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Polymer composites fabricated using plant fibers have become a dominant role in number of industries due to the outstanding results of their physical and mechanical characteristics when compared to traditional materials. The current study aims to develop lightweight and affordable composite materials using Cyperus pangorei fiber (CPF) and a vinyl ester (VE) resin matrix. Comparing the characteristics of composite materials created with different fiber lengths (3 to 11 mm) and contents (10 to 50% weight). The composite with 7mm fiber length and 40% of fiber content demonstrated the highest level of stability among the various fiber weight and lengths percentages tested. A composite system's fiber contents have a significant impact on its overall performance. The bonding of fibers and matrix of the specimens were good, according to SEM analysis. As a result, the current study suggests that the optimal CPFreinforced VE composites would be a capable substitute to traditional materials for value-added engineering products. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) bioprinting has emerged as a revolutionary technology for constructing functional tissue equivalents/scaffolds for tissue engineering applications. Bioink design is a crucial element in 3D bioprinting, which typically comprises a mixture of biomaterials, biological molecules or cells followed by its printing and tissue maturation. An ideal bioink should possess suitable physicochemical, mechanical, rheological, and biological features of the target tissue. However, mimicking multifaceted compositions similar to native extracellular matrix (ECM) with bioactive milieu of soluble and non-soluble factors is challenging. Herein, we report the formulation and characterization of a bioink system, comprising methacrylamide modified gelatin (GelMA) and 2-hydroxylpropyl methacrylate (HPMA) with a cost-effective redox initiators based cross-linking. GelMA was synthesized by reacting gelatin with methacrylic anhydride (MA) and subsequently, copolymerized with HPMA at room temperature by redox mechanism. Various hydrogel formulations by varying GelMA: HPMA w/v% ratios (G:HP) were studied as 10:0 (G100HP0), 9.5:0.5 (G95HP05), 9:1 (G90HP10), 8:2 (G80HP20), and 6:4 (G60HP40), to identify the best bioink composition. The formulations were characterized for its opacity, chemical, rheological, mechanical, porosity and swelling properties and cytocompatibility as per ISO-10993 standards. Cell encapsulation studies using live/dead assay analyzed cell viability inside the handprinted and 3D printed constructs. The preliminary results indicate successful formulation of cytocompatible bioink for potential 3D bioprinting and biofabrication applications.

Tissue-engineered skin with mechanical and biological properties that match the native tissue could be a valuable graft to treat non-healing chronic wounds. Fibroblasts grown on a suitable biodegradable scaffold are a feasible strategy for the development of a dermal substitute above which epithelialization may occur naturally. Cell growth and phenotype maintenance are crucial to ensure the functional status of engineered tissue. In this study, an electrospun biodegradable polymer scaffold composed of a terpolymer PLGC [poly(lactide-glycolide-caprolactone)] with appropriate mechanical strength was used as a scaffold so that undesirable contraction of the wound could be prevented when it was implanted. To enhance cell growth, synthetic PLGC was incorporated with a fibrin-based biomimetic composite. The efficacy of the hybrid scaffold was evaluated by comparing it with bare PLGC in terms of fibroblast growth potential, extracellular matrix (ECM) deposition, polymer degradation, and mechanical strength. A significant increase was observed in fibroblast attachment, proliferation, and deposition of ECM proteins such as collagen and elastin in the hybrid scaffold. After growing fibroblasts for 20 d and 40 d, immunochemical staining of the decellularized scaffolds showed deposition of insoluble collagen and elastin on the hybrid scaffold but not on the bare scaffold. The loss of mechanical strength consequent to in vitro polymer degradation seemed to be balanced owing to the ECM deposition. Thus, tensile strength and elongation were better when cells were grown on the hybrid scaffold rather than the bare samples immersed in culture medium. Similar patterns of in vivo and in vitro degradation were observed during subcutaneous implantation and fibroblast culture, respectively. We therefore postulate that a hybrid scaffold comprising PLGC and fibrin is a potential candidate for the engineering of dermal tissue to be used in the regeneration of chronic wounds.

