Arun Prabhu Rameshbabu

A biodegradable, biocompatible transdermal device derived from carboxymethyl cellulose and multi-walled carbon nanotubes for sustained release of diclofenac sodium

A hybrid nanocomposite hydrogel (CMC–MWCNT) has been fabricated using carboxymethyl cellulose (CMC) and acid-functionalized multi-walled carbon nanotubes (MWCNTs) at room temperature for transdermal delivery of diclofenac sodium. With variation of MWCNT concentration, various grades of nanocomposites have been prepared and an optimized composite (CMC–MWCNT 3) has been considered with lower % swelling and higher gel strength. The synthesized nanocomposite has been characterized using FTIR spectroscopy, FESEM, TGA, AFM and TEM analyses. The gel strength of the nanocomposites has been measured by determining the rheological parameters. The biodegradability of the composite material has been confirmed using lysozyme hydrochloride. A biocompatibility study using primary rat fibroblasts (RFBs) confirmed the non-cytotoxic nature of the composite. The release profiles of diclofenac sodium indicate that the synthesized composite releases the drug in a sustained manner and would be a better alternative for transdermal devices.

Covalent cross-links in polyampholytic chitosan fibers enhances bone regeneration in a rabbit model

Chitosan fibers were prepared in citric acid bath, pH 7.4 and NaOH solution at pH 13, to form ionotropically cross-linked and uncross-linked fibers, respectively. The fibers formed in citric acid bath were further cross-linked via carbodiimide chemistry; wherein the pendant carboxyl moieties of citric acid were used for new amide bond formation. Moreover, upon covalent cross-linking in the ionically gelled citrate-chitosan fibers, incomplete conversion of the ion pairs to amide linkages took place resulting in the formation of a dual network structure. The dual cross-linked fibers displayed improved mechanical property, higher stability against enzymatic degradation, hydrophobicity and superior bio-mineralization compared to the uncross-linked and native citrate cross-linked fibers. Additionally, upon cyclic loading, the ion pairs in the dual cross-linked fibers dissociated by dissipating energy and reformed during the relaxation period. The twin property of elasticity and energy dissipation mechanism makes the dual cross-linked fiber unique under dynamic mechanical conditions. The differences in the physico-chemical characteristics were reflected in protein adsorption, which in turn influenced the cellular activities on the fibers. Compared to the uncross-linked and ionotropically cross-linked fibers, the dual cross-linked fibers demonstrated higher proliferation and osteogenic differentiation of the MSCs in vitro as well as better osseous tissue regeneration in a rabbit model.

Dextrin and poly(lactide)-based biocompatible and biodegradable nanogel for cancer targeted delivery of doxorubicin hydrochloride

Herein, we report the development and application of a novel biocompatible, chemically crosslinked nanogel for use in anticancer drug delivery. The nanogel [n-Dxt-p(lactide)] has been synthesized from dextrin and poly (lactide) by in situ crosslinking with a homobifunctional crosslinker through a conventional radical polymerization technique. The properties of the nanogel have been investigated using FTIR spectroscopy, 1H NMR spectroscopy, TGA, FESEM, TEM and DLS. The stimuli responsiveness of the nanogel has been detected by measuring its pH dependent swelling in different buffer solutions at 37 ± 0.5 °C. It was found that the size of nanogel was less than 10 nm. Degradation experiments using hen egg lysozyme revealed that the nanogel is biodegradable. In vitro cytocompatibility studies against human mesenchymal stem cell (hMSCs) suggested that the nanogel is non-toxic. The nanogel can efficiently load and encapsulate doxorubicin hydrochloride (Dox) within the matrix with 28.26 ± 0.20% loading efficiency and 91.16 ± 0.64% encapsulation efficiency. Additionally, the native nanogel showed non-toxic effects on MG 63 cancer cells, while Dox-loaded nanogel demonstrated high toxicity towards cancer cells. Because of its very small size, the nanogel can effortlessly enter into the cell cytoplasm and destroy cancer cells. The n-Dxt-p(lactide) nanogel released doxorubicin in a sustained manner and appears to be a high-quality option for doxorubicin hydrochloride delivery.

