Comparison of the Impact of NaIO4-Accelerated, Cu2+/H2O2-Accelerated, and Novel Ion-Accelerated Methods of Poly(l-DOPA) Coating on Collagen-Sealed Vascular Prostheses: Strengths and Weaknesses

Sensitive biomaterials subjected to surface modification require delicate methods to preserve their structures and key properties. These include collagen-sealed polyester vascular prostheses. For their functionalization, coating with polycatecholamines (PCAs) can be used. PCAs change some important biological properties of biomaterials, e.g., hydrophilicity, bioactivity, antibacterial activity, and drug binding. The coating process can be stimulated by oxidants, organic solvents, or process conditions. However, these factors may change the properties of the PCA layer and the matrix itself. In this work, collagen-sealed vascular grafts were functionalized with a poly(l-DOPA) (PLD) layer using novel seawater-inspired ion combination as an accelerator, compared to the sodium periodate, Cu2+/H2O2 mixture, and accelerator-free reference methods. Then, poly(l-DOPA) was used as the interface for antibiotic binding. The coated prostheses were characterized (SEM, FIB-SEM, FTIR, UV/vis), and their important functional parameters (mechanical, antioxidant, hemolytic, and prothrombotic properties, bioactivity, stability in human blood and simulated body fluid (SBF), antibiotic binding, release, and antibacterial activity) were compared. It was found that although sodium periodate increased the strength and drug-binding capacity of the prosthesis, it also increased the blood hemolysis risk. Cu2+/H2O2 destabilized the mechanical properties of the coating and the graft. The seawater-inspired ion-accelerated method was efficient, stable, and matrix- and human blood-friendly, and it stimulated hydroxyapatite formation on the prosthesis surface. The results lead to the conclusion that selection of the PCA formation accelerator should be based on a careful analysis of the biological properties of medical devices. They also suggest that the ion-accelerated method of PLD coating on medical devices may be highly effective and safer than the oxidant-accelerated coating method.

Innovative Approach to Accelerate Wound Healing: Synthesis and Validation of Enzymatically Cross-Linked COL-rGO Biocomposite Hydrogels

In this study, an innovative conductive hybrid biomaterial was synthetized using collagen (COL) and reduced graphene oxide (rGO) in order for it to be used as a wound dressing. The hydrogels were plasticized with glycerol and enzymatically cross-linked with horseradish peroxidase (HRP). A successful interaction among the components was demonstrated by FTIR, XRD, and XPS. It was demonstrated that increasing the rGO concentration led to higher conductivity and negative charge density values. Moreover, rGO also improved the stability of hydrogels, which was expressed by a reduction in the biodegradation rate. Furthermore, the hydrogel's stability against the enzymatic action of collagenase type I was also strengthened by both the enzymatic cross-linking and the polymerization of dopamine. However, their absorption capacity, reaching values of 215 g/g, indicates the high potential of the hydrogels to absorb fluids. The rise of these properties positively influenced the wound closure process, achieving an 84.5% in vitro closure rate after 48 h. These findings clearly demonstrate that these original composite biomaterials can be a viable choice for wound healing purposes.

Janus structure hydrogels: recent advances in synthetic strategies, biomedical microstructure and (bio)applications

Janus structure hydrogels (JSHs) are novel materials. Their primary fabrication methods and various applications have been widely reported. JSHs are primarily composed of Janus particles (JNPs) and polysaccharide components. They exhibit two distinct physical or chemical properties, generating intriguing characteristics due to their asymmetric structure. Normally, one side (adhesive interface) is predominantly constituted of polysaccharide components, primarily serving excellent adhesion. On the other side (functional surface), they integrate diverse functionalities, concurrently performing a plethora of synergistic functions. In the biomedical field, JSHs are widely applied in anti-adhesion, drug delivery, wound healing, and other areas. It also exhibits functions in seawater desalination and motion sensing. Thus, JSHs hold broad prospects for applications, and they possess significant research value in nanotechnology, environmental science, healthcare, and other fields. Additionally, this article proposes the challenges and future work facing these fields.

