding the passage of ∼98%, 92% and 53% in UV-B, UV-A and visible light regime, respectively. In case of UV-C region, complete blockage of UV transmission through the PLA-RS biocomposite film is noticed. In addition to this, the presence of RS in the PLA matrix brought considerable improvement in terms of ductility and oxygen barrier characteristics. This in turn indicates PLA-RS biocomposite films hold significant potential for sustainable food packaging application.

Hydrolytic degradation behaviour of sucrose palmitate reinforced poly(lactic acid) nanocomposites.

This work discusses the influence of novel biofiller, "sucrose palmitate" (SP) on the hydrolytic degradation behavior of poly(lactic acid) (PLA) nanocomposites. The influence of temperature and pH of the solution on the hydrolytic degradation behavior of PLA and PLA-SP nanocomposites was investigated. The variation in the crystallinity of PLA and PLA composites subjected to the hydrolytic degradation process is verified by XRD and DSC analysis. The morphological changes that occurred during the degradation process are observed by scanning electron microscopy (SEM). Thermo-gravimetric analysis confirms the loss of thermal stability of the neat PLA as well as composites after hydrolytic degradation process. Transparency measurements support the enhancement in opacity of both the PLA and PLA-SP nanocomposites with progress in hydrolytic degradation period.