Analysis of the Physico-Chemical, Mechanical and Biological Properties of Crosslinked Type-I Collagen from Horse Tendon: Towards the Development of Ideal Scaffolding Material for Urethral Regeneration

On the effect of pepsin incubation on type I collagen from horse tendon: Fine tuning of its physico-chemical and rheological properties

Type I collagen is commonly recognized as the gold standard biomaterial for the manufacturing of medical devices for health-care related applications. In recent years, with the final aim of developing scaffolds with optimal bioactivity, even more studies focused on the influence of processing parameters on collagen properties, since processing can strongly affect the architecture of collagen at various length scales and, consequently, scaffolds macroscopic performances. The ability to finely tune scaffold properties in order to closely mimic the tissues' hierarchical features, preserving collagen's natural conformation, is actually of great interest. In this work, the effect of the pepsin-based extraction step on the material final properties was investigated. Thus, the physico-chemical properties of fibrillar type I collagens upon being extracted under various conditions were analyzed in depth. Correlations of collagen structure at the supramolecular scale with its microstructural properties were done, confirming the possibility of tuning rheological, viscoelastic and degradation properties of fibrillar type I collagen.

Travelling through the Natural Hierarchies of Type I Collagen with X-rays: From Tendons of Cattle, Horses, Sheep and Pigs

Type I collagen physiological scaffold for tissue regeneration is considered one of the widely used biomaterials for tissue engineering and medical applications. It is hierarchically organized: five laterally staggered molecules are packed within fibrils, arranged into fascicles and bundles. The structural organization is correlated to the direction and intensity of the forces which can be loaded onto the tissue. For a tissue-specific regeneration, the required macro- and microstructure of a suitable biomaterial has been largely investigated. Conversely, the function of multiscale structural integrity has been much less explored but is crucial for scaffold design and application. In this work, collagen was extracted from different animal sources with protocols that alter its structure. Collagen of tendon shreds excised from cattle, horse, sheep and pig was structurally investigated by wide- and small-angle X-ray scattering techniques, at both molecular and supramolecular scales, and thermo-mechanically with thermal and load-bearing tests. Tendons were selected because of their resistance to chemical degradation and mechanical stresses. The multiscale structural integrity of tendons' collagen was studied in relation to the animal source, anatomic location and source for collagen extraction.

Decellularization of the human urethra for tissue engineering applications

Recently, several scaffolds have been introduced for urethral tissue engineering. However, acellular human urethral scaffold harvested from deceased donors may provide significant advantages compared to synthetic, composite, or other biological scaffolds. This study aims to develop the protocol for decellularization of the human urethra that preserves substantial extracellular matrix (ECM) components, which are essential for subsequent recellularization mimicking the natural environment of the native ECM. A total of 12 human urethras were harvested from deceased donors. An equal part of every harvested urethra was used as a control sample for analyses. The protocol design was based on the enzyme-detergent-enzyme method. Trypsin and Triton X-100 were used to remove cells, followed by DNase treatment to remove DNA residues. Subsequently, the specimens were continually rinsed in deionized water for seven days. The efficiency of decellularization was determined by histochemistry, immunohistochemical staining, scanning electron microscopy (SEM), and DNA quantification. Histological analysis confirmed cell removal and preservation of urethral structure after decellularization. The preservation of collagen IV and fibronectin was confirmed by histologic examination and immunohistochemical staining. SEM confirmed the maintenance of the ultrastructural architecture of ECM and fibers. DNA content in decellularized urethra was significantly lower compared to the native sample (P < 0.001), and so the criteria for decellularized tissue were met. Cytotoxicity analysis data showed that the matrix-conditioned medium did not contain soluble toxins and had no significant inhibitory effect on cell proliferation, providing evidence that the decellularized samples are not toxic. This study demonstrates the feasibility of the enzyme-detergent-enzyme-based decellularization protocol for removing cellular components and maintaining urethral ECM and its ultrastructure. Moreover, obtained results provide solid ground for recellularization and urethral tissue engineering, which will follow.

Collagen Membrane as Water-Based Gel Electrolyte for Electrochromic Devices

Bio-based polymers are attracting great interest due to their potential for several applications in place of conventional polymers. In the field of electrochemical devices, the electrolyte is a fundamental element that determines their performance, and polymers represent good candidates for developing solid-state and gel-based electrolytes toward the development of full-solid-state devices. In this context, the fabrication and characterization of uncrosslinked and physically cross-linked collagen membranes are reported to test their potential as a polymeric matrix for the development of a gel electrolyte. The evaluation of the membrane's stability in water and aqueous electrolyte and the mechanical characterization demonstrated that cross-linked samples showed a good compromise in terms of water absorption capability and resistance. The optical characteristics and the ionic conductivity of the cross-linked membrane, after overnight dipping in sulfuric acid solution, demonstrated the potential of the reported membrane as an electrolyte for electrochromic devices. As proof of concept, an electrochromic device was fabricated by sandwiching the membrane (after sulfuric acid dipping) between a glass/ITO/PEDOT:PSS substrate and a glass/ITO/SnO₂ substrate. The results in terms of optical modulation and kinetic performance of such a device demonstrated that the reported cross-linked collagen membrane could represent a valid candidate as a water-based gel and bio-based electrolyte for full-solid-state electrochromic devices.