Modulation of macrophage polarization by secondary cross-linked hyaluronan-dopamine hydrogels

The inflammatory response plays a critical role in standard tissue repair processes, wherein active modulation of macrophage polarization is necessary for wound healing. Dopamine, a mussel-inspired bioactive material, is widely involved in wound healing, neural/bone/myocardial regeneration, and more. Recent studies indicated that dopamine-modified biomaterials can potentially alter macrophages polarization towards a pro-healing phenotype, thereby enhancing tissue regeneration. Nevertheless the immunoregulatory activity of dopamine on macrophage polarization remains unclear. This study introduces a novel interpenetrating hydrogel to bridge this research gap. The hydrogel, combining varying concentrations of oxidized dopamine with hyaluronic acid hydrogel, allows precise regulation of mechanical properties, antioxidant bioactivity, and biocompatibility. Surprisingly, both in vivo and in vitro outcomes demonstrated that dopamine concentration modulates macrophage polarization, but not linearly. Lower concentration (2 mg/mL) potentially decrease inflammation and facilitate M2 type macrophage polarization. In contrast, higher concentration (10 mg/mL) exhibited a pro-inflammatory tendency in the late stages of implantation. RNA-seq analysis revealed that lower dopamine concentrations induced the M1/M2 transition of macrophages by modulating the NF-κB signaling pathway. Collectively, this research offers valuable insights into the immunoregulation effects of dopamine-integrated biomaterials in tissue repair and regeneration.

Robust adhesive nanocomposite sponge composed of citric acid and nano clays modified cellulose for rapid hemostasis of lethal non-compressible hemorrhage

Massive bleeding control plays the main role in saving people's lives in emergency situations. Herein, modified cellulose-based nanocomposite sponges by polydopamine (PDA) and laponite nano-clay was developed to sturdily deal with non-compressible lethal severe bleeding. PDA accomplishes supreme adhesion in the bleeding site (∼405 kPa) to form strong physical barrier and seal the position. Sponges super porous (∼70 % porosity) and super absorbent capacity (48 g blood absorbed per 1 g sponge) by concentrating the blood cells and platelets provides the requirements for primary hemostasis. Synergistically, the nanocomposite sponges' intelligent chemical structure induces hemostasis by activation of the XI, IX, X, II and FVII factors of intrinsic and extrinsic coagulation pathways. Excellent hemostatic performance of sponges in-vitro was assessed by RBC accumulation (∼100 %), blood clotting index (∼10 %), platelet aggregation/activation (∼93 %) and clotting time. The nanocomposite sponges depicted super performance in the fatal high-pressure non-compressible hemorrhage model by reducing of >2, 15 and 3 times in the bleeding amount at New Zealand rabbit's heart and liver, and rat's femoral artery bleeding models, respectively compared to commercial hemostatic agents (Pvalue˂0.001). The in-vivo host response results exhibited biosafety with no systemic and significant local inflammatory response by hematological, pathological and biochemical parameters assessments.

An Investigation into the Stability Source of Collagen Fiber Modified Using Cr(III): An Adsorption Isotherm Study

The enhanced hydrothermal stability of leather, imparted by little Cr(III), has traditionally been ascribed to strong coordinate bonds. However, this explanation falls short when considering that the heat-induced shrinking of collagen fiber is predominantly driven by rupturing weak H-bonds. This study explored the stability source via adsorption thermodynamics using collagen fiber as an adsorbent. Eleven isotherm models were fitted with the equilibrium dataset. Nine of these models aptly described Cr(III) adsorption based on the physical interpretations of model parameters and error functions. The adsorption equilibrium constants from six models could be transformed into dimensionless thermodynamic equilibrium constants. Based on the higher R2 of the van't Hoff equation, thermodynamic parameters (∆G°, ∆H°, ∆S°) from the Fritz-Shluender isotherm model revealed that the adsorption process typifies endothermic and spontaneous chemisorption, emphasizing entropy increase as the primary driver of Cr(III) bonding with collagen. Thus, the release of bound H2O from collagen is identified as the stability source of collagen fiber modified by Cr(III). This research not only clarifies the selection and applicability of the isotherm model in a specific aqueous system but also identifies entropy, rather than enthalpy, as the principal stability source of Cr-leather. These insights facilitate the development of novel methods to obtain stable collagen-based material.