Porous and pliable conduits made of biodegradable polymeric scaffolds offer great potential for the development of blood vessel substitutes but they generally lack signals for cell proliferation, survival and maintenance of a normal phenotype. In this study we have prepared and evaluated porous poly(ε-caprolactone) (PCL) integrated with fibrin composite (FC) to get a biomimetic hybrid scaffold (FC PCL) with the biological properties of fibrin, fibronectin (FN), gelatin, growth factors and glycosaminoglycans. Reduced platelet adhesion on a human umbilical vein endothelial cell-seeded hybrid scaffold as compared to bare PCL or FC PCL was observed, which suggests the non-thrombogenic nature of the tissue-engineered scaffold. Analysis of real-time polymerase chain reaction (RT-PCR) after 5 days of endothelial cell (EC) culture on a hybrid scaffold indicated that the prothrombotic von Willebrand factor and plasminogen activator inhibitor (PAI) were quiescent and stable. Meanwhile, dynamic expressions of tissue plasminogen activator (tPA) and endothelial nitric oxide synthase indicated the desired cell phenotype on the scaffold. On the hybrid scaffold, shear stress could induce enhanced nitric oxide release, which implicates vaso-responsiveness of EC grown on the tissue-engineered construct. Significant upregulation of mRNA for extracellular matrix (ECM) proteins, collagen IV and elastin, in EC was detected by RT-PCR after growing them on the hybrid scaffold and FC-coated tissue culture polystyrene (FC TCPS) but not on FN-coated TCPS. The results indicate that the FC PCL hybrid scaffold can accomplish a remodeled ECM and non-thrombogenic EC phenotype, and can be further investigated as a scaffold for cardiovascular tissue engineering.

A major constraint in the use of biodegradable polymer scaffolds for vascular tissue engineering is poor cell adhesion and lack of signals for new tissue generation. The presence of extracellular matrix (ECM) within the scaffold is desirable for growth of endothelial cells and in vitro formation of remodelled vascular conduit. In this study, we have produced a hybrid scaffold by coating porous poly-caprolactone (PCL) film with biomimetic ECM components consisting of fibrin, gelatin, fibronectin, angiogenic growth factors and proteoglycans. Human umbilical vein endothelial cells (HUVECs) adhered, spread, proliferated and survived for long periods in culture on the hybrid scaffold. As compared to bare PCL, enhanced cell adhesion, spreading and cytoskeletal organization were demonstrated on the hybrid scaffold, using confocal microscopy of EC-actin stained with Texas red-conjugated phalloidin. Population doubling of endothelial cells (ECs) on the hybrid scaffold and bare scaffold was estimated as 42 h and 136 h, respectively, as assessed by a 3H-thymidine uptake method. Analysis of proliferating cell nuclear antigen (PCNA) also indicated low proliferation on bare scaffold. Flow cytometric analysis of annexin V-stained cells showed poor survival of ECs on bare PCL as compared to the hybrid scaffold. Deposition of insoluble collagen and elastin was identified on the hybrid scaffold by cells recovered after 15 days and 30 days of EC culture, using fluorochrome-tagged specific antibodies and confocal microscopy, and the fluorescence intensity corresponding to elastin and collagen after 30 days was similar to that of 15 days. The results indicate that ECM deposition by endothelial cells is a regulated process without excessive accumulation after 30 days., (Copyright (c) 2007 John Wiley & Sons, Ltd.)

