Rheological study of in-situ crosslinkable hydrogels based on hyaluronanic acid, collagen and sericin

Albumin-Based Hydrogel Films Covalently Cross-Linked with Oxidized Gellan with Encapsulated Curcumin for Biomedical Applications

Bovine serum albumin (BSA) hydrogels are non-immunogenic, low-cost, biocompatible, and biodegradable. In order to avoid toxic cross-linking agents, gellan was oxidized with NaIO4 to obtain new functional groups like dialdehydes for protein-based hydrogel cross-linking. The formed dialdehyde groups were highlighted with FT-IR and NMR spectroscopy. This paper aims to investigate hydrogel films for biomedical applications obtained by cross-linking BSA with oxidized gellan (OxG) containing immobilized β-cyclodextrin-curcumin inclusion complex (β-CD-Curc) The β-CD-Curc improved the bioavailability and solubility of Curc and was prepared at a molar ratio of 2:1. The film's structure and morphology were evaluated using FT-IR spectroscopy and SEM. The swelling degree (Q%) values of hydrogel films depend on hydrophilicity and pH, with higher values at pH = 7.4. Additionally, the conversion index of -NH2 groups into Schiff bases increases with an increase in OxG amount. The polymeric matrix provides protection for Curc, is non-cytotoxic, and enhances antioxidant activity. At pH = 5.5, the skin permeability and release efficiency of encapsulated curcumin were higher than at pH = 7.4 because of the interaction of free aldehyde and carboxylic groups from hydrogels with amine groups from proteins present in the skin membrane, resulting in a better film adhesion and more efficient curcumin release.

Effect of rheological behaviors of polyacrylonitrile grafted sericin solution on film structure and mechanical properties

Sericin protein possesses excellent biocompatibility, antioxidation, and processability. Nevertheless, manufacturing large quantities of strong and tough pure regenerated sericin materials remains a significant challenge. Herein, we design a lightweight structural sericin film with high ductility by combining radical chain polymerization reaction and liquid-solid phase inversion method. The resulting polyacrylonitrile grafted sericin films exhibit the ability to switch between high strength and high toughness effortlessly, the maximum tensile strength and Young's modulus values are 21.92 ± 1.51 MPa and 8.14 ± 0.09 MPa, respectively, while the elongation at break and toughness reaches up to 344.10 ± 35.40 % and 10.84 ± 1.02 MJ·m-3, respectively. Our findings suggest that incorporating sericin into regenerated films contributes to the transformation of their mechanical properties through influencing the entanglement of molecular chains within polymerized solutions. Structural analyses conducted using infrared spectroscopy and X-ray diffraction confirm that sericin modulates the mechanical properties by affecting the transition of condensed matter conformation. This work presents a convenient yet effective strategy for simultaneously addressing the recycling of sericin as well as producing regenerated protein-based films that hold potential applications in biomedical, wearable, or food packaging.

Preparation and comparison of two medical dressings made from the collagens from fish and bovine

Collagen is used in medical dressings because of its high hydrophilicity, low immunogenicity, excellent biocompatibility, and degradability. These features can promote cell proliferation and platelet agglomeration. Herein, we studied the preparation of gel dressing by using silver carp skin collagen and bovine collagen as raw materials. Their properties and the application effects of collagen gel dressing were evaluated and compared. The centrifugal stability, rheology, and water-loss rate of silver carp skin collagen gel (SCG) and bovine tendon collagen gel (CTG) were determined. Results showed that the two gels were stable, and SCG had better rheology and ductility than CTG. However, the denaturation temperature and water-retention rate of SCG were slightly lower than those of CTG. Two collagen gels were used in the burn-repair experiment of KM mice. Results showed that the SCG and CTG were consistent with the wound-repair effect of commercially available products for shallow II-degree scald and deep II-degree scald. In the superficial shallow II scald experiment, SCG had a faster healing rate in the first 8 days and a shorter recovery time than CTG. In the deep II-degree scald experiment, the wound-healing rate of SCG on the 14th day reached 94.24%, which was 2 days faster than the recovery time of CTG. Moreover, the skin after wound healing was shallower than the scar produced after CTG treatment. Therefore, SCG had the potential to be used as the medical dressing.

Construction of 3D bioprinting of HAP/collagen scaffold in gelation bath for bone tissue engineering

Reconstruction of bone defects remains a clinical challenge, and 3D bioprinting is a fabrication technology to treat it via tissue engineering. Collagen is currently the most popular cell scaffold for tissue engineering; however, a shortage of printability and low mechanical strength limited its application via 3D bioprinting. In the study, aiding with a gelatin support bath, a collagen-based scaffold was fabricated via 3D printing, where hydroxyapatite (HAP) and bone marrow mesenchymal stem cells (BMSCs) were added to mimic the composition of bone. The results showed that the blend of HAP and collagen showed suitable rheological performance for 3D extrusion printing and enhanced the composite scaffold's strength. The gelatin support bath could effectively support the HAP/collagen scaffold's dimension with designed patterns at room temperature. BMSCs in/on the scaffold kept living and proliferating, and there was a high alkaline phosphate expression. The printed collagen-based scaffold with biocompatibility, mechanical properties and bioactivity provides a new way for bone tissue engineering via 3D bioprinting.

3D Printing Type 1 Bovine Collagen Scaffolds for Tissue Engineering Applications-Physicochemical Characterization and In Vitro Evaluation

Collagen, an abundant extracellular matrix protein, has shown hemostatic, chemotactic, and cell adhesive characteristics, making it an attractive choice for the fabrication of tissue engineering scaffolds. The aim of this study was to synthesize a fibrillar colloidal gel from Type 1 bovine collagen, as well as three dimensionally (3D) print scaffolds with engineered pore architectures. 3D-printed scaffolds were also subjected to post-processing through chemical crosslinking (in N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide) and lyophilization. The scaffolds were physicochemically characterized through Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis, Differential Scanning Calorimetry, and mechanical (tensile) testing. In vitro experiments using Presto Blue and Alkaline Phosphatase assays were conducted to assess cellular viability and the scaffolds' ability to promote cellular proliferation and differentiation. Rheological analysis indicated shear thinning capabilities in the collagen gels. Crosslinked and lyophilized 3D-printed scaffolds were thermally stable at 37 °C and did not show signs of denaturation, although crosslinking resulted in poor mechanical strength. PB and ALP assays showed no signs of cytotoxicity as a result of crosslinking. Fibrillar collagen was successfully formulated into a colloidal gel for extrusion through a direct inkjet writing printer. 3D-printed scaffolds promoted cellular attachment and proliferation, making them a promising material for customized, patient-specific tissue regenerative applications.

Biocompatible and Thermoresistant Hydrogels Based on Collagen and Chitosan

Hydrogels are considered good biomaterials for soft tissue regeneration. In this sense, collagen is the most used raw material to develop hydrogels, due to its high biocompatibility. However, its low mechanical resistance, thermal stability and pH instability have generated the need to look for alternatives to its use. In this sense, the combination of collagen with another raw material (i.e., polysaccharides) can improve the final properties of hydrogels. For this reason, the main objective of this work was the development of hydrogels based on collagen and chitosan. The mechanical, thermal and microstructural properties of the hydrogels formed with different ratios of collagen/chitosan (100/0, 75/25, 50/50, 25/75 and 0/100) were evaluated after being processed by two variants of a protocol consisting in two stages: a pH change towards pH 7 and a temperature drop towards 4 °C. The main results showed that depending on the protocol, the physicochemical and microstructural properties of the hybrid hydrogels were similar to the unitary system depending on the stage carried out in first place, obtaining FTIR peaks with similar intensity or a more porous structure when chitosan was first gelled, instead of collagen. As a conclusion, the synergy between collagen and chitosan improved the properties of the hydrogels, showing good thermomechanical properties and cell viability to be used as potential biomaterials for Tissue Engineering.

A Novel Approach of Bioesters Synthesis through Different Technologies by Highlighting the Lowest Energetic Consumption One

Fatty acids esters have a wide application as bioplasticizers and biolubricants in different industries, obtained mainly in classic batch reactors, through an equilibrium complex reaction, that involves high temperatures, long reaction times, vigorously stirring, and much energy consumption. To overcome these shortcomings, we synthesized a series of fatty acid esters (soybean oil fatty acids being the acid components with various hydroxyl compounds) through novel low energy consumption technologies using a bubble column reactor, a microwave field reactor and for comparison meaning, a classic batch reactor. The obtained bioesters physicochemical properties were similar to one another, a good concordance among their rheological properties was obtained, but the energetic consumption is lower when using the bubble column or the microwave reactors instead of the classical batch reactor.

A highly transparent tri-polymer complexin situhydrogel of HA, collagen and four-arm-PEG as potential vitreous substitute

There is a requirement of removal and replacement of vitreous for various ophthalmic diseases, e.g. retinopathy and retinal detachment. Clinical tamponades, e.g. silicone oil and fluorinated gases are used but limited due to their toxicity and some complications. A lot of polymer-based materials have been tested and proposed as vitreous substitute, but till date, there is no ideal vitreous substitute available. Thus, it requires to develop an improved vitreous substitute which will be highly suitable for vitreous replacement. We have developed tri-polymer complexin situhydrogels by crosslinking among hyaluronic acid (HA), collagen (Coll) and four-arm-polyethylene glycol (PEG). All the developed hydrogels are biocompatible with NIH 3T3 mouse fibroblast cells, having pH in the range 7-7.44 and refractive index in the range 1.333-1.345. The developed hydrogels are highly transparent, showing transmittance >97%. FTIR study shows that the hydrogel was crosslinked by amide bond formation between HA and PEG, and between Coll and PEG. The rheological study shows that all the developed hydrogels exhibit viscoelastic behavior and all the hydrogels have storage modulus values (>100 pa) which is greater than loss modulus values-indicating sufficient elasticity for vitreous application. The elastic nature of the hydrogel increases with the increase in PEG concentration. The gel is formed in between 2 and 3 min-indicating its applicationin situ. The viscosity of the developed hydrogels shows shear thinning behavior. The pre-gel solution of the hydrogel is injectable through a 22 G needle-indicating its applicationin situthrough vitrectomy surgery. All the hydrogels are hydrophilic and have water content of 96% approximately. Thus, the results show the positive properties for its application as a potential vitreous substitute.

In-Situ Rheological Studies of Cationic Lignin Polymerization in an Acidic Aqueous System

The chemistry of lignin polymerization was studied in the past. Insights into the rheological behavior of the lignin polymerization system would provide crucial information required for tailoring lignin polymers with desired properties. The in-situ rheological attributes of lignin polymerization with a cationic monomer, [2-(methacryloyloxy)ethyl] trimethylammonium chloride (METAC), were studied in detail in this work. The influences of process conditions, e.g., temperature, component concentrations, and shear rates, on the viscosity variations of the reaction systems during the polymerization were studied in detail. Temperature, METAC/lignin molar ratio, and shear rate increases led to the enhanced viscosity of the reaction medium and lignin polymer with a higher degree of polymerization. The extended reaction time enhanced the viscosity attributing to the larger molecular weight of the lignin polymer. Additionally, the size of particles in the reaction system dropped as reaction time was extended. The lignin polymer with a larger molecular weight and Rg behaved mainly as a viscose (tan δ > 1 or G″ > G') material, while the lignin polymer generated with smaller molecular weight and shorter Rg demonstrated strong elastic characteristics with a tan (δ) lower than unity over the frequency range of 0.1-10 rad/s.

Optimization of the collagen extraction from Nile tilapia skin (Oreochromis niloticus) and its hydrogel with hyaluronic acid

Nile tilapia skin, an abundant waste from fish processing, can be used for collagen extraction, which has a high aggregated value for biomedical applications. Collagen extraction was conducted under different reaction conditions (time, temperature, and concentration of acetic acid) in order to optimize the yield without compromising the integrity of the collagen. Temperature and time were responsible for increased yield. The extraction at 4 and 20 °C produced the acid-solubilized collagen (ASC) with the intact triple helix and was analysed by Fourier-transform infrared spectroscopy (FT-IR) and circular dichroism (CD). The optimized ASC (which used 0.35 mol/L of acetic acid at 20 °C) was consumed to obtain for the first-time fish-based hydrogels with hyaluronic acid (HA) crosslinked with 1-ethyl-3-(3-dimethylaminopropryl carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The hydrogel was characterized by FT-IR, rheology, swelling, and scanning electron microscopy (SEM), confirming that cross-linking was accomplished. It possesses a robust organized network, swells 255 % in PBS and bears interconnected pores with a diameter in the range of 10-100 μm. Until now, col-HA hydrogels crosslinked with EDC/NHS have not been reported in literature with collagen from Nile Tilapia skin. Fish collagen can be a better option than those from land-based animals (cow and pig).

Sericin grafted multifunctional curcumin loaded fluorinated graphene oxide nanomedicines with charge switching properties for effective cancer cell targeting

Fluorinated graphene has recently gained much attention for cancer drug delivery, owing to its peculiar properties including high electronegativity difference, magnetic resonance imaging contrast agent, and the photothermal effect. However, the hydrophobic nature of fluorinated graphene greatly hinders its application as a biological material. Herein, a novel green method is reported for synthesis of a pH-sensitive charge-reversal and water-soluble fluorinated graphene oxide, modified with polyethyleneimine anchored to sericin-polypeptide (FPS). This nanocarrier was further loaded with curcumin (Cur), and characterized as a nanocarrier for anti-cancer drug delivery. The synthesized nanocarriers contain two different pH-sensitive amide linkages, which are negatively charged in blood pH (≈7.4) and can prolong circulation times. The amide linkages undergo hydrolysis once they reach the mildly acidic condition (pH≈6.5, corresponding to tumor extracellular matrix), and subsequently once reached the lower acidic condition (pH≈5.5, corresponded to endo/lysosomes microenvironment), the FPS charge can be switched to positive (≈+28 mV), which aids the nuclear release. This nanocarrier was designed to selectively enhance cell internalization and nuclear-targeted delivery of curcumin in HeLa, SkBr3 and PC-3 cancer cells. Moreover, FPS-Cur demonstrated high curcumin loading capacity, prolonged curcumin release and promotion of apoptosis in HeLa, SkBr3 and PC-3 cells. Therefore, with its pH-responsive charge-reversal properties, FPS-Cur would be a promising candidate for chemotherapy of cervical, breast and prostate cancers.

Hydrogels: soft matters in photomedicine

Photodynamic therapy (PDT), a shining beacon in the realm of photomedicine, is a non-invasive technique that utilizes dye-based photosensitizers (PSs) in conjunction with light and oxygen to produce reactive oxygen species to combat malignant tissues and infectious microorganisms. Yet, for PDT to become a common, routine therapy, it is still necessary to overcome limitations such as photosensitizer solubility, long-term side effects (e.g., photosensitivity) and to develop safe, biocompatible and target-specific formulations. Polymer based drug delivery platforms are an effective strategy for the delivery of PSs for PDT applications. Among them, hydrogels and 3D polymer scaffolds with the ability to swell in aqueous media have been deeply investigated. Particularly, hydrogel-based formulations present real potential to fulfill all requirements of an ideal PDT platform by overcoming the solubility issues, while improving the selectivity and targeting drawbacks of the PSs alone. In this perspective, we summarize the use of hydrogels as carrier systems of PSs to enhance the effectiveness of PDT against infections and cancer. Their potential in environmental and biomedical applications, such as tissue engineering photoremediation and photochemistry, is also discussed.

Flow Behavior Prior to Crosslinking: The Need for Precursor Rheology for Placement of Hydrogels in Medical Applications and for 3D Bioprinting

Hydrogels - water swollen cross-linked networks - have demonstrated considerable promise in tissue engineering and regenerative medicine applications. However, ambiguity over which rheological properties are needed to characterize these gels before crosslinking still exists. Most hydrogel research focuses on the performance of the hydrogel construct after implantation, but for clinical practice, and for related applications such as bioinks for 3D bioprinting, the behavior of the pre-gelled state is also critical. Therefore, the goal of this review is to emphasize the need for better rheological characterization of hydrogel precursor formulations, and standardized testing for surgical placement or 3D bioprinting. In particular, we consider engineering paste or putty precursor solutions (i.e., suspensions with a yield stress), and distinguish between these differences to ease the path to clinical translation. The connection between rheology and surgical application as well as how the use of paste and putty nomenclature can help to qualitatively identify material properties are explained. Quantitative rheological properties for defining materials as either pastes or putties are proposed to enable easier adoption to current methods. Specifically, the three-parameter Herschel-Bulkley model is proposed as a suitable model to correlate experimental data and provide a basis for meaningful comparison between different materials. This model combines a yield stress, the critical parameter distinguishing solutions from pastes (100-2000 Pa) and from putties (>2000 Pa), with power law fluid behavior once the yield stress is exceeded. Overall, successful implementation of paste or putty handling properties to the hydrogel precursor may minimize the surgeon-technology learning time and ultimately ease incorporation into current practice. Furthermore, improved understanding and reporting of rheological properties will lead to better theoretical explanations of how materials affect rheological performances, to better predict and design the next generation of biomaterials.

Tuning of elasticity and surface properties of hydrogel cell culture substrates by simple chemical approach

When designing materials for tissue engineering applications various parameters characterizing both materials and tissue have to be taken into account. The characteristics such as chemistry, elasticity, wettability, roughness and morphology of the substrate's surface have significant impact on cell behavior. The paper presents biopolymer (collagen/chitosan) based hydrogel materials with tunable elasticity and surface properties useful for fabrication of substrates for cell culture. Using simple chemical approach involving the change in concentration of crosslinking agent (genipin) and composition of the reaction mixture the hydrogels characterized with various features were obtained. Detailed analysis of morphology, topography, roughness and elasticity of surface performed using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and rheological measurements has shown that the topographical aspects and roughness parameter can be modulated in nanoscale regime (13-47 nm). Substrate's elasticity could be modified in a wide range (0.2-270 kPa). Biological in vitro studies on fibroblasts behavior revealed that the materials prepared provide satisfactory conditions for cell culture, ensuring their high viability, good adhesion and normal morphology. The genipin crosslinked collagen-chitosan hydrogels characterized by denser fiber structure, higher elasticity and lower surface roughness are the most attractive supports for fibroblasts cultivation. The results obtained indicate that the properties of the materials developed can be easily tailored to the needs of the given type of cells.

Non-immunogenic, porous and antibacterial chitosan and Antheraea mylitta silk sericin hydrogels as potential dermal substitute

Limitation of existing grafts including restricted donor site, risks of immune reactions, infectious diseases and high cost alarms the growing need of natural, cost effective and functional graft as the dermal substitute. We fabricate stable (>6 weeks) and porous (57.23-75.22μm) yet flexible (in variable pH) matrices using Antheraea mylitta sericin crosslinked with well known biocompatible polysaccharide chitosan by natural crosslinker (genipin) without using any harsh chemical. The fabricated matrices are characterized in terms of chemical modifications (Fourier transform infrared spectroscopy), crystallinity (X-ray diffraction), swelling, degradability and thermal stability. The hydrogels show good adhesion, migration, proliferation and viability of human dermal fibroblasts. The matrices cause no significant immune response of inflammatory cytokines (TNF-α and IL-1β) and hemolysis of human blood. These also retain their intrinsic antioxidant (196.1±17.7μM Fe (II)/mg) and antibacterial (8-15mm zone of inhibition) properties. These results indicate their potential as a cost effective and antibacterial dermal substitute.

Osteogenesis evaluation of duck's feet-derived collagen/hydroxyapatite sponges immersed in dexamethasone

Background

The aim of this study was to investigate the osteogenesis effects of DC and DC/HAp sponge immersed in without and with dexamethasone.

Methods

The experimental groups in this study were DC and DC/HAp sponge immersed in without dexamethasone (Dex(−)DC and Dex(−)-DC/HAp group) and with dexamethasone (Dex(+)-DC and Dex(+)-DC/HAp group). We characterized DC and DC/HAp sponge using compressive strength, scanning electron microscopy (SEM). Also, osteogenic differentiation of BMSCs on sponge (Dex(−)DC, Dex(−)-DC/HAp, Dex(+)-DC and Dex(+)-DC/HAp group) was assessed by SEM, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazoliumbromide (MTT) assay, alkaline phosphatase (ALP) activity assay and reverse transcription-PCR (RT-PCR).

Results

In this study, we assessed osteogenic differentiation of BMSCs on Duck’s feet-derived collagen (DC)/HAp sponge immersed with dexamethasone Dex(+)-DC/HAp. These results showed that Dex(+)-DC/HAp group increased cell proliferation and osteogenic differentiation of BMSCs during 28 days.

Conclusion

From these results, Dex(+)-DC/HAp can be envisioned as a potential biomaterial for bone regeneration applications.

Self-Crosslinking of Silk Fibroin Using H2O2-Horseradish Peroxidase System and the Characteristics of the Resulting Fibroin Membranes

Silk fibroin has been widely used in biomedical and clinical fields owing to its good biocompatibility. In the present work, self-crosslinking of fibroin molecules was carried out using the hydrogen peroxide (H₂O₂)-horseradish peroxidase system, followed by preparation of the fibroin membranes, aiming at improving the mechanical property of fibroin-based material and expanding its applications. P-Hydroxyphenylacetamide (PHAD), as the model compound of tyrosine residues in fibroins, was used to investigate the possibility of horseradish peroxidase (HRP)-catalyzed crosslinking. The results were characterized by means of 1H NMR and UPLC-TQD. The efficacy of enzymatic crosslinking of silk fibroins was examined by determining the changes in the relative viscosity, amino acid compositions, and SEC chromatogram. The obtained data indicated that H₂O₂-HRP incubation led to PHAD polymerization, and the molecular weight of fibroin proteins was also noticeably increased after the enzymatic treatment. CD and ATR-FTIR spectra revealed that H₂O₂-HRP treatments had an evident impact on the conformational structure of silk fibroins. The mechanical property and thermal behavior for the modified fibroin membrane were noticeably improved compared to the untreated. Meanwhile, the obtained membrane exhibited good biocompatibility according to the cell growth experiment. The present work provides a novel method for preparation of the fibroin-based materials for biomedical applications.