An Update on the Clinical Efficacy and Safety of Collagen Injectables for Aesthetic and Regenerative Medicine Applications

Soft tissues diseases significantly affect patients quality of life and usually require targeted, costly and sometimes constant interventions. With the average lifetime increase, a proportional increase of age-related soft tissues diseases has been witnessed. Due to this, the last two decades have seen a tremendous demand for minimally invasive one-step resolutive procedures. Intensive scientific and industrial research has led to the recognition of injectable formulations as a new advantageous approach in the management of complex diseases that are challenging to treat with conventional strategies. Among them, collagen-based products are revealed to be one of the most promising among bioactive biomaterials-based formulations. Collagen is the most abundant structural protein of vertebrate connective tissues and, because of its structural and non-structural role, is one of the most widely used multifunctional biomaterials in the health-related sectors, including medical care and cosmetics. Indeed, collagen-based formulations are historically considered as the "gold standard" and from 1981 have been paving the way for the development of a new generation of fillers. A huge number of collagen-based injectable products have been approved worldwide for clinical use and have routinely been introduced in many clinical settings for both aesthetic and regenerative surgery. In this context, this review article aims to be an update on the clinical outcomes of approved collagen-based injectables for both aesthetic and regenerative medicine of the last 20 years with an in-depth focus on their safety and effectiveness for the treatment of diseases of the integumental, gastrointestinal, musculoskeletal, and urogenital apparatus.

Development of L-Lysine-Loaded PLGA Microparticles as a Controlled Release System for Angiogenesis Enhancement

Vascularization is a highly conserved and considerably complex and precise process that is finely driven by endogenous regulatory processes at the tissue and systemic levels. However, it can reveal itself to be slow and inadequate for tissue repair and regeneration consequent to severe lesions/damages. Several biomaterial-based strategies were developed to support and enhance vasculogenesis by supplying pro-angiogenic agents. Several approaches were adopted to develop effective drug delivery systems for the controlled release of a huge variety of compounds. In this work, a microparticulate system was chosen to be loaded with the essential amino acid L-lysine, a molecule that has recently gained interest due to its involvement in pro-angiogenic, pro-regenerative, and anti-inflammatory mechanisms. Poly (lactic-co-glycolic acid), the most widely used FDA-approved biodegradable synthetic polymer for the development of drug delivery systems, was chosen due to its versatility and ability to promote neovascularization and wound healing. This study dealt with the development and the effectiveness evaluation of a PLGA-based microparticulate system for the controlled release of L-lysine. Therefore, in order to maximize L-lysine encapsulation efficiency and tune its release kinetics, the microparticle synthesis protocol was optimized by varying some processing parameters. All developed formulations were characterized from a morphological and physicochemical point of view. The optimized formulation was further characterized via the evaluation of its preliminary biological efficacy in vitro. The cellular and molecular studies revealed that the L-lysine-loaded PLGA microparticles were non-toxic, biocompatible, and supported cell proliferation and angiogenesis well by stimulating the expression of pro-angiogenic genes such as metalloproteinase-9, focal adhesion kinases, and different growth factors. Thus, this work showed the potential of delivering L-lysine encapsulated in PLGA microparticles as a cost-effective promoter system for angiogenesis enhancement and rapid healing.

Age-Related Properties of Aquaponics-Derived Tilapia Skin (Oreochromis niloticus): A Structural and Compositional Study

In the last two decades, fisheries and fish industries by-products have started to be recovered for the extraction of type I collagen because of issues related to the extraction of traditional mammalian tissues. In this work, special attention has been paid to by-products from fish bred in aquaponic plants. The valorization of aquaponic fish wastes as sources of biopolymers would make the derived materials eco-friendlier and attractive in terms of profitability and cost effectiveness. Among fish species, Nile Tilapia is the second-most farmed species in the world and its skin is commonly chosen as a collagen extraction source. However, to the best of our knowledge, no studies have been carried out to investigate, in depth, the age-related differences in fish skin with the final aim of selecting the most advantageous fish size for collagen extraction. In this work, the impact of age on the structural and compositional properties of Tilapia skin was evaluated with the aim of selecting the condition that best lends itself to the extraction of type I collagen for biomedical applications, based on the known fact that the properties of the original tissue have a significant impact on those of the final product. Performed analysis showed statistically significant age-related differences. In particular, an increase in skin thickness (+110 µm) and of wavy-like collagen fiber bundle diameter (+3 µm) besides their organization variation was observed with age. Additionally, a preferred collagen molecule orientation along two specific directions was revealed, with a higher fiber orientation degree according to age. Thermal analysis registered a shift of the endothermic peak (+1.7 °C) and an increase in the enthalpy (+3.3 J/g), while mechanical properties were found to be anisotropic, with an age-dependent brittle behavior. Water (+13%) and ash (+0.6%) contents were found to be directly proportional with age, as opposed to protein (-8%) and lipid (-10%) contents. The amino acid composition revealed a decrease in the valine, leucine, isoleucine, and threonine content and an increase in proline and hydroxyproline. Lastly, fatty acids C14:0, C15:0, C16:1, C18:2n6c, C18:3n6, C18:0, C20:3n3, and C23:0 were revealed to be upregulated, while C18:1n9c was downregulated with age.