Effects of Phenolics on the Physicochemical and Structural Properties of Collagen Hydrogel

In the current era, the treatment of collagen hydrogels with natural phenolics for the improvement in physicochemical properties has been the subject of considerable attention. The present research aimed to fabricate collagen hydrogels cross-linked with gallic acid (GA) and ellagic acid (EA) at different concentrations depending on the collagen dry weight. The structural, enzymatic, thermal, morphological, and physical properties of the native collagen hydrogels were compared with those of the GA/EA cross-linked hydrogels. XRD and FTIR spectroscopic analyses confirmed the structural stability and reliability of the collagen after treatment with either GA or EA. The cross-linking also significantly contributed to the improvement in the storage modulus, of 435 Pa for 100% GA cross-linked hydrogels. The thermal stability was improved, as the highest residual weight of 43.8% was obtained for the hydrogels cross-linked with 50% GA in comparison with all the other hydrogels. The hydrogels immersed in 30%, 50%, and 100% concentrations of GA also showed improved swelling behavior and porosity, and the highest resistance to type 1 collagenase (76.56%), was obtained for 50% GA cross-linked collagen hydrogels. Moreover, GA 100% and EA 100% obtained the highest denaturation temperatures (Td) of 74.96 °C and 75.78 °C, respectively. In addition, SEM analysis was also carried out to check the surface morphology of the pristine collagen hydrogels and the cross-linked collagen hydrogels. The result showed that the hydrogels cross-linked with GA/EA were denser and more compact. However, the improved physicochemical properties were probably due to the formation of hydrogen bonds between the phenolic hydroxyl groups of GA and EA and the nitrogen atoms of the collagen backbone. The presence of inter- and intramolecular cross-links between collagen and GA or EA components and an increased density of intermolecular bonds suggest potential hydrogen bonding or hydrophobic interactions. Overall, the present study paves the way for further investigations in the field by providing valuable insights into the GA/EA interaction with collagen molecules.

Synthesis, Characterization, and Induced Osteogenic Differentiation Effect of Collagen Membranes Functionalized by Polydopamine/Graphene Oxide for Bone Tissue Engineering

Collagen is one of the most common natural absorbable polymers, which is widely used as a barrier membrane in biomedical fields due to its many desirable biological properties. However, absorbable membranes such as collagen have their own disadvantages such as unpredictable degradation rates, poor rigidity leading to tissue collapse, and limited osteogenic properties and cell adhesion. In this study, a modified collagen membrane with a polydopamine-graphene oxide (PDA/GO) complex was synthesized to improve the characteristics of collagen for bone tissue engineering. The successful synthesis of PDA/GO on collagen membranes was verified using X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The wettability of PDA/GO-modified collagen membranes was considerably improved based on the characterization by water contact angle compared to the uncoated membranes and surface coatings solely by either PDA or GO. The modified PDA/GO coating also enhanced the mechanical properties such as tensile strength and biodegradation rate of collagen membranes. In addition, the PDA/GO coating effectively enhanced the biocompatibility of collagen membranes as verified by the enhanced proliferation and adhesion of human bone marrow stem cells (hBMSCs). Additionally, the effects of PDA/GO coating on the osteogenic differentiation of hBMSCs on collagen membranes were investigated through alkaline phosphatase (ALP) activity and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The PDA/GO coating on collagen membranes resulted in a significant increase in osteogenic properties compared with the uncoated collagen membranes. According to the results of the current study, the combination of PDA and GO-modified collagen membranes could be used for bone tissue engineering and biomedical applications.