Three light curing composite pastes with varying resin matrix ratios [bisphenol A-glycidyl methacrylate (BIS-GMA)/urethane tetramethacrylate (UTMA) 25:75, BIS-GMA/UTMA 50:50, and BIS-GMA/UTMA 75:25 w/w%] were prepared in combination with a radiopaque glass powder and camphorquinone photoinitiator. Cured samples were aged at 37 degrees C in three food simulating media such as citrate buffer (pH 4.0), PBS buffer (pH 7.4), and 75% ethyl alcohol. Samples were withdrawn at specific intervals of 1, 15, 30, 45, and 60 days and tested for changes in mechanical properties, sorption, and solubility characteristics. Statistical calculations revealed significant changes in compressive strength (CS) for composites depending on the resin matrix ratio and type of medium used for aging. While diametral tensile strength (DTS) was affected adversely in citrate medium for composites with higher urethane content, samples stored in alcohol medium showed deterioration of transverse strength (TS) and microhardness (VMH) for all composites studied. Increase in BIS-GMA content in the resin matrix and storage in alcohol medium resulted in higher sorption and solubility values and lower microhardness.

After the development of a two-paste chemical cure composite, evaluation of its physicochemical properties, toxicological evaluation and in-vivo experiments in dogs teeth with histopathological study of dental tissues, a clinical trial was carried out and commercial production recommended. As the shelf life of the material was not enough, a light cure composite was developed, its material characteristics, toxiclological study, in-vivo experiments in dogs with histopathological evaluation and clinical trials carried out. However, the material was radiolucent, and could not be seen in an x-ray and differentiated from a cavity after filling was done. This led to the development of radiopaque light cure composite. Compressive strength, diametral strength, and microhardness were tested with 200-250 phr range of incorporated radiopaque glass particle filler of the size 0.7 to 1.0 micron this improved the properties when compared to conventional composites. The composite was non-toxic and suitable for animal studies. In vivo studies are underway in dogs with histopathological studied of the pulp and dentin. The material awaits clinical trials prior to commercial production.

Progressive three body wear up to 30 min for five dental composites (Concise, Heliomolar, Occlusin, P-30, Profile, TPH) stored for 9 months at 37 degrees C in citrate, lactate and PBS buffers, 25 and 75% ethanol media, has been measured using a wear tester. Particle size of the filler and the storage media are found to play dominant roles in determining the extent of wear. Heliomolar, which is a microfilled composite, shows maximum wear whereas wear is least in composites containing filler particles of conventional and hybrid size such as P-30 (> 1 micron). The storage media is found to attack and degrade glass filler particles compared to composites having quartz fillers.

Four long-chain aliphatic organic diluents, triethylene glycol dimethacrylate (TEGDMA), ethylene glycol dimethacrylate (EDMA), triethyleneglycol diacrylate (TEGDA) and tetraethylene glycol diacrylate (TTEGDA) were used as diluents for preparing a visible-light-cured dental composite. Cured samples of pastes prepared using the above diluents were stored separately for a period of 60 days in distilled water at 37 degrees C and tested for changes in compressive strength, diametral tensile strength and microhardness at specific intervals of 1, 7, 14, 21, 28 and 60 days. Samples prepared using TEGDMA showed better strength values initially compared with the composite specimens prepared using the rest of the diluents although they are found to deteriorate slowly upon storage in distilled water up to 60 days. Samples prepared using EDMA showed retention in properties whereas samples prepared using TEGDA and TTEGDA showed large deviations in strength values during the first 28 days, did not deteriorate further and were found either to show improvement upon ageing or to remain constant. Sorption values seem to reach a maximum for all composites and then to decrease further after 14 days whereas solubility is found to increase with time.

The purpose of this study was to evaluate the reactivity and the effect of concentration of three tertiary amines upon the mechanical properties of a chemical curing dental composite. Chemical cured composite pastes were prepared by keeping peroxide concentration constant at 1 wt% (by weight of resin mixture) and by varying the amine/peroxide molar ratio from 0.25 to 1.5. Composite samples were prepared for all three amine pastes aged for 1, 15, 30, 45, and 60 d stored at 8, 22, and 37 degrees C. The loss in activity of the tertiary amine with time was measured. Changes in compressive strength, diametral tensile strength, and microhardness were also measured. A sharp decrease in working and setting times corresponding to increased activity was noticed with an increased amine content. The activity was found to vary in the order N,N-dimethyl p-toluidine (DMPT) > 2-(4-dimethylaminophenyl)ethanol (DMAPEA) > N,Ndiethanol p-toluidine (DEPT). DMPT is found to be more temperature sensitive than DMAPEA and DEPT. However, DEPT is found to provide better storage stability out of all three amines tested. Each amine was found to possess optimum concentrations at which the mechanical properties showed maximum values. DEPT is preferred for long-term storage stability in chemical-cured dental composites where aging tends to reduce the activity of the amine.

