Bifunctional Hybrid Composites from Collagen Biowastes for Heterogeneous Applications

Biodegradable and biocompatible collagen-based hybrid materials for force sensing applications

With the aim of replacing synthetic macromolecules by biological macromolecules for advanced applications, collagen films were produced with two different ionic liquids (ILs), choline dihydrogen phosphate ([Ch][DHP]) and choline serinate ([Ch][Seri]), added in order to modulate the electrical responses. The films were prepared by casting, varying IL content between 0 and 6 wt%. The morphology and thermal properties of the resulting films were found to be independent of both IL type and content. However, the highest direct curret (d.c.) electrical conductivity (1.4 × 10-8 S·cm-1) was achieved for collagen films containing 3 wt% [Ch][DHP]. Furthermore, it was demonstrated that IL/collagen films were non-cytotoxic, with cell activity values exceeding 70 %. These collagen films were proven to be suitable for force sensing applications, displaying excellent sensitivity and stability upon repeated testing.

Collagen Biocomposites Derived from Fish Waste: Doped and Cross-Linked with Functionalized Fe3O4 Nanoparticles and Their Comparative Studies with a Green Approach

Collagen-based nanobiocomposites can reabsorb and are biodegradable. These properties are effectively controlled by the number of cross-links. This study demonstrates an effortless and proficient approach for the functionalization of Fe₃O₄ NPs for cross-linking collagen obtained from biowaste, viz., fish scales of Lates Calcarifer, a marine origin. The size of Fe₃O₄ NPs (10-40 nm) was confirmed using particle size analysis. The physico-chemical properties of the aminosilane-coated Fe₃O₄ NPs cross-linked via succinylated collagen (FFCSC) were characterized using different analytical techniques and compared with succinylated collagen doped with Fe₃O₄ NPs (FDSC). Thermogravimetric analysis indicates cross-linked product FFCSC to be more stable than the FDSC. Also, the antibacterial effect was more pronounced for FFCSC than for FDSC nanobiocomposites. FFCSC exhibited improved mechanical properties which are essential for materials used for wound dressing purposes. Moreover, the cell viability of fibroblasts (3T3-L1) and their morphology studied by SEM and fluorescence microscopy showed biocompatibility of both FDSC and FFCSC. Thus, the current investigation, involves a waste to wealth approach where the collagen-based nanobiocomposites present an easy way to recycle the biowaste to value-added products using simple and clean methods, which are suitable for use in biomedical and environmental applications.

Collagen processing with mesoscale aggregates as templates and building blocks

Collagen presents a well-organized hierarchical multilevel structure. Microfibers, fibers, and fiber bundles are the aggregates of natural collagen; which achieve an ideal balance of mechanical strength and toughness at the mesoscopic scale for biological tissue. These mesostructured aggregates of collagen isolated from biological tissues retain these inherent organizational features to enable their use as building blocks for constructing new collagen materials with ideal mechanical performance, thermal and dimensional stability. This strategy is distinct from the more common bottom-up or molecular-level design and assembly approach to generating collagen materials. The present review introduces the hierarchical structure of biological collagen with a focus on mesostructural features. Isolation strategies for these collagen aggregates (CAs) are summarized. Recent progress in the use of these mesostructural components for the construction of new collagen materials with emerging applications is reviewed, including in catalysis, environmental applications, biomedicine, food packaging, electrical energy storage, and flexible sensors. Finally, challenges and prospects are assessed for controllable production of CAs as well as material designs.

Discovery of protein-based natural hydrogel from the girdle of the 'sea cockroach' Chiton articulatus (Chitonida: Chitonidae)

Hydrogels are widely used materials in biomedical, pharmaceutical, cosmetic, and agricultural fields. However, these hydrogels are usually formed synthetically via a long and complicated process involving crosslinking natural polymers. Herein, we describe a natural hydrogel isolated using a 'gentle' acid treatment from the girdle of a chiton species (Chiton articulatus). This novel hydrogel is shown to have a proliferative effect on mouse fibroblast cells (cell line, L929). The swelling capacity of this natural hydrogel was recorded as approximately 1,200% in distilled water, which is within desired levels for hydrogels. Detailed characterizations reveal that the hydrogel consists predominantly (83.93%) of protein. Considering its non-toxicity, proliferative effect and swelling properties, this natural hydrogel is an important discovery for material sciences, with potential for further applications in industry. Whether the girdle has some hydrogel activity in the living animal is unknown, but we speculate that it may enable the animal to better survive extreme environmental conditions by preventing desiccation.

Characterization of Composite Nano-Bioscaffolds Based on Collagen and Supercritical Fluids-Assisted Decellularized Fibrous Extracellular Matrix

Nano-bioscaffolds obtained from decellularized tissues have been employed in several medical applications. Nano-bioscaffolds could provide structural support for cell attachment and a suitable environment with sufficient porosity for cell growth and proliferation. In this study, a new combined method constitutes a decellularization protocol to remove the tissue and cellular molecules from porcine dermis for preparation of nano-bioscaffolds with fibrous extracellular matrix via pre- and post-treatment of supercritical fluids. The supercritical fluids-assisted nano-bioscaffolds were characterized by peptide identification, infrared spectrum of absorption, morphology, histological observations, DNA quantification, and hemocompatibility. Further, the resulting nano-bioscaffolds could be employed to obtain new cross-linked composite nano-bioscaffold containing collagen and acellular matrix.

Conductive Skeleton-Heterostructure Composites Based on Chrome Shavings for Enhanced Electromagnetic Interference Shielding

Renewable bio-based electromagnetic interference (EMI) shielding materials receive increasing attention undoubtedly. However, there is still a challenge to use raw biomass materials to construct a significant structure through an effortless and environmental route for EMI shielding applications. Herein, for the first time, we demonstrated a hybrid composite of multi-walled carbon nanotube/polypyrrole/chrome-tanned collagen fiber (MWCNT/PPy/CF), which utilized waste chrome shavings as a matrix. X-ray photoelectron spectroscopy reveals that the chromium on the CF has a binding effect on the PPy layer, which endows the tight integration between the CF and PPy layer. After the MWCNT network was loaded on the PPy layer, this ternary structure could provide stable conductive paths and a rich number of polarized interfaces. The MWCNT/PPy/CF composite exhibits superior electrical conductivity (354 ± 52 S/m), higher than PPy/CF (222 ± 38 S/m) and MWCNT/CF (104 ± 11 S/m), owing to the synergy of dual conductive structures. Notably, the shielding effectiveness (SE) value of the MWCNT/PPy/CF composite reaches 30 dB in the X band at a thickness of 0.48 mm. The shielding effectiveness of reflection (SE_R) (9.1 dB) is similar to that of PPy/CF (8.2 dB), while the shielding effectiveness of absorption (SE_A) is significantly improved from 15.3 dB (PPy/CF) to 20.4 dB (MWCNT/PPy/CF) due to the additional coverage of the MWCNT network. This indicates the synergy between the MWCNT network and conductive PPy/CF skeleton. This work provided a method to prepare sustainable and low-cost renewable EMI shielding materials using chrome shavings. Meanwhile, this novel structure combining a conductive skeleton and heterostructure can be considered as a potential application in relevant fields.

Characterization of organophosphatic brachiopod shells: spectroscopic assessment of collagen matrix and biomineral components

The shells of linguloid brachiopods such as Lingula and Discinisca are inorganic-organic nanocomposites with a mineral phase of calcium phosphate (Ca-phosphate). Collagen, the main extracellular matrix in Ca-phosphatic vertebrate skeletons, has not previously been clearly resolved at the molecular level in organophosphatic brachiopods. Here, modern and recently-alive linguliform brachiopod shells of Lingula and Discinisca have been studied by microRaman spectroscopy, Fourier transform infrared spectroscopy, field emission gun scanning electron microscopy, and thermal gravimetric analysis. For the first time, biomineralized collagen matrix and Ca-phosphate components were simultaneously identified, showing that the collagen matrix is an important moiety in organophosphatic brachiopod shells, in addition to prevalent chitin. Stabilized nanosized apatitic biominerals (up to ∼50 nm) permeate the framework of organic fibrils. There is a ∼2.5-fold higher wt% of carbonate (CO₃ ^2-) in Lingula versus Discinisca shells. Both microRaman spectroscopy and infrared spectra show transient amorphous Ca-phosphate and octacalcium phosphate components. For the first time, trivalent moieties at ∼1660 cm^-1 and divalent moieties at ∼1690 cm^-1 in the amide I spectral region were identified. These are related to collagen cross-links that are abundant in mineralized tissues, and could be important features in the biostructural and mechanical properties of Ca-phosphate shell biominerals. This work provides a critical new understanding of organophosphatic brachiopod shells, which are some of the earliest examples of biomineralization in still-living animals that appeared in the Cambrian radiation.