Distribution, Typical Structure and Self-Assembly Properties of Collagen from Fish Skin and Bone

The source and type of collagen are crucial to its application, and both play a decisive role. Collagen was prepared from both tilapia skin and bone and skate skin and cartilage, named as CI-TI-s, CI-TI-b, CI-SK-s, and CII-SK-c, respectively. Types, distributions, structures, and self-assembly of collagen were studied. It showed that yellow collagen fibers from skin arranged longitudinally, while collagen fibers from skate cartilages displayed varying colors. CI-TI-s, CI-TI-b, CI-SK-s, and CII-SK-c showed the typical amide A (3316-3336 cm-1) and amide B (2929-2948 cm-1) in FTIR spectra. CI-TI-b and CII-SK-c showed 218-229 nm of UV absorption, 11.56-12.20 Å of d values in XRD, and 0.12-0.14 of Rpn values in CD. The thermal denaturation temperatures of CI-TI-s and CI-SK-s were 30.7 and 20.6 °C, respectively. The self-assembly of CI-TI-s and CII-SK-c were maximum at pH 7.2 and 7.4-7.6, respectively. The unique collagen peptides of tilapia and skate were GPSGPQGAVGATGPK, PAMPVPGPMGPMGPR, SPAMPVPGPMGPMGPR, GESGPSGPAGPAGPAGVR, SSGPPVPGPIGPMGPR, GLTGPIGVPGPPGAQGEK, GLAGPQGPR, and GLSGDPGVQGIK, respectively. The unique peptides of type I and type II collagen were GPTGEIGATGLAGAR, GVLGLTGMR, LGLTGMR, GEPGAAGPAGPSGPMGPR, SSGPPVPGPIGPMGPR, and GLSGDPGVQGIK, respectively.

Functional Enhancement of Guar Gum−Based Hydrogel by Polydopamine and Nanocellulose

The development of green, biomedical hydrogels using natural polymers is of great significance. From this viewpoint, guar gum (GG) has been widely used for hydrogel preparation; however, its mechanical strength and adhesion often cannot satisfy the biomedical application. Therefore, in the present study, gelatin and a cellulose nanocrystal (CNC) were first applied to overcome the defects of guar gum hydrogel. Dopamine was self−polymerized into polydopamine (PDA) on the gelatin chain at alkaline condition, and gelatin−polydopamine (Gel−PDA) further cross−linked with guar gum and CNC via the borate−didiol bond, intramolecular Schiff base reaction, and Michael addition. CNC not only interacted with guar gum using borate chemistry but also acted as a mechanical reinforcer. The obtained Gel−PDA+GG+CNC hydrogel had an excellent self−healing capacity, injectability, and adhesion due to the catechol groups of PDA. Moreover, dopamine introduction caused a significant increase in the anti−oxidant activity. This hydrogel was cyto− and hemo−compatible, which implies a potential usage in the medical field.

Accelular nanofibrous bilayer scaffold intrapenetrated with polydopamine network and implemented into a full-thickness wound of a white-pig model affects inflammation and healing process

Treatment of complete loss of skin thickness requires expensive cellular materials and limited skin grafts used as temporary coverage. This paper presents an acellular bilayer scaffold modified with polydopamine (PDA), which is designed to mimic a missing dermis and a basement membrane (BM). The alternate dermis is made from freeze-dried collagen and chitosan (Coll/Chit) or collagen and a calcium salt of oxidized cellulose (Coll/CaOC). Alternate BM is made from electrospun gelatin (Gel), polycaprolactone (PCL), and CaOC. Morphological and mechanical analyzes have shown that PDA significantly improved the elasticity and strength of collagen microfibrils, which favorably affected swelling capacity and porosity. PDA significantly supported and maintained metabolic activity, proliferation, and viability of the murine fibroblast cell lines. The in vivo experiment carried out in a domestic Large white pig model resulted in the expression of pro-inflammatory cytokines in the first 1-2 weeks, giving the idea that PDA and/or CaOC trigger the early stages of inflammation. Otherwise, in later stages, PDA caused a reduction in inflammation with the expression of the anti-inflammatory molecule IL10 and the transforming growth factor β (TGFβ1), which could support the formation of fibroblasts. Similarities in treatment with native porcine skin suggested that the bilayer can be used as an implant for full-thickness skin wounds and thus eliminate the use of skin grafts.