Two paste, self cured BIS-GMA based resin was developed and physicochemical and biological characterization carried out. Its suitability and safety for clinical use were evaluated. Clinical trials for direct bonding of Orthodontic brackets conducted at the College of Dental Surgery, Manipal showed a success rate of 83% against 85% with "Right On" adhesive used as control. Further research to improve shelf life of the material led to the development of light cure-BIS-GMA based resin. It was evaluated for physicochemical characteristics which included setting time, compressive strength, diametral tensile strength, microhardness, water sorption and exothermic reaction. Biological characterization studies on material toxicity and biocompatibility on animal models established the safety and suitability of this composite for clinical use in dentistry. Clinical evaluation for direct bonding of Orthodontic brackets in comparison to Ultralight (T.P Orthodontics, USA) showed its handling characteristics to be superior to control. Flash removal was easier around bracket bases bonded with Chitra light cure. However, bond strength of light cure composite was 66% as compared to 79% with Ultralight. Subsequent improvement of the material increased the bond strength significantly. Failure rate with the new material was 11% against 13% with control in the ongoing clinical trials.

The objective of this investigation was twofold: 1) to determine the extent of microleakage associated with two visible light cured dental composites, one of which is an indigenously developed light cure composite (chitra light cure system) compared with a commercially available control material (Prisma APH light cure system), and 2) to study the effect of using bonding agents upon the above phenomena. The bonding agents used along with the above composites during restoration were chitra bonding agent system containing chitra primer/chitra resin and a control (Probond) which was purchased commercially. A comparison of microleakage in freshly restored human premolar teeth by silver nitrate staining technique was made during the above study. Cavities were restored with both composites with and without bonding agents, stored in 50 percent silver nitrate, and sections were cut after developing. The microtomed sections were observed under the optical light microscope and scanning electron microscope. Results indicate that bonding agents are mandatory for effective bonding at the tooth/resin interface and subsequent reduction in marginal leakage. Chitra bonding agent showed excellent adhesive bonding characteristics at the dentine/composite interface with minimal marginal leakage compared to the control bonding system. The chitra light cure composite material also showed lower shrinkage characteristics compared to Prisma APH composite.

Synolite resin was analysed using FTIR, NMR and HPLC to determine its components and purity. The resin was found to be predominantly BIS-GMA containing traces of its two isomers. The analysis indicated that there was no unreacted methacrylic acid or other impurities.

The grafting of N-vinyl pyrrolidone, a hydrophilic monomer, on to flexible poly(vinyl chloride) sheets used in medical applications using ionizing radiation from a 60Co source was studied. The graft yield was found to increase linearly with monomer concentration and also with increasing radiation doses. The migration of the plasticizer di-(2-ethylhexyl)phthalate into a strong organic extractant such as n-hexane was studied at different time intervals for different grafted systems of poly(vinyl chloride) at 30 degrees C. The results indicated a drastic reduction in the leaching of the plasticizer from grafted systems versus ungrafted controls. Incorporation of ethylene dimethacrylate cross-linker during grafting did not seem to affect the graft yield considerably but appeared to further reduce the plasticizer migration. Surface energy calculations of the grafted samples indicate that the surfaces are highly hydrophilic compared to ungrafted poly(vinyl chloride) and the polar and dispersion components tend to vary with increasing cross-linker concentration.