Stability Of Collagen Research Articles

Tunable Stress Relaxing Biomimetic Matrices: Hyaluronan/Hydroxyapatite Hybridization Mediates Assembly of Collagen Fibrils.

The alluring correlations of cellular behaviors with viscoelastic extracellular matrices have driven increasing endeavors directed toward the understanding of mechanical cues on cell growth and differentiation via preparing biomimetic scaffolds/gels with viscoelastic controllability. Indeed, systematic investigations, especially into calcium phosphate-containing biomimetics, are relatively rare. Here, oxidized hyaluronic acid/hydroxyapatite hybrids (OHAHs) were synthesized by hyaluronan-mediated biomimetic mineralization with confined ion diffusion and subsequent oxidization treatment. The collagen self-assembly was applied to fabricate tunable stress relaxing fibrillar matrices in the presence of OHAHs in which the incorporated hyaluronic acid with aldehyde groups acted to improve the component compatibility as well as to supplement the molecular interactions with the occurrence of a Schiff-base reaction. With the addition of varying OHAH contents, the self-assembly behavior of collagen was altered, and the obtained collagen-hybrid (CH) matrices presented a heterogeneous fibrillar structure interspersed with OHAHs, characterized by large fibrillar bundles coexisting with small fibrils. The OHAHs improved the hydrogel stability of pure collagen, and according to rheological and nanoindentation measurements, CH matrices also exhibited tunable stress relaxation rates, following an OHAH concentration-dependent fashion. The proliferation and spreading of MC3T3-E1 cells cultured onto such CH matrices were further found to increase with the stress relaxing rate of the matrices. The present study showed that the introduction of hydroxyapatite incorporated with active hyaluronic acid during collagen reconstitution was a simple and effective strategy to realize the preparation of tunable stress relaxing biomimetic matrices potentially used for further appraising the regulation of mechanical cues on cell behaviors.

Collagen IV of basement membranes: IV. Adaptive mechanism of collagen IV scaffold assembly in Drosophila

Collagen IV is an essential structural protein in all metazoans. It provides a scaffold for the assembly of basement membranes, a specialized form of extracellular matrix, which anchors and signals cells and provides microscale tensile strength. Defective scaffolds cause basement membrane destabilization and tissue dysfunction. Scaffolds are composed of α-chains that coassemble into triple-helical protomers of distinct chain compositions, which in turn oligomerize into supramolecular scaffolds. Chloride ions mediate the oligomerization via NC1 trimeric domains, forming an NC1 hexamer at the protomer-protomer interface. The chloride concentration-"chloride pressure"-on the outside of cells is a primordial innovation that drives the assembly and dynamic stabilization of collagen IV scaffolds. However, a Cl-independent mechanism is operative in Ctenophora, Ecdysozoa, and Rotifera, which suggests evolutionary adaptations to environmental or tissue conditions. An understanding of these exceptions, such as the example of Drosophila, could shed light on the fundamentals of how NC1 trimers direct the oligomerization of protomers into scaffolds. Here, we investigated the NC1 assembly of Drosophila. We solved the crystal structure of the NC1 hexamer, determined the chain composition of protomers, and found that Drosophila adapted an evolutionarily unique mechanism of scaffold assembly that requires divalent cations. By studying the Drosophila case we highlighted the mechanistic role of chloride pressure for maintaining functionality of the NC1 domain in humans. Moreover, we discovered that the NC1 trimers encode information for homing protomers to distant tissue locations, providing clues for the development of protein replacement therapy for collagen IV genetic diseases.