A highly stretchable, UV resistant and underwater adhesive hydrogel based on xylan derivative for sensing

Hydrogels with fascinating adhesion have been demonstrated great potential in various applications. However, most hydrogels lose their adhesion in wet or underwater environments due to the influence of interfacial water. Inspired by mussel, an underwater adhesive hydrogel was facilely fabricated by introducing electrostatic interactions, which consisted of poly (acrylic acid) (PAA), quaternized xylan (QAX) and tannic acid (TA). In this hydrogel, -COO^- from PAA, -N⁺(CH₃)₃ from QAX and catechol group from TA resembled amino acids with negative and positive charges and 3,4-dihydroxyphenylalanine units in mussel, which endowed the hydrogels with great underwater adhesion through multiple interactions. Notably, acrylic acid (AA) played a key role in the dispersion of the system. QAX, a biomass derived from plants with excellent properties, worked with PAA to construct hydrogel networks. The resultant hydrogels exhibited excellent mechanical properties including remarkable stretchability (>4000 %) and compressibility. Moreover, the hydrogels had superior UV-blocking (~99.96 %), and showed good adhesion both in air and underwater. The hydrogels can be exploited as a wearable sensor to monitor human motions and even subtle motions, which have the potential to be explored in human health monitoring.

Novel Trends in Hydrogel Development for Biomedical Applications: A Review

Nowadays, there are still numerous challenges for well-known biomedical applications, such as tissue engineering (TE), wound healing and controlled drug delivery, which must be faced and solved. Hydrogels have been proposed as excellent candidates for these applications, as they have promising properties for the mentioned applications, including biocompatibility, biodegradability, great absorption capacity and tunable mechanical properties. However, depending on the material or the manufacturing method, the resulting hydrogel may not be up to the specific task for which it is designed, thus there are different approaches proposed to enhance hydrogel performance for the requirements of the application in question. The main purpose of this review article was to summarize the most recent trends of hydrogel technology, going through the most used polymeric materials and the most popular hydrogel synthesis methods in recent years, including different strategies of enhancing hydrogels’ properties, such as cross-linking and the manufacture of composite hydrogels. In addition, the secondary objective of this review was to briefly discuss other novel applications of hydrogels that have been proposed in the past few years which have drawn a lot of attention.

An injectable and biodegradable hydrogel incorporated with photoregulated NO generators to heal MRSA-infected wounds

The development of degradable hydrogel fillers with high antibacterial activity and wound-healing property is urgently needed for the treatment of infected wounds. Herein, an injectable, degradable, photoactivated antibacterial hydrogel (MPDA-BNN6@Gel) was developed by incorporating BNN6-loaded mesoporous polydopamine nanoparticles (MPDA-BNN6 NPs) into a fibrin-based hydrogel. After administration, MPDA-BNN6@Gel created local hyperthermia and released large quantities of NO gas to treat methicillin-resistant Staphylococcus aureus infection under the stimulation of an 808 nm laser. Experiments confirmed that the bacteria were eradicated through irreversible damage to the cell membrane, genetic metabolism, and material energy. Furthermore, in the absence of laser irradition, the fibrin and small amount of NO that originated from MPDA-BNN6@Gel promoted wound healing in vivo. This work indicates that MPDA-BNN6@Gel is a promising alternative for the treatment of infected wounds and provides a facile tactic to design a photoregulated bactericidal hydrogel for accelerating infected wound healing. STATEMENT OF SIGNIFICANCE: The development of a degradable hydrogel with high antibacterial activity and wound-healing property is an urgent need for the treatment of infected wounds. Herein, an injectable, degradable, and photo-activated antibacterial hydrogel (MPDA-BNN6@Gel) has been developed by incorporating BNN6-loaded mesoporous polydopamine nanoparticles (MPDA-BNN6 NPs) into a fibrin-based hydrogel. After administration of MPDA-BNN6@Gel, the MPDA-BNN6@Gel could generate local hyperthermia and release large quantities of NO gas to treat the methicillin-resistant Staphylococcus aureus infection under the irradiation of 808 nm laser. Furthermore, in the absence of a laser, the fibrin and a small amount of NO originating from MPDA-BNN6@Gel could promote wound healing in vivo.

