Abstract: Porous tri-calcium phosphate, well-known for its use as artificial bone, was prepared via sponge polymeric method by the application of low cost polyurethane (PU) foam as a structural guide. In this experiment, fractions of tri-calcium phosphate (TCP) are controlled at 12, 13, 14, 15 and 16 grams and mixed with distilled water (fixed at 25 grams) to produce slurries. Subsequently, rectangular shaped PU foam was immersed in the slurry and dried for three days. Samples were then sintered at 1100°C to obtain porous tri-calcium phosphate. This method produces porous tri-calcium phosphate with porosity between 31-44% and the compressive strength in the range of 0.17-1.02 MPa. The macroporosity of the tri-calcium phosphate, observed through SEM, was in the range of 100 µm to 900 µm.
Abstract: A novel tissue engineered construct was used to engineer skeletal muscle tissue for reconstruction of abdominal wall defects, which is a common challenge to surgeons, due to insufficient autogenous tissue. Myoblasts were isolated from soleus muscle fibers, seeded onto the scaffold and cultivated in vitro for 5 days. Full-thickness abdominal wall defects (3 x 4 cm) were created in 18 male New Zealand white rabbits and randomly divided into two equal groups (n=9 each). The defects of the first group were repaired with myoblast seeded bovine pericardium (treatment group) whereas the second group involved non-seeded bovine pericardium (control group). Three animals were sacrificed at 7, 14, and 30 days post-implantation from each group and the explanted specimens were subjected to macroscopic, light, fluorescence and electron microscopic analysis. In each case, the tissue engineered construct was thicker from deposition of newly formed collagen with neo-vascularisation, than the control group. Most importantly, multinucleated myotubes and myofibers were only detected in the treatment group. Therefore, this study demonstrates that myoblast-seeded bovine pericardium construct can provide a structural replacement for severe and large abdominal wall defects with profound regeneration of skeletal muscle tissues.
Abstract: Gum Arabica, an Electro-Active Bio-Polymer (EABP) is employed to develop photosensitive bio-complexes with chromophore matter collected from natural flowers and chlorophyll from plant leaves. The photosensitivity and enhancement of electro-activity of the developed complex and nano-cluster doped specimens of the same are examined experimentally. The electrical, optical, and photoelectrical characteristics are also investigated experimentally. It has been observed that the electrical property is mostly mixed conducting and can be tailored. The photo electrical behaviour is found to be fascinating. The developed complex is capable of absorbing light by losing or gaining electrons. The application potential of the developed complex toward light harvesting processes is exploited to develop a non-silicon based solar cell. The electrical characteristics of the developed solar cells are studied. The results obtained are good when compared to those of existing solar cells.
Abstract: Research on fog harvesting for drinking water is uncommon because it is not a continuous climatic phenomenon and concerns only arid and semi-arid regions abundant with fog. This paper proposes a new biomimetic-inspired method of harvesting fog by mimicking the skin of the Namib desert beetle. Stainless steel mesh panels are subjected to ultra shortening and annealing to create a hierarchical nano/micro hybrid surface, and an emulsion of PTFE, polyvinyl acetate and sodium benzene sulfonate is sprayed over the steel mesh. This produces hydrophilic nano/micro mounts and hydrophobic troughs. This method, although initially costly, offers a sustainable fog collecting system which can be adopted for arid and semi-arid regions of Pakistan and other similar regions.
Abstract: This review presents a discourse on challenges in understanding and imitating the process of amelogenesis in vitro on the molecular scale. In light of the analysis of imitation of the growth of dental enamel, it also impends on the prospects and potential drawbacks of the biomimetic approach in general. As the formation of enamel proceeds with the protein matrix guiding the crystal growth, while at the same time conducting its own degradation and removal, it is argued that three aspects of amelogenesis need to be induced in parallel: a) crystal growth; b) protein assembly; c) proteolytic degradation. A particular emphasis is therefore placed on ensuring conditions for proteolysis-coupled protein-guided crystallization to occur. Discussed are structural and functional properties of the protein species involved in amelogenesis, mainly amelogenin and enamelysin, the main protein and the protease of the developing enamel matrix, respectively. A model of enamel growth based on controlled delivery of constituent ions or crystalline or amorphous building blocks by means of amelogenin is proposed. The importance of high viscosity of the enamel matrix and a more intricate role that water may play in such a gelatinous medium are also touched upon. The tendency of amelogenin to self-assemble into fibrous and rod-shaped morphologies is considered as potentially important in explaining the formation of elongated apatite crystals. The idea that a pre-assembling protein matrix serves as a template for the uniaxial growth of apatite crystals in enamel is finally challenged with the one based on co-assembly of the protein and the mineral phases.
Abstract: Tissue engineering will play an increasingly vital role in cancer research. Provision of biomimetic microenvironment systems for in vitro cancer models can be addressed in part by utilizing thick 3D scaffolds with high interconnective porosity . This approach gives rise to new analytical challenges and opportunities. In this preliminary study, Variotis™ synthetic scaffolds of high interconnected porosity and hierarchical structure were used. An effective macroscopic porosity of 94.3 ±1.74 vol% was attained by using microCT and finite element methods. The actual porosity was determined to be 94.6±0.29 vol%. Scaffolds were compressed in a customized jig to thicknesses of 99.5 mm, 74.6 mm, 46.3 mm (±0.5% tolerance) and then annealed to set respective porosities of 94.3 vol%, 93.2 vol%, 89.5 vol% (±1.5% tolerance). Scaffolds were then sectioned to 2mm thickness. DLD-1 colon cancer cells were grown on 3D scaffolds of three specified porosities for varying periods of time then imaged using confocal and scanning electron microscopy methods. Hoechst staining resulted with minimal scaffold autofluoresence while autofluoresence exceeded useful limits when used in conjunction with Alexa488-phalloidin under argon laser excitation in confocal microscopy. Using Hoechst staining, DLD-1 cells (nuclei) were observed to readily attach and proliferate on Variotis™ scaffolds. Normal DLD-1 cell morphologies were evident using scanning electron microscopy. The high interconnected porosity of the scaffolds allowed cells to be observed deep within scaffolds. Scaffolds remained structurally stable and unified throughout all culture experiments and provided ease of handling during cell culture and microscopy.
Abstract: A series of linear poly(2-hydroxyethyl methacrylate) (PHEMA) with defined molecular weights (MW) and narrow molecular distributions were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization using cumyl dithiobenzoate (CDB) as a chain transfer agent. Murine fibroblasts (3T3) were exposed to eluates from various PHEMA samples, washed or unwashed, and with or without dithioester end groups. After 72 hrs in cell culture, no cytotoxic response was elicited by the polymer samples devoid of dithioester end groups, and which also underwent a thorough washing regime. Specimens throughout the entire MW range were internalized by a macrophage (cell line Raw 264), suggesting that such polymers can be used as models for studying the biodegradation of PHEMA.