Drug/bioactive eluting chitosan composite foams for osteochondral tissue engineering.

Joint defects associated with a variety of etiologies often extend deep into the subchondral bone leading to functional impairment and joint immobility, and it is a very challenging task to regenerate the bone-cartilage interface offering significant opportunities for biomaterial-based interventions to improve the quality of life of patients. Herein drug-/bioactive-loaded porous tissue scaffolds incorporating nano-hydroxyapatite (nHAp), chitosan (CS) and either hydroxypropyl methylcellulose (HPMC) or Bombyx mori silk fibroin (SF) are fabricated through freeze drying method as subchondral bone substitute. A combination of spectroscopy and microscopy (Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), and X-ray fluorescence (XRF) were used to analyze the structure of the porous biomaterials. The compressive mechanical properties of these scaffolds are biomimetic of cancellous bone tissues and capable of releasing drugs/bioactives (exemplified with triamcinolone acetonide, TA, or transforming growth factor-ß1, TGF-ß1, respectively) over a period of days. Mouse preosteoblast MC3T3-E1 cells were observed to adhere and proliferate on the tissue scaffolds as confirmed by the cell attachment, live-dead assay and alamarBlue™ assay. Interestingly, RT-qPCR analysis showed that the TA downregulated inflammatory biomarkers and upregulated the bone-specific biomarkers, suggesting such tissue scaffolds have long-term potential for clinical application.

Bi-layered α-tocopherol acetate loaded membranes for potential wound healing and skin regeneration.

With an increase in the demand for skin regeneration products, there is a noticeable increase in developing materials that encourage, wound healing and skin regeneration. It has been reported that antioxidants play an important role in anti-inflammatory reactions, cellular proliferation and remodeling phase of wound healing. While consideration all these factors, a novel α-tocopherol acetate (vitamin E) (VE) loaded bi-layered electrospun membrane, based on lower polycaprolactone (PCL) layer and upper polylactic acid (PLA) layer, was fabricated through electrospinning. Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), in-vitro degradation studies, swelling studies and VE release studies were performed to evaluate structural, physical and in-vitro behavior of membranes. Biological properties of membranes were evaluated through cell proliferation assay, cell adhesion studies, live/dead cell assay and CAM assay. SEM images showed that the average diameter of nanofibers ranged from 1 to 6 µm, while addition of VE changed the diameter and morphology of fibers. Bi-layered membranes showed significant swelling behavior through water uptake, membranes loaded with 30% VE showed 8.7% and 6.8% degradation in lysozyme and H2O2 respectively. 20% and 30% VE loaded membranes followed Korsmeyer-Peppas and first order drug release kinetics followed by non-fickian drug release kinetics. Membranes showed non-toxic behavior and supported cell proliferation via alamar blue assay, cell adhesion via SEM, cell viability via live/dead assay and wound healing by scratch assay. CAM assay showed that membranes having VE supported angiogenesis and showed significant formation of blood vessels making it suitable for skin regeneration and wound healing. Results showed that large surface area of nanofibers, porous structure and biocompatible nature are suitable for targeted clinical applications.

Effect of nano-bioceramics on monomer leaching and degree of conversion of resin-based composites.

The aim of this laboratory study was to evaluate the monomer leaching and degree of conversion (DC) from experimental bioactive resin composites (RBCs) and to do comparison with commercial bulkfill and packable resin composites. Experimental dimethacrylatebased resin composites were reinforced with silanated nano-hydroxyapatite (30 and 45 wt%). The ion leaching and DC of these resin composites were compared and contrasted with SDR™ and Filtek P60™ by using the high performance liquid chromatography (HPLC) and Fourier transform infrared spectroscopy (FTIR), respectively. A significant difference was found in elution of monomer between the resin composites. SDR™ showed significantly high monomer elution and structural changes compared to other resin composites. The DC of bioactive RBCs showed the highest conversion rate after polymerization. Resin composite with nano-hydroxyapatite with the presence of a bioactive component might provide biomimetic approach for the material. Moreover, a low concentration of nanohydroxyapatite nano-fillers have shown better properties than micro-fillers based resin composites.

Hydroxypropylmethyl cellulose (HPMC) crosslinked chitosan (CH) based scaffolds containing bioactive glass (BG) and zinc oxide (ZnO) for alveolar bone repair.

The success of a dental implant relies on the presence of an optimal alveolar ridge. The aim of this study was to fabricate HPMC crosslinked chitosan based scaffolds for alveolar bone repair. Our results indicated that HPMC crosslinked CH/BG foams presented better morphological structure (132-90.5 µm) and mechanical responses (0.451 MPa with 100 mg BG) as confirmed by SEM analysis and fatigue testing respectively. Cytotoxicity analysis at day 2, 4 and 8 demonstrated that all composites were non-toxic and supported cellular viability. Calcein AM/propidium iodide staining, Hoechst nuclear staining and cell adhesion assay reiterated that scaffolds supported pre-osteoblast cell growth, adhesion and proliferation. Differentiation potential of pre-osteoblast cells was enhanced as confirmed by alkaline phosphate assay. Furthermore, loss of S. aureus viability as low as 35% was attributed to synergistic effects of components. Overall, our results suggest that HPMC crosslinked scaffolds are potential candidates for alveolar bone repair.

Chitosan/hydroxyapatite (HA)/hydroxypropylmethyl cellulose (HPMC) spongy scaffolds-synthesis and evaluation as potential alveolar bone substitutes.

Alveolar bone loss is associated with infections and its augmentation is a pre-requisite for the success of dental implants. In present study, we aim to develop and evaluate novel freeze dried doxycycline loaded chitosan (CS)/hydroxyapatite (HA) spongy scaffolds where hydroxypropylmethyl cellulose (HPMC) was added as a crosslinker. Scaffolds displayed compressive strength of 14MPa/cm3 and 0.34 as elastic response. The interconnected pore diameter was 41-273µm, favorably provided the template supporting cells and transport. An overall 10% degradation was seen after 14day's studies at pH 7.4 in PBS. Doxycycline hyclate, a frequently used drug to counter oral infections, demonstrated an initial burst release (6-8h), followed by a sustain release profile for the remaining 64h. CS/HA/HPMC scaffolds were nontoxic and promoted pre-osteoblast cell viability as seen with live/dead calcein staining after 24h where scaffolds with 10% and 25% HPMC by weight of scaffold had more viable cells. Scaffolds with 10%, 20% and 25% HPMC by weight of scaffold showed efficient cellular adhesion as seen in scanning electron microscopy images (day 8) indicating that pre-osteoblast cells were able to adhere well on the surface and into the porous structure via cytoplasmic extensions. Hoechst 33258 nuclear staining at day 2 and 8 indicated cell proliferation which was further supported byMTT assay at day 2, 4 and 8. Although all scaffolds supported pre-osteoblast cell viability, alkaline phosphatase (ALP) staining demonstrated that upon induction, differentiation was pronounced in case of scaffolds with 10% HMPC scaffolds. Conclusively, these materials having all the required mechanical and biological properties are potential candidates for alveolar bone regeneration.

2-(4-Acetamido-benzene-sulfonamido)-3-methyl-butanoic acid.

In the title compound, C(13)H(18)N(2)O(5)S, the benzene ring and the acetamide group are almost coplanar [dihedral angle = 5.6 (3)°], and the amine group projects almost vertically from this plane [C-C-S-N = -84.5 (7)°]. A short intra-molecular C-H⋯O contact occurs. In the crystal, O-H⋯O, N-H⋯O and N-H⋯(O,O) hydrogen bonds lead to a three-dimensional network. One of the methyl groups of the isopropyl residue is disordered over two orientations in a 0.747 (16):0.253 (16) ratio.

2-(2,5-Dichloro-benzene-sulfonamido)-3-methyl-butanoic acid.

The structure of the title compound, C(11)H(13)Cl(2)NO(4)S, shows one sulfonamide-O atom to lie almost in the plane of the benzene ring [C-C-S-O = -178.7 (2) °] and the other to one side [C-C-S-O = -49.4 (3)°]. Lying to the other side is the amine residue, which occupies a position almost perpendicular to the plane [C-S-N-C = 70.2 (2)°]; the carb-oxy-lic acid group is orientated to lie over the benzene ring. In the crystal, the appearance of an 11-membered {⋯OH⋯OCOH⋯OC(2)NH} synthon, which features the hy-droxy group forming both donor (to a carbonyl-O) and acceptor (from the amine-H) inter-actions, leads to the formation of a supra-molecular chain along the a axis. Chains are connected in the crystal structure by C-H⋯O contacts.