2,5-Dimethoxy 2,5-dihydrofuran crosslinked chitosan fibers enhance bone regeneration in rabbit femur defects

Chitosan fibers were fabricated via pH induced neutralization and precipitation in a 5 w/v% NaOH bath. Intermolecular covalent crosslinking of these fibers were performed through imine linkages between the glucosamine units of polymers and the dialdehyde groups of 2,5-dimethoxy-2,5-dihydrofuran at 60 °C, pH 2.2. The covalently crosslinked fibers demonstrated improved tensile strength, stiffness, hydrophobicity and higher stability against enzymatic degradation compared to uncrosslinked ones under wet conditions. The differences in the physico-chemical characteristics were reflected in protein adsorption which in turn facilitated higher cellular proliferation and adhesion to the crosslinked fibers. Osteogenesis of human bone marrow derived mesenchymal stem cells (hMSCs) was significantly higher on crosslinked fibers compared to the uncrosslinked ones as evidenced by higher alkaline phosphatase expression, calcium deposition and osteocalcin secretion. In vivo study performed subcutaneously in a rabbit model with crosslinked fibers revealed its ability to integrate with host tissues and showed differential extent of cellular infiltration and extracellular matrix production after specified periods of implantation. Further bone regeneration ability at the defect site filled with crosslinked fibers was evident by histological analysis. Thus, the study suggests that the imine crosslinked fibers could be used for bone tissue engineering applications.

Citrate cross-linked gels with strain reversibility and viscoelastic behavior accelerate healing of osteochondral defects in a rabbit model.

Most living tissues are viscoelastic in nature. Self-repair due to the dissipation of energy by reversible bonds prevents the rupture of the molecular backbone in these tissues. Recent studies, therefore, have aimed to synthesize biomaterials that approximate the mechanical performance of biological materials with self-recovery properties. We report an environmentally friendly method for the development of ionotropically cross-linked viscoelastic chitosan gels with a modulus comparable to that of living tissues. The strain recovery property was found to be highest for the gels with the lowest cross-linking density. The force-displacement curve showed significant hysteresis due to the presence of reversible bonds in the cross-linked gels. Nanoindentation studies demonstrated the creep phenomenon for the cross-linked chitosan gels. Creep, hysteresis, and plasticity index confirmed the viscoelastic behavior of the cross-linked gels. The viscoelastic gels were implanted at osteochondral defect sites to assess the tissue regeneration ability. In vivo results demonstrated early cartilage formation and woven bone deposition for defects filled with the gels compared to nontreated defects.

Critical issues in near net shape forming via green machining of ceramics: A case study of alumina dental crown

Abstract Green machining of ceramics through Computer Numerical Control (CNC) is efficient for near net shape fabrication due to minimum consumption of energy, less tool wear, and high material removal rate. However, there are numerous critical issues need to be addressed while manufacturing customized components through green state machining including fabrication of machinable green ceramics, designing of suitable mold for slurry casting, manufacture of suitable sample holders for mounting the fragile green samples during machining, and designing of machining tools for good surface finishing. This article introspects these critical issues and its possible solutions for efficient fabrication of dental crowns as a case study via green state machining. Highly loaded (55 vol%) alumina slurry was prepared for the fabrication of machinable dense alumina compacts by Protein Coagulation Casting (PCC) technique. Cylindrical alumina compacts were fabricated by casting alumina slurry into the polyvinyl chloride (PVC) mold. Metallic cylindrical sample holder was fabricated for mounting the green alumina samples for CNC machining. Diamond impregnated tool (∼3 mm diameter) was used for near net shaping of dental crown by grinding/milling. Dental crown (incisor) was successfully fabricated by optimizing different machining parameters.

Stimuli-responsive, biocompatible hydrogel derived from glycogen and poly(N-isopropylacrylamide) for colon targeted delivery of ornidazole and 5-amino salicylic acid

In the present article, a novel biocompatible and stimuli-responsive hydrogel (cl-Gly/pNIPAm) has been fabricated through free radical polymerisation using biopolymer glycogen (Gly), N-isopropylacrylamide (NIPAm) monomer and ethylene glycol dimethacrylate (EGDMA) crosslinker. Several grades of hydrogels have been developed and an optimized grade (i.e. c-Gly/NIPAm 4 with higher % crosslinking) has been used for characterisation and application towards colon targeted drugs carrier. The temperature and pH sensitivity of the cl-Gly/pNIPAm hydrogel have been studied by assessing equilibrium swelling at 25/37 °C and pH 1.2/7.4. The LCST of the developed hydrogel has been determined and found to be in the range of 32.5–34 °C. The degradation kinetics of the hydrogel has been performed. The hydrogel demonstrates good compatibility towards human mesenchymal stem cells (hMSCs). It is degraded by hen egg lysozyme. The synthesized hydrogel can load colon targeted drugs, 5-amino salicylic acid (5-ASA) and ornidazole, efficiently and released both drugs in a controlled manner, while ∼96–97% of drugs remained stable after 2 months. The release kinetics and mechanism have also been studied.

Investigating the potential of human placenta-derived extracellular matrix sponges coupled with amniotic membrane-derived stem cells for osteochondral tissue engineering

Osteochondral injuries are challenging to repair due to their complex tissue anatomy and restricted self-repairing ability associated with a limited blood supply. Osteochondral tissue engineering is an important clinical aspect of the management and treatment of cartilage and underlying bone. In the present study, we fabricated human placenta-derived extracellular matrix sponges (PEMS) for repair of osteochondral tissue through a decellularization process. There were no significant cellular components present in the PEMS; hematoxylin & eosin/DAPI staining, DNA quantification and agarose gel electrophoresis were used to evaluate the extent of decellularization. Moreover, no significant alteration to the collagen and glycosaminoglycan (native extracellular matrix) content of the PEMS was observed. PEMS in vitro provided a non-cytotoxic environment rich in bioactive cues for human amniotic membrane-derived stem cells (HAMSCs) to proliferate in and differentiate into chondrogenic and osteogenic lineages under induction. Histological analysis at 28 days after the PEMS were subcutaneously implanted demonstrated no severe immune response in the host and supported the formation of blood vessels. To assess the osteochondral tissue repair ability of PEMS, cell-free PEMS (CFP) and cell-seeded PEMS (CSP) were implanted at osteochondral defect sites in a rabbit model. Histological scores indicated that osteochondral regeneration was more successful in the defects filled with CSP compared to those filled with CFP and empty defects (ED) after 60 days of implantation. In summary, a naturally derived biocompatible scaffold composed of extracellular matrix from human placenta has been successfully developed for osteochondral tissue engineering.

Chitosan Derivatives Cross-Linked with Iodinated 2,5-Dimethoxy-2,5- dihydrofuran for Non-Invasive Imaging

Radiopaque polymer derivatives were successfully prepared through surface diffusion mediated cross-linking of chitosan with iodinated 2,5-dimethoxy-2,5-dihydrofuran. The incorporation of iodine in 2,5-dimethoxy-2,5-dihydrofuran was validated by (1)H NMR and mass spectroscopy. The cross-linking of the glucosamine moieties of chitosan with the iodinated product was confirmed by (13)C NMR and energy-dispersive X-ray spectroscopy. Radiography analysis proved inherent opacity of the iodinated fibrous sheets and microspheres that were comparable to the X-ray visibility of aluminum hollow rings of equivalent thickness and commercially available radiopaque tape, respectively. Microscopic studies evidenced retention of the fiber/microsphere morphology after the iodination/cross-linking reactions. The effects of iodination/cross-linking on the mechanical and biodegradation properties of fibers were studied by nanoindentation and enzymatic assay, respectively. In vitro and in vivo studies established the nontoxic, biodegradable nature of radiopaque derivatives. Iodinated fiber mesh implanted in a rabbit model was significantly X-ray opaque compared to the uncross-linked fiber mesh and medical grade surgical swabs. Further, opacity of the iodinated mesh was evident even after 60 days, though the intensity was reduced, which indicates the biodegradable nature of the iodinated polymer. The opacity of the iodinated sutures was also established in the computed tomography images. Finally, the sufficient in vivo contrast property of the radiopaque microspheres in the gastrointestinal tract indicates its possible role in clinical diagnostics.

Accelerated healing of full thickness dermal wounds by macroporous waterborne polyurethane-chitosan hydrogel scaffolds

Wound healing is a dynamic process wherein cells, and macromolecules work in consonance to facilitate tissue regeneration and restore tissue integrity. In the case of full-thickness (FT) wounds, healing requires additional support from native or synthetic matrices to aid tissue regeneration. In particular, a matrix with optimum hydrophilic-hydrophobic balance which will undergo adequate swelling as well as reduce bacterial adhesion has remained elusive. In the present study, polyurethane diol dispersion (PUD) and the anti-bacterial chitosan (Chn) were blended in different ratios which self-organized to form macroporous hydrogel scaffolds (MHS) at room temperature on drying. SEM and AFM micrographs revealed the macroporosity on top and fracture surfaces of the MHS. FTIR spectra revealed the intermolecular as well as intra-molecular hydrogen bonding interactions between the two polymers responsible for phase separation, which was also observed by micrographs of blend solutions during the drying process. The effect of phase separation on mechanical properties and in vitro degradation (hydrolytic, enzymatic and pH dependent) of MHS were studied and found to be suitable for wound healing. In vitro cytocompatibility was demonstrated by the proliferation of primary rat fibroblast cells on MHS. Selected MHS was subjected to in vivo FT wound healing study in Wistar rats and compared with an analogous polyurethane containing commercial dressing i.e. Tegaderm™. The MHS-treated wounds demonstrated accelerated healing with increased wound contraction, higher collagen synthesis, and vascularization in wound area compared to Tegaderm™. Thus, it is concluded that the developed MHS is a promising candidate for application as FT wound healing dressings.