Osteogenic and angiogenic bioactive collagen entrapped calcium/zinc phosphates coating on biodegradable Zn for orthopedic implant applications

Zinc is becoming one of the leading candidate materials for biodegradable orthopedic implants owing to its attractive properties in terms of degradation behavior and mechanical properties. However, the insufficient surface bio-activities postpone its clinical application. In this study, an organic-inorganic collagen entrapped calcium/zinc phosphates coating was constructed on Zn surface to lessen Zn²⁺ releasing rate and to leverage the surface osteogenic and angiogenic properties. Collagen molecules were immobilized onto Zn substrate and subsequently coordinated with calcium and zinc ions to promote the CaZnP inorganic phase growth, ensuing an intertwined collagen-CaZnP hybrid system. Consequently, the hybrid coating was highly coalesced and compact. Such high quality warranted the contained Zn²⁺ releasing in a tolerable rate favorable for cells viability. The collagen-CaZnP coated Zn showed remarkedly stronger osteogenicity as compared to the untreated Zn, ascertained by the MC3T3-E1 osteoblast cell proliferation and differentiation assays, such as alkaline phosphatase expression and calcium nodule formation results. In addition, this hybrid coating supported human umbilical vein endothelial cells (HUVECs) migration and tube formation. The enhanced osteogenic and angiogenic properties could be ascribed to the nature of collagen and calcium/zinc phosphate components, the hybrid micro/nano-structure as well as the ability of controlling the Zn²⁺ release of Zn substrate into a suitable concentration range. Our strategy provides a new avenue to surface modification of biodegradable metals for bone regenerative perspective.

Adhesive and biodegradable membranes made of sustainable catechol-functionalized marine collagen and chitosan

We describe bioadhesive membranes developed from marine renewable biomaterials, namely chitosan and collagen extracted from fish skins. Collagen was functionalized with catechol groups (Coll-Cat) to provide the membranes with superior adhesive properties in a wet environment and blended with chitosan to improve the mechanical properties. The blended membranes were compared to chitosan and chitosan blended with unmodified collagen in terms of surface morphology, wettability, weight loss, water uptake, mechanical and adhesive properties. The metabolic activity, the viability and the morphology of L929 fibroblastic cells seeded on these membranes were also assessed. Our results show that the functionalization with catechol groups improves the adhesive and mechanical properties of the membranes and enhances cell attachment and proliferation. These data suggest that the developed marine origin-raw membranes present a potential towards the restoration of the structural and functional properties of damaged soft tissues.

Development of a multifunctional injectable temperature-sensitive gelatin-based adhesive double-network hydrogel

Gelatin-based bioadhesives are suitable for the treatment of wounds due to their inherent biocompatibility, lack of immunogenicity, and potential for modification. However, common limitations with such adhesives include their adhesive strength and versatility. In the present study, a multifunctional injectable temperature-sensitive gelatin-based adhesive double-network hydrogel (DNGel) was engineered using facile dual-syringe methodology. An integrative crosslinking strategy utilized the complexation of catechol-Fe³⁺ and NIPAAm-methacryloyl. As anticipated, the DNGel exhibited multifunctional therapeutic properties, namely temperature-sensitivity, mechanical flexibility, good adhesive strength, injectability, self-healing capability, antibacterial activity, and the capability to enable hemostasis and wound healing. The bioinspired dynamic double-network was stabilized by a number of molecular interactions between components in the DNGel, providing multifunctional therapeutic performance. In addition, comprehensive in vitro and in vivo testing confirmed that the adhesive hydrogel exhibited effective antihemorrhagic properties and accelerated wound healing by the promