Assessment of the Influence of Acetic Acid Residue on Type I Collagen during Isolation and Characterization

Self-sensing magnetic actuator based on sustainable collagen hybrid nanocomposites

Taking into account that natural polymers are renewable and biodegradable, hybrid materials based on natural polymers are required for advanced technological applications with reduced environmental footprint. In this work, sustainable composites have been developed based on collagen as a polymeric matrix and different magnetic fillers, in order to tailor magnetic response. The composites were prepared by solution casting with 30 wt% of magnetite nanoparticles (Fe3O4 NPs), magnetite nanorods (Fe3O4 NRs) or cobalt ferrite nanoparticles (CoFe2O4 NPs). It is shown that the magnetic filler type has no bearing on the morphology, physical-chemical, or thermal characteristics of the composites, whereas the mechanical properties are determined by the magnetic filler, leading to a reduction in tensile strength, with values of 4.95 MPa for Fe3O4 NPs, 9.20 MPa for Fe3O4 NRs and 5.21 MPa for CoFe2O4 NPs containing samples. However, the highest magnetization saturation is obtained for Fe3O4 NPs (44 emu.g-1) and the higher coercive field for CoFe2O4 NPs (2062 Oe). In order to prove functionality of the developed composites, a self-sensing magnetic actuator device has been developed with the composite film with CoFe2O4 NPs, showing high stability over cycling.

A parathyroid hormone related supramolecular peptide for multi-functionalized osteoregeneration

Supramolecular peptide nanofiber hydrogels are emerging biomaterials for tissue engineering, but it is difficult to fabricate multi-functional systems by simply mixing several short-motif-modified supramolecular peptides because relatively abundant motifs generally hinder nanofiber cross-linking or the formation of long nanofiber. Coupling bioactive factors to the assembling backbone is an ideal strategy to design multi-functional supramolecular peptides in spite of challenging synthesis and purification. Herein, a multi-functional supramolecular peptide, P1R16, is developed by coupling a bioactive factor, parathyroid hormone related peptide 1 (PTHrP-1), to the basic supramolecular peptide RADA16-Ⅰ via solid-phase synthesis. It is found that P1R16 self-assembles into long nanofibers and co-assembles with RADA16-Ⅰ to form nanofiber hydrogels, thus coupling PTHrP-1 to hydrogel matrix. P1R16 nanofiber retains osteoinductive activity in a dose-dependent manner, and P1R16/RADA16-Ⅰ nanofiber hydrogels promote osteogenesis, angiogenesis and osteoclastogenesis in vitro and induce multi-functionalized osteoregeneration by intramembranous ossification and bone remodeling in vivo when loaded to collagen (Col) scaffolds. Abundant red blood marrow formation, ideal osteointegration and adapted degradation are observed in the 50% P1R16/Col scaffold group. Therefore, this study provides a promising strategy to develop multi-functional supramolecular peptides and a new method to topically administrate parathyroid hormone or parathyroid hormone related peptides for non-healing bone defects.

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.

Sustainable Collagen Blends with Different Ionic Liquids for Resistive Touch Sensing Applications

Considering the sustainable development goals to reduce environmental impact, sustainable sensors based on natural polymers are a priority as the large im plementation of these materials is required considering the Internet of Things (IoT) paradigm. In this context, the present work reports on sustainable blends based on collagen and different ionic liquids (ILs), including ([Ch][DHP], [Ch][TSI], [Ch][Seri]) and ([Emim][TFSI]), processed with varying contents and types of ILs in order to tailor the electrical response. Varying IL types and contents leads to different interactions with the collagen polymer matrix and, therefore, to varying mechanical, thermal, and electrical properties. Collagen/[Ch][Seri] samples display the most pronounced decrease of the tensile strength (3.2 ± 0.4 MPa) and an increase of the elongation at break (50.6 ± 1.5%). The best ionic conductivity value of 0.023 mS cm^-1 has been obtained for the sample with 40 wt % of the IL [Ch][Seri]. The functional response of the collagen-IL films has been demonstrated on a resistive touch sensor whose response depends on the ionic conductivity, being suitable for the next generation of sustainable touch sensing devices.

A novel peptide isolated from Catla skin collagen acts as a self-assembling scaffold promoting nucleation of calcium-deficient hydroxyapatite nanocrystals

Catla collagen hydrolysate (CH) was fractionated by chromatography and each fraction was subjected to HA nucleation, with the resultant HA-fraction composites being scored based on the structural and functional group of the HA formed. The process was repeated till a single peptide with augmented HA nucleation capacity was obtained. The peptide (4.6 kDa), exhibited high solubility, existed in polyproline-II conformation and displayed a dynamic yet stable hierarchical self-assembling property. The 3D modelling of the peptide revealed multiple calcium and phosphate binding sites and a high propensity to self-assemble. Structural analysis of the peptide-HA crystals revealed characteristic diffraction planes of HA with mineralization following the (002) plane, retention of the self-assembled hierarchy of the peptide and intense ionic interactions between carboxyl groups and calcium. The peptide-HA composite crystals were mostly of 25-40 nm dimensions and displayed 79% mineralization, 92% crystallinity, 39.25% porosity, 12GPa Young's modulus and enhanced stability in physiological pH. Cells grown on peptide-HA depicted faster proliferation rates and higher levels of osteogenic markers. It was concluded that the prerequisite for HA nucleation by a peptide included: a conserved sequence with a unique charge topology allowing calcium chelation and its ability to form a dynamic self-assembled hierarchy for crystal propagation.

Marine origin biomaterials using a compressive and absorption methodology as cell-laden hydrogel envisaging cartilage tissue engineering

In the recent decade, marine origin products have been growingly studied as building blocks complying with the constant demand of the biomedical sector regarding the development of new devices for Tissue Engineering and Regenerative Medicine (TERM). In this work, several combinations of marine collagen-chitosan-fucoidan hydrogel were formed using a newly developed eco-friendly compressive and absorption methodology to produce hydrogels (CAMPH), which consists of compacting the biopolymers solution while removing the excess of water. The hydrogel formulations were prepared by blending solutions of 5% collagen from jellyfish and/or 3% collagen from blue shark skin, with solutions of 3% chitosan from squid pens and solutions of 10% fucoidan from brown algae, at different ratios. The biopolymer physico-chemical characterization comprised Amino Acid analysis, ATR-FTIR, CD, SDS-PAGE, ICP, XRD, and the results suggested the shark/jellyfish collagen(s) conserved the triple helical structure and had similarities with type I and type II collagen, respectively. The studied collagens also contain a denaturation temperature of around 30-32 °C and a molecular weight between 120 and 125 kDa. Additionally, the hydrogel properties were determined by rheology, water uptake ability, degradation rate, and SEM, and the results showed that all formulations had interesting mechanical (strong viscoelastic character) and structural stability properties, with a significant positive highlight in the formulation of H₃ (blending all biopolymers, i.e., 5% collagen from jellyfish, 3% collagen from skin shark, 3% chitosan and 10% of fucoidan) in the degradation test, that shows a mass loss around 18% over the 30 days, while the H₁ and H₂, present a mass loss of around 35% and 44%, respectively. Additionally, the in vitro cellular assessments using chondrocyte cells (ATDC5) in encapsulated state revealed, for all hydrogel formulations, a non-cytotoxic behavior. Furthermore, Live/Dead assay and Phalloidin/DAPI staining, to assess the cytoskeletal organization, proved that the hydrogels can provide a suitable microenvironment for cell adhesion, viability, and proliferation, after being encapsulated. Overall, the results show that all marine collagen (jellyfish/shark)-chitosan-fucoidan hydrogel formulations provide a good structural architecture and microenvironment, highlighting the H₃ biomaterial due to containing more polymers in their composition, making it suitable for biomedical articular cartilage therapies.

Limbal Bio-engineered Tissue Employing 3D Nanofiber-Aerogel Scaffold to Facilitate LSCs Growth and Migration

Constrained by the existing scaffold inability to mimic limbal niche, limbal bio-engineered tissue constructed in vitro is challenging to be widely used in clinical practice. Here, 3D nanofiber-aerogel scaffold was fabricated by employing thermal cross-linking electrospinned film Polycaprolactone (PCL) and gelatin (GEL) as the precursor. Benefiting from the cross-linked (160°C, vacuum) structure, the homogenized and lyophilized 3D nanofiber-aerogel scaffold with preferable mechanical strength was capable of refraining the volume collapse in humid vitro. Intriguingly, compared with traditional electrospinning scaffolds, our 3D nanofiber-aerogel scaffolds possessed enhanced water absorption (1100%-1300%), controllable aperture (50-100 μm) and excellent biocompatibility (optical density value, 0.953 ± 0.021). The well-matched aperture and nanostructure of the scaffolds with cells enabled the construction of limbal bio-engineered tissue. It is foreseen that the proposed general method could be extended to various aerogels, providing new opportunities for the development of novel limbal bio-engineered tissue. This article is protected by copyright. All rights reserved.

Development of New Collagen/Clay Composite Biomaterials

The fabrication of collagen-based biomaterials for skin regeneration offers various challenges for tissue engineers. The purpose of this study was to obtain a novel series of composite biomaterials based on collagen and several types of clays. In order to investigate the influence of clay type on drug release behavior, the obtained collagen-based composite materials were further loaded with gentamicin. Physiochemical and biological analyses were performed to analyze the obtained nanocomposite materials after nanoclay embedding. Infrared spectra confirmed the inclusion of clay in the collagen polymeric matrix without any denaturation of triple helical conformation. All the composite samples revealed a slight change in the 2-theta values pointing toward a homogenous distribution of clay layers inside the collagen matrix with the obtaining of mainly intercalated collagen-clay structures, according X-ray diffraction analyses. The porosity of collagen/clay composite biomaterials varied depending on clay nanoparticles sort. Thermo-mechanical analyses indicated enhanced thermal and mechanical features for collagen composites as compared with neat type II collagen matrix. Biodegradation findings were supported by swelling studies, which indicated a more crosslinked structure due additional H bonding brought on by nanoclays. The biology tests demonstrated the influence of clay type on cellular viability but also on the antimicrobial behavior of composite scaffolds. All nanocomposite samples presented a delayed gentamicin release when compared with the collagen-gentamicin sample. The obtained results highlighted the importance of clay type selection as this affects the performances of the collagen-based composites as promising biomaterials for future applications in the biomedical field.

Preparation and Characterization of Thermally Stable Collagens from the Scales of Lizardfish (Synodus macrops)

Marine collagen is gaining vast interest because of its high biocompatibility and lack of religious and social restrictions compared with collagen from terrestrial sources. In this study, lizardfish (Synodus macrops) scales were used to isolate acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC). Both ASC and PSC were identified as type I collagen with intact triple-helix structures by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and spectroscopy. The ASC and PSC had high amino acids of 237 residues/1000 residues and 236 residues/1000 residues, respectively. Thus, the maximum transition temperature (T_max) of ASC (43.2 °C) was higher than that of PSC (42.5 °C). Interestingly, the T_max of both ASC and PSC was higher than that of rat tail collagen (39.4 °C) and calf skin collagen (35.0 °C), the terrestrial collagen. Solubility tests showed that both ASC and PSC exhibited high solubility in the acidic pH ranges. ASC was less susceptible to the “salting out” effect compared with PSC. Both collagen types were nontoxic to HaCaT and MC3T3-E1 cells, and ASC was associated with a higher cell viability than PSC. These results indicated that ASC from lizardfish scales could be an alternative to terrestrial sources of collagen, with potential for biomedical applications.

Mimicking the Hierarchical Organization of Natural Collagen: Toward the Development of Ideal Scaffolding Material for Tissue Regeneration

Biological materials found in living organisms, many of which are proteins, feature a complex hierarchical organization. Type I collagen, a fibrous structural protein ubiquitous in the mammalian body, provides a striking example of such a hierarchical material, with peculiar architectural features ranging from the amino acid sequence at the nanoscale (primary structure) up to the assembly of fibrils (quaternary structure) and fibers, with lengths of the order of microns. Collagen plays a dominant role in maintaining the biological and structural integrity of various tissues and organs, such as bone, skin, tendons, blood vessels, and cartilage. Thus, "artificial" collagen-based fibrous assemblies, endowed with appropriate structural properties, represent ideal substrates for the development of devices for tissue engineering applications. In recent years, with the ultimate goal of developing three-dimensional scaffolds with optimal bioactivity able to promote both regeneration and functional recovery of a damaged tissue, numerous studies focused on the capability to finely modulate the scaffold architecture at the microscale and the nanoscale in order to closely mimic the hierarchical features of the extracellular matrix and, in particular, the natural patterning of collagen. All of these studies clearly show that the accurate characterization of the collagen structure at the submolecular and supramolecular levels is pivotal to the understanding of the relationships between the nanostructural/microstructural properties of the fabricated scaffold and its macroscopic performance. Several studies also demonstrate that the selected processing, including any crosslinking and/or sterilization treatments, can strongly affect the architecture of collagen at various length scales. The aim of this review is to highlight the most recent findings on the development of collagen-based scaffolds with optimized properties for tissue engineering. The optimization of the scaffolds is particularly related to the modulation of the collagen architecture, which, in turn, impacts on the achieved bioactivity.

Preparation and Evaluation of Collagen-Based Patches as Curcumin Carriers

Patients with psoriasis are dissatisfied with the standard pharmacological treatments, whether systemic or topical, with many of them showing interest in complementary and alternative medicine. Curcumin (Cur), a natural polyphenol derived from turmeric, has recently gained attention for skin-related diseases because of its proven anti-inflammatory action. However, topical treatment with Cur would be inadequate because of its hydrophobicity, instability, and low bioavailability. In addition, hyperkeratosis and lack of moisture in psoriatic skin result in low penetration that would prevent actives from permeating the stratum corneum. In this work, a polymer-based formulation of Cur for the topical treatment of psoriasis is reported. To improve the physicochemical stability of Cur, it was first encapsulated in chitosan nanoparticles. The Cur-loaded nanoparticles were incorporated in a hydrophilic, biocompatible collagen-based patch. The nanoparticle-containing porous collagen patches were then chemically cross-linked. Morphology, chemical interactions, swelling ratio, enzymatic hydrolysis, and Cur release from the patches were evaluated. All patches showed excellent swelling ratio, up to ~1500%, and after cross-linking, the pore size decreased, and their hydrolysis rates decelerated. The in vitro release of Cur was sustained with an initial burst release, reaching 55% after 24 h. Cur within the scaffolds imparted a proliferation inhibitory effect on psoriatic human keratinocytes in vitro.