WAXS and SAXS Investigation of Collagen-Rich Diet Effect on Multiscale Arrangement of Type I Collagen in Tilapia Skin Fed in Aquaponics Plant

Type I collagen is the main component of the extracellular matrix that acts as the physical and biochemical support of tissues. Thanks to its characteristics, collagen is widely employed as a biomaterial for implantable device fabrication and as antiaging food supplementation. Because of the BSE transmission in the 1990s, aquatic animals have become a more suitable extraction source than warm-blooded animals. Moreover, as recently demonstrated, a supplementing diet with fish collagen can increase the body’s collagen biosynthesis. In this context, Tilapia feeding was supplemented with hydrolyzed collagen in order to enhance the yield of extracted collagen. Tilapia skin was investigated with wide and small angle scattering techniques, analyzing the collagen structure from the submolecular to the nanoscale and correlated with Differential Scanning Calorimetry (DSC) measurements. Our studies demonstrated that the supplementation appears to have an effect at the nanoscale in which fibrils appear more randomly oriented than in fish fed with no supplemented feed. Conversely, no effect of a collagen-rich diet was observed at the submolecular scale.

Aquaponics-Derived Tilapia Skin Collagen for Biomaterials Development

Collagen is one of the most widely used biomaterials in health-related sectors. The industrial production of collagen mostly relies on its extraction from mammals, but several issues limited its use. In the last two decades, marine organisms attracted interest as safe, abundant, and alternative source for collagen extraction. In particular, the possibility to valorize the huge quantity of fish industry waste and byproducts as collagen source reinforced perception of fish collagen as eco-friendlier and particularly attractive in terms of profitability and cost-effectiveness. Especially fish byproducts from eco-sustainable aquaponics production allow for fish biomass with additional added value and controlled properties over time. Among fish species, Oreochromis niloticus is one of the most widely bred fish in large-scale aquaculture and aquaponics systems. In this work, type I collagen was extracted from aquaponics-raised Tilapia skin and characterized from a chemical, physical, mechanical, and biological point of view in comparison with a commercially available analog. Performed analysis confirmed that the proprietary process optimized for type I collagen extraction allowed to isolate pure native collagen and to preserve its native conformational structure. Preliminary cellular studies performed with mouse fibroblasts indicated its optimal biocompatibility. All data confirmed the eligibility of the extracted Tilapia-derived native type I collagen as a biomaterial for healthcare applications.

Investigations on the Influence of Collagen Type on Physicochemical Properties of PVP/PVA Composites Enriched with Hydroxyapatite Developed for Biomedical Applications

Nowadays, a great attention is directed into development of innovative multifunctional composites which may support bone tissue regeneration. This may be achieved by combining collagen and hydroxyapatite showing bioactivity, osteoconductivity and osteoinductivity with such biocompatible polymers as polyvinylpyrrolidone (PVP) and poly(vinyl alcohol) (PVA). Here PVA/PVP-based composites modified with hydroxyapatite (HAp, 10 wt.%) and collagen (30 wt.%) were obtained via UV radiation while two types of collagen were used (fish and bovine) and crosslinking agents differing in the average molecular weight. Next, their chemical structure was characterized using Fourier transform infrared (FT-IR) spectroscopy, roughness of their surfaces was determined using a stylus contact profilometer while their wettability was evaluated by a sessile drop method followed by the measurements of their surface free energy. Subsequently, swelling properties of composites were verified in simulated physiological liquids as well as the behavior of composites in these liquids by pH measurements. It was proved that collagen-modified composites showed higher swelling ability (even 25% more) compared to unmodified ones, surface roughness, biocompatibility towards simulated physiological liquids and hydrophilicity (contact angles lower than 90°). Considering physicochemical properties of developed materials and a possibility of the preparation of their various shapes and sizes, it may be concluded that developed materials showed great application potential for biomedical use, e.g., as materials filling bone defects supporting their treatments and promoting bone tissue regeneration due to the presence of hydroxyapatite with osteoinductive and osteoconductive properties.