Sustainable antibacterial collagen composites with silver nanowires for resistive pressure sensor applications

Considering the circular economy and the increasing need of smart materials for the digitalization of society, it is essential that these materials are based on bio-resources. Thus, in order to replace synthetic by natural polymers in multifunctional composites, this work reports on the development of collagen/silver nanowires (Ag NWs) composites for resistive sensor applications. It is demonstrated the physical interactions of hydroxyl groups in collagen with the Ag NWs and that the Ag NWs are well dispersed within the collagen matrix. Further, the addition of Ag NWs to the collagen matrix increases the thermal stability of collagen and the Ag NW content does not affect the triple helix structure of the polymer matrix. The mechanical, electrical and antibacterial properties depend on Ag NW content and the best electric conductivity of 0.0515 S cm−1 is obtained for composites with 6 wt% of Ag NWs. This composite presents suitable resistance variations under pressure and bending allowing the development of sustainable multifunctional sensing composites with antibacterial activity that can be applied in next generation touch sensing electronic devices.

Proton Transport Across Collagen Fibrils and Scaffolds: The Role of Hydroxyproline.

Collagen is one of the most studied proteins due to its fundamental role in creating fibrillar structures and supporting tissues in our bodies. Accordingly, collagen is also one of the most used proteins for making tissue-engineered scaffolds for various types of tissues. To date, the high abundance of hydroxyproline (Hyp) within collagen is commonly ascribed to the structure and stability of collagen. Here, we hypothesize a new role for the presence of Hyp within collagen, which is to support proton transport (PT) across collagen fibrils. For this purpose, we explore here three different collagen-based hydrogels: the first is prepared by the self-assembly of natural collagen fibrils, and the second and third are based on covalently linking between collagen via either a self-coupling method or with an additional cross-linker. Following the formation of the hydrogel, we introduce here a two-step reaction, involving (1) attaching methanesulfonyl to the -OH group of Hyp, followed by (2) removing the methanesulfonyl, thus reverting Hyp to proline (Pro). We explore the PT efficiency at each step of the reaction using electrical measurements and show that adding the methanesulfonyl group vastly enhances PT, while reverting Hyp to Pro significantly reduces PT efficiency (compared with the initial point) with different efficiencies for the various collagen-based hydrogels. The role of Hyp in supporting the PT can assist in our understanding of the physiological roles of collagen. Furthermore, the capacity to modulate conductivity across collagen is very important to the use of collagen in regenerative medicine.

Insight into the synthesis of biocompatible polymer for collagen stabilization and leather process

Collagen-based biomaterials are highly effective owing to their high biocompatibility and non-immunogenicity, but their biological application is still constrained because of poor thermal stability. The greener crosslinkers devoid of aldehydes and toxic precursors have recently evoked considerable interest. In this work, biocompatible and multifunctional carboxyl polymer (MCP) has been synthesized by a simple one-step carboxylation reaction by modifying the hydroxyl group in the monomer, followed by polymerization in aqueous conditions. The synthesized polymer has been used for both collagen stabilization and leather processing. The circular dichroism studies revealed a significant change in the secondary structure of the collagen with increasing concentration of the MCP, and thermal stability of the rat tail tendon is enhanced up to 70 °C. The application of MCP as a crosslinker for collagen in the leather-making process along with metal salts increased the leather's thermal stability and improved uptake of the metal salts. The interaction mechanism of MCP and the metals during the tanning process is through complexation with carboxyl pendants available on the MCP backbone, as confirmed by UV–Visible and IR spectroscopy. The experimental leathers showed a uniform penetration of tanning agents and excellent mechanical properties compared to the control leathers. Further, biocompatibility studies using 3 T3 fibroblast cells revealed that the MCP did not induce any significant cytotoxicity with cell viability of 96%, confirming the non-toxic nature of the synthesized polymer. Thus, the current study opens a new path for sustainable alternative polymeric crosslinkers for collagen stabilization and its potential application in biomaterial and leather-making fields.

