Biology subjects

Bajaj, M.

Publications and source records attributed to Bajaj, M..

3 recordsLinked to original sources

bioRxiv2021

Nano-hydroxyapatite coating synthesized on quasi-fibrillar superstructures of collagen hydrolysate leads to superior osteoblast proliferation when compared to nano-hydroxyapatite synthesized on collagen fibrils

This study had a two-fold objective: To utilize collagen hydrolysate for synthesizing a nanoscale Hydroxyapatite (HA) coating that would act as a superior osteoblast adhesion/proliferation agent compared to collagen-derived HA (C/HA) and to comprehend the significant role played by structural constraints on HA nucleation. Collagen was extracted from pacu skin with a high yield of 65.3% (w/w of tissue). It was digested by collagenase and the hydrolysate (CH) was purified with a high yield of 0.68g/g of collagen. The CH peptides had a mass of 6kDa, a predominant PP-II conformation and formed self-assembling hierarchical structures at physiological pH with dimensions of 842.2{+/-}229nm. The HA synthesized on CH (CH/HA) displayed higher yield when compared to C/HA. Structural analysis of CH/HA revealed that the PP-II peptides coiled to form mimic-helical moieties with reduced intermolecular packing distance of 0.9nm. The mimic helices cross-linked to form a vast quasi-fibrillar network that was comparatively smaller than collagen fibrils but exhibited enhanced stability and greater dynamicity. CH/HA displayed intense calcium-carboxyl interactions, sharper diffraction planes, smaller size of 48{+/-}6.2nm and a Ca/P ratio closer to 1.69 when compared to C/HA along with displaying serrated edge blooming crystals. Because of the small size, the CH/HA nanocrystals displayed significantly better osteoblast adhesion than C/HA and reduced the doubling time of cells. Overall, the results indicated that CH based nanocomposites displayed suitable morphological characteristics and cellular response for potential application as implant and bone graft coating material. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/431097v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@1b020c2org.highwire.dtl.DTLVardef@36a899org.highwire.dtl.DTLVardef@77106aorg.highwire.dtl.DTLVardef@d6b801_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2021

Contribution of quasi-fibrillar superstructures in peroxide quenching by collagen peptides derived from fish processing by-products and their application as natural food additives

This study attempts to identify the significant role played by the secondary structure of collagen-derived peptides that are involved in lipid peroxide quenching in food products. Collagen was extracted from the skin of Perch and swim bladder of Rohu at 45-78% efficiency. It was identified as type-I based on a high molecular weight (110kDa) and its ion-exchange elution profile. The collagen samples were enzymatically hydrolyzed and collagen hydrolysate (CH) was extracted with an efficiency of 0.67-0.74g/g of collagen. The CH samples displayed a molecular weight in the range of 8.2-9.7kDa and exhibited a higher abundance of charges resulting in higher solubility. The structural studies revealed that the CH peptides existed in polyproline-II helix and formed a mimic-triple helix in a wide range of pH. In neutral and alkaline pH, the mimic helices joined to form a hierarchical quasi-fibrillar network that was smaller than collagen fibrils but also more dynamic. The CH exhibited >95% degradation in 15h through simulated digestion. The CH were able to decrease peroxide formation by 84.5-98.9% in commercially available cod liver and almond oil and increased the shelf life of soya bean oil by a factor of 5 after 6 months of storage. The addition of CH to cultured cells quenched peroxide ions generated in situ and decreased stressor activity by a factor of 12. The reason behind the high efficacy of CH was deciphered to be the proximal charge stabilization by the quasi-fibrillar network, which allowed efficient peroxide quenching and long-term stability.

biochemistry↗

bioRxiv2020

A fully defined pluripotent stem cell derived multi-liver-cell model for steatohepatitis and fibrosis

Chronic liver injury, as observed in non-alcoholic steatohepatitis (NASH), progressive fibrosis, and cirrhosis, remains poorly treatable. Steatohepatitis causes hepatocyte loss in part by a direct lipotoxic insult, which is amplified by derangements in the non-parenchymal cellular (NPC) interactive network wherein hepatocytes reside, including, hepatic stellate cells, liver sinusoidal endothelial cells and liver macrophages. To create an in vitro culture model encompassing all these cells that allows studying liver steatosis, inflammation and fibrosis caused by NASH, we here developed a fully defined hydrogel microenvironment, termed hepatocyte maturation (HepMat) gel, that supports maturation and maintenance of pluripotent stem cell (PSC)-derived hepatocyte- and NPC-like cells for at least one month. The HepMat-based co-culture system modeled key molecular and functional features of TGF{beta}-induced liver fibrosis and fatty-acid induced inflammation and fibrosis better than monocultures its constituent cell populations. The novel co-culture system should open new avenues for studying mechanisms underlying liver steatosis, inflammation and fibrosis as well as for assessing drugs counteracting these effects.

bioengineering↗