Effects of proanthocyanidins and dialdehyde chitosan on the proliferation and differentiation of bovine myoblast for cultured meat production

Cultured meat technology intends to manufacture meat by cultivating muscle stem cells in vitro, which is an emerging methodology in meat production. However, the insufficient stemness of bovine myoblasts cultivated in vitro declined the ability of cell expansion and myogenic differentiation, which limited the production of cultured meat. Therefore, in this study, we introduced proanthocyanidins (PC, natural polyphenolic compounds) and dialdehyde chitosan (DAC, natural polysaccharides) to explore the effects of proliferation and differentiation of bovine myoblasts in vitro. The experiment results revealed that PC and DAC promoted cell proliferation by improving the transition from G1 to the S phase as well as cell division in G2. Meanwhile, the myogenic differentiation of cells was further boosted by the combined PC and DAC up-regulation of MYH3 expression. Moreover, the study revealed the synergistic effect of PC and DAC on enhancing the structural stability of collagen, and bovine myoblasts demonstrated excellent growth and dispersion ability on collagen scaffolds. It is concluded that both PC and DAC promote the proliferation and differentiation of bovine myoblasts, contributing to the development of cultured meat production systems.

Structural and functional properties of collagen isolated from lumpfish and starfish using isoelectric precipitation vs salting out.

The possibility of replacing the very time and resource demanding salting out (SO) method with isoelectric precipitation (IP) during collagen extraction from common starfish and lumpfish was investigated. The effect of IP on yield, structural and functional properties of the collagens was therefore compared with SO. Application of IP resulted in a higher or similar collagen mass yield compared with SO from starfish and lumpfish, respectively. However, the purity of collagens recovered with IP was lower than those recovered with SO. Replacing SO with IP did not affect polypeptide pattern and tropohelical structural integrity of collagen from the two resources as revealed with SDS-PAGE and FTIR analysis. Thermal stability and fibril formation capacity of collagens recovered with IP were also well preserved. Overall, the results showed that the IP can be a promising resource smart alternative for the classic SO precipitation during collagen extraction from marine resources.

Consequences of incorporating thiaproline and its oxidized derivatives into collagen triple helices.

(2R)-4-thiaproline (Thp) is an analog of proline, replacing Cγ in the pyrrolidine ring with sulfur. Its thiazolidine ring easily interconverts between endo and exo puckers due to a small energy barrier, which leads to destabilize polyproline helices. Collagen, composed of three polyproline II helices, mainly consists of X-Y-Gly triplets, where X is often proline and Y is frequently (2S,4R)-hydroxyproline. In this study, we incorporated Thp into either position-X or position-Y to investigate the consequences of such a replacement on the triple helix. Circular dichroism and differential scanning calorimetry analyses showed that the Thp-containing collagen-mimetic peptides (CMPs) can fold into stable triple helices, in which the substitution at position-Y exhibits a larger destabilization effect. Additionally, we also prepared the derivative peptides by oxidizing Thp in the peptide to N-formyl-cysteine or S,S-dioxide Thp. The results showed that the oxidized derivatives at position-X only slightly affect collagen stability, but those at position-Y induce a large destabilization effect. The consequences of incorporating Thp and its oxidized derivatives into CMPs are position dependent. Computational results suggested that the ease of interconversion between exo and endo puckers for Thp and the twist conformation of S,S-dioxide Thp may cause the destabilization effect at position-Y. We have revealed new insights into the impacts of Thp and its oxidized derivatives on collagen and demonstrated that Thp can be used to design collagen-related biomaterials.

Effect of chitosan-oleuropein nanoparticles on dentin collagen cross-linking.

The integrity and stability of collagen are crucial for the dentin structure and bonding strength at dentin-resin interface. Natural plant-derived polypehenols have been used as collagen crosslinkers. The aims of the study were to develop novel chitosan oleuropein nanoparticles (CS-OL-NPs), and to investigate the CS-OL-NPs treated dentin's the resistance to enzymatic degradation and mechanic property. CS-OL-NPs were developed using the ionotropic gelation method. Release and biocompatibility of the CS-OL-NPs were tested. Twenty demineralized dentin collage specimens were randomized into four interventions groups: A, Deionized Water (DW); B, 5% glutaraldehyde solution (GA); C, 1 mg/ml chitosan (CS); and D, 100 mg/L CS-OL-NPs. After 1-min interventions, dentin matrix were evaluated by the micro-Raman spectroscopy for the modulus of elasticity test. Collagen degradation was assessed using hydroxyproline (HYP) assay. CS-OL-NPs were spherical core-shape with a size of 161.29 ± 8.19 nm and Zeta potential of 19.53 ± 0.26 mV. After a burst release of oleuropein in the initial 6 h, there was a long-lasting steady slow release. CS-OL-NPs showed a good biocompatibility for the hPDLSCs. The modulus of elasticity in the crosslinked groups were significantly higher than that in the control group (P< 0.05 for all). The specimens treated with CS-OL-NP showed a greater modulus of elasticity than those treated with GA and CS (P< 0.05 for both). The release of HYP in the crosslinked group was significantly lower than that in the non-crosslinked groups (P< 0.05 for all). CS-OL-NPs enhanced the dentin mechanical property and resistance to biodegradation, with biocompatibility and potential for clinical application.

Circadian clock molecule REV-ERBα regulates lung fibrotic progression through collagen stabilization

Molecular clock REV-ERBα is central to regulating lung injuries, and decreased REV-ERBα abundance mediates sensitivity to pro-fibrotic insults and exacerbates fibrotic progression. In this study, we determine the role of REV-ERBα in fibrogenesis induced by bleomycin and Influenza A virus (IAV). Bleomycin exposure decreases the abundance of REV-ERBα, and mice dosed with bleomycin at night display exacerbated lung fibrogenesis. Rev-erbα agonist (SR9009) treatment prevents bleomycin induced collagen overexpression in mice. Rev-erbα global heterozygous (Rev-erbα Het) mice infected with IAV showed augmented levels of collagens and lysyl oxidases compared with WT-infected mice. Furthermore, Rev-erbα agonist (GSK4112) prevents collagen and lysyl oxidase overexpression induced by TGFβ in human lung fibroblasts, whereas the Rev-erbα antagonist exacerbates it. Overall, these results indicate that loss of REV-ERBα exacerbates the fibrotic responses by promoting collagen and lysyl oxidase expression, whereas Rev-erbα agonist prevents it. This study provides the potential of Rev-erbα agonists in the treatment of pulmonary fibrosis.

Designing Collagen-Binding Peptide with Enhanced Properties Using Hydropathic Free Energy Predictions.

Collagen is fundamental to a vast diversity of health functions and potential therapeutics. Short peptides targeting collagen are attractive for designing modular systems for site-specific delivery of bioactive agents. Characterization of peptide-protein binding involves a larger number of potential interactions that require screening methods to target physiological conditions. We build a hydropathy-based free energy estimation tool which allows quick evaluation of peptides binding to collagen. Previous studies showed that pH plays a significant role in collagen structure and stability. Our design tool enables probing peptides for their collagen-binding property across multiple pH conditions. We explored binding features of currently known collagen-binding peptides, collagen type I alpha chain 2 sense peptide (TKKTLRT) and decorin LRR-10 (LRELHLNNN). Based on these analyzes, we engineered a collagen-binding peptide with enhanced properties across a large pH range in contrast to LRR-10 pH dependence. To validate our predictions, we used a quantum-dots-based binding assay to compare the coverage of the peptides on type I collagen. The predicted peptide resulted in improved collagen binding. Hydropathy of the peptide-protein pair is a promising approach to finding compatible pairings with minimal use of computational resources, and our method allows for quick evaluation of peptides for binding to other proteins. Overall, the free-energy-based tool provides an alternative computational screening approach that impacts protein interaction search methods.

Thermal stability of sea cucumber collagen and effects of gallic acid crosslinking

SummaryThe thermal processing characteristics of sea cucumber collagen (SCC) are closely related to its triple helix structure, self‐assembly and aggregation ability. The effect of heat treatment on SCC was studied by apparent viscosity, circular dichroism spectra and so on. As heating time increased from 10 to 160 min, apparent viscosity decreased from 400 to 300 mPa·s at 80 °C, indicating the structure of SCC changed. The decrease in SCC self‐assembly and aggregation ability showed the structural change. Positive peak at 220 nm was decreased from 24 to 0 mdeg at 60 °C for 10–160 min, which revealed that SCC triple helix structure was uncoiled and disappeared. Fluorescence intensity was increased and the absorption peak showed a red shift during thermal treatment. Gallic acid crosslinking could improve thermal stability and inhibit the degradation of collagen. It could provide theoretical guidance for sea cucumber processing.

Micro-Raman spectroscopy analysis of dentin remineralization using eggshell derived nanohydroxyapatite combined with phytosphingosine

The aim of this study was to assess the remineralization efficacy of chicken eggshell–derived nano-hydroxyapatite (CEnHAp) combined with phytosphingosine (PHS) on artificially induced dentinal lesions. PHS was commercially procured whereas CEnHAp was synthesized using microwave-irradiation method and characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high-resolution scanning electron microscopy–energy-dispersive X-ray spectroscopy (HRSEM-EDX), and transmission electron microscopy (TEM). A total of 75 pre-demineralized coronal dentin specimens were randomly treated with one of the following test agents (n = 15 each): artificial saliva (AS), casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), CEnHAp, PHS, and CEnHAp-PHS under pH cycling for 7, 14, and 28 days. Vickers microhardness indenter, HRSEM-EDX, and micro-Raman spectroscopy methods were used to assess the mineral changes in the treated dentin samples. Data were submitted to Kruskal–Wallis and Friedman's two-way analyses of variance (p < 0.05). HRSEM and TEM analysis depicted irregular spherical structure of the prepared CEnHAp with a particle size of 20–50 nm. The EDX analysis confirmed the presence of Ca, P, Na and Mg ions. The XRD pattern showed the characteristic crystalline peaks for hydroxyapatite and calcium carbonate that are present in the prepared CEnHAp. Dentin treated with CEnHAp-PHS revealed highest microhardness values along with complete tubular occlusion compared to other groups at all test time intervals (p < 0.05). Specimens treated with CEnHAp showed increased remineralization than those treated with CPP-ACP followed by PHS and AS groups. The intensity of mineral peaks, as observed in the EDX and micro-Raman spectra, confirmed these findings. Further, the molecular conformation of the collagen's polypeptide chains, and amide-I and CH2 peaks attained peak intensities in dentin treated with CEnHAp–PHS and PHS whereas other groups revealed poor stability of collagen bands. Microhardness, surface topography, and micro-Raman spectroscopy analyses revealed that dentin treated with CEnHAp–PHS have an improved collagen structure and stability as well as highest mineralization and crystallinity.

Mussel-inspired polymer with catechol and cationic Lys functionalities for dentin wet bonding.

Mussels can form tough and long-lasting adhesions to organic and inorganic surfaces in saline and impactive severe aquatic environments. Similar to mussel adhesion, dentin bonding occurs in a wet environment. However, unlike mussels, it is difficult to achieve long-lasting bonds with dentin. Moreover, water is considered a major hindrance in dentin bonding. Inspired by the synergistic effect of cationic lysine (Lys) and catechol on the elimination of the hydration layer during mussel adhesion, a catechol- and Lys-functionalized polymerizable polymer (catechol-Lys-methacrylate [CLM]) was synthesized to replicate the complex synergy between amino acids and catechol. The bond-promoting potential of 5​mg/mL CLM primer was confirmed using an in vitro wet dentin-bonding model, which was characterized by an improvement in bond strength and durability. CLM can adhere to wet demineralized dentin, with Lys acting as a molecular vanguard to expel water. Subsequently, a myriad of interfacial interactions can be obtained by introducing the catechol group into the interface. Additionally, tough and long-lasting adhesion, similar to that formed by mussels, can be achieved by grafting CLM onto type I collagen via covalent bonds, hydrogen bonds, Van der Waals interactions, and cation-π interactions, which can enhance the mechanical and chemical stability of collagen, increase the enzymatic resistance of collagen, and provide additional physical/chemical adhesion to dentin bonds. Catechol- and cationic Lys-functionalized polymers can improve the stability of the resin-dentin interface under wet conditions.

Characterization of Type I and Type III Collagen in the Intramuscular Connective Tissue of Wuzhumuqin Sheep.

Intramuscular connective tissue (IMCT) collagen is an important factor in meat quality. This study analyzed the characteristics of type I and III collagen in the IMCT of the semitendinosus (SD) and longissimus dorsi (LD) of Wuzhumuqin sheep at different growth stages (6, 9, 12, and 18 months). Utilizing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared spectroscopy (FTIR), collagen types I and III were successfully isolated and shown to contain an intact triple helix structure. Immunofluorescence revealed that these collagens were located in the endomysium and perimysium. Collagen-related genes were significantly expressed in sheep aged 9 and 12 months. The amino acid content increased with age in type I collagen whereas it decreased in type III collagen. Furthermore, type III collagen contained more hydroxyproline (Hyd) than type I collagen. Differential scanning calorimetry (DSC) revealed that the thermal stability of collagen increased with age, accompanied by a decrease in solubility. Semitendinosus muscle had more collagen cross-linkages than LD muscle due to the high pyridinoline (Pyr) content in the endomysium. Finally, a correlation analysis highlighted the multiple correlations between characteristics in different types of collagen during sheep growth. In summary, the collagen characteristics in the IMCT of sheep were impacted by collagen type, muscle type, and age. Furthermore, the various correlations between these characteristics may play an important role in the development of IMCT.

Delivery of bone morphogenetic protein-2 by crosslinking heparin to nile tilapia skin collagen for promotion of rat calvaria bone defect repair.

Collagen has been widely used as a biomaterial for tissue regeneration. At the present, aqua-collagen derived from fish is poorly explored for biomedical material applications due to its insufficient thermal stability. To improve the bone repair ability and thermal stability of fish collagen, the tilapia skin collagen was crosslinked by EDC/NHS with heparin to bind specifically to BMP-2. The thermal stability of tilapia skin collagen crosslinked with heparin (HC-COL) was detected by differential scanning calorimetry (DSC). Cytotoxicity of HC-COL was assessed by detecting MC3T3-E1 cell proliferation using CCK-8 assay. The specific binding of BMP-2 to HC-COL was tested and the bioactivity of BMP-2-loaded HC-COL (HC-COL-BMP-2) was evaluated in vitro by inducing MC3T3-E1 cell differentiation. In vivo, the bone repair ability of HC-COL-2 was evaluated using micro-CT and histological observation. After crosslinking by EDC/NHS, the heparin-linked and the thermostability of the collagen of Nile Tilapia were improved simultaneously. HC-COL has no cytotoxicity. In addition, the binding of BMP-2 to HC-COL was significantly increased. Furthermore, the in vitro study revealed the effective bioactivity of BMP-2 binding on HC-COL by inducing MC3T3-E1 cells with higher ALP activity and the formation of mineralized nodules. In vivo studies showed that more mineralized and mature bone formation was achieved in HC-COL-BMP-2 group. The prepared HC-COL was an effective BMP-2 binding carrier with enough thermal stability and could be a useful biomaterial for bone repair.

Toughness Variations among Natural Casings: An Exploration on Their Biochemical and Histological Characteristics.

We investigated the mechanical, biochemical, and histological properties of hog and sheep casings produced in different countries to elucidate the responsible factors for the toughness quality of natural casings. The toughness and collagen characteristics of sheep and lamb casings were also investigated to elucidate the effect of animal slaughter age on the relationships between connective tissue and the mechanical properties of natural casings. The results showed that the main component of hog and sheep casings was collagen with many layers of sheets. The contents of collagen, elastin, and proteoglycan in hog and sheep casings were similar. The toughest Chinese casings (p < 0.01) possessed a significantly lower heat solubility of collagen (p < 0.01), and a different size and arrangement of collagen fibers. Sheep casings were significantly tougher than lamb casings (p < 0.01). Compared with lamb casings, sheep casings had a significantly low heat-labile collagen content, a low heat solubility of collagen, a large size of collagen fibers, and a high pyridinoline concentration (p < 0.01). Therefore, the high thermal and structural stability of collagen in aged animals may contribute to the enhanced mechanical properties of casings.

The durability of resin-dentine bonds are enhanced by epigallocatechin-3-gallate-encapsulated nanohydroxyapatite/mesoporous silica.

Biomimetic nanohydroxyapatite (nHAp) has long been used as a biocompatible material for bone repair, bone regeneration, and bone reconstruction due to its low toxicity to local or systemic tissues. Various cross-linkers have been employed to maintain the structure of collagen; these include epigallocatechin-3-gallate (EGCG), which can fortify the mechanical properties of collagen and withstand the degradation of collagenase. We hypothesized that EGCG combined with nHAp may promote resin-dentin bonding durability. Here, we examined the effect of epigallocatechin-3-gallate-encapsulated nanohydroxyapatite/mesoporous silica (EGCG@nHAp@MSN) on thermal stability and remineralization capability of dentin collagen. Dentin slices (2 × 2 × 1 mm3 ) were obtained and completely demineralized in a 10% phosphoric acid water solution. The resulting dentin collagen matrix was incubated with deionized water, EGCG, nHAp@MSN, and EGCG@nHAp@MSN. The collagen thermal degradation temperature was assessed utilizing differential scanning calorimetry analysis, which indicated that EGCG, nHAp@MSN, and EGCG@nHAp@MSN reinforced collagen's capability to resist thermal degradation. EGCG@nHAp@MSN resulted in the highest increase in denaturation temperature. Thermogravimetric analysis showed that both nHAp@MSN and EGCG@nHAp@MSN achieved a higher residual mass than the EGCG and control groups. Fourier transform infrared spectroscopy was performed to examine the interaction between EGCG@nHAp@MSN and dentin collagen. The EGCG@nHAp@MSN sample exhibited stronger dentin microhardness and uppermost bond strength after thermocycling. EGCG significantly enhanced collagen's capability to resist thermal degradation. In summary, EGCG and nHAp@MSN may work together to assist the exposed collagen to improve resistance to thermal cycling and promote remineralization while also strengthening the durability of resin-dentin bonds.

606 Identification of first-in-class HSP47 inhibitor and its suppressive role in hypertrophic scars and keloids

Hypertrophic scars (HTS) and keloids are characterized by excessive synthesis and abnormal collagen deposition during wound healing. One of the most important proteins in collagen triple helix formation and stabilization is HSP47, which is highly expressed in pathological scar tissue. Here we report for the first time the discovery of a small molecule HSP47 inhibitor, INV-10000001 (INV-001) which was identified via virtual screening. This was confirmed by the collagen turbidity assay which measures the function of HSP47 and by the surface plasmon resonance assay.

Studies on stabilization of collagen using Cr-doped polydopamine complex

The stabilization of collagen using different small molecules have been explored for the development of biomaterials. One of the most studied molecules in biomaterials research is polydopamine (PDA) due to its ability to bind to different substrates that ranges from metal surface to collagen. Similarly, in leather tanning, chromium has been an extensively used metal ion as it binds strongly with collagen and enhances its stability. However, as per regulatory authority, the presence of chromium in leather has been restricted to minimum level. Here, we studied the application of chromium doped polydopamine (Cr-PDA) complex as collagen stabilizing agent. The preparation and characterization of Cr-PDA were confirmed using FE-SEM, DLS and FT-IR techniques. Cr-PDA did not alter the triple helical structure of collagen as evidenced from the CD spectral data. Cr-PDA delays the fibrillation in collagen compared to collagen or PDA alone. Calorimetric data shows the enhanced stability of collagen when treated with Cr-PDA compared to collagen control but lesser than PDA alone. Viscometry studies have shown that Cr-PDA reduces the viscosity of collagen compared to PDA or collagen alone. Contact angle studies showed that PDA and Cr-PDA imparts more hydrophobicity to collagen compared to control. Tensile strength studies showed that addition of Cr-PDA or PDA increases the tensile strength of the collagen fiber. The present study on stabilization of collagen using Cr-PDA might be helpful in development of crosslinking agents with eco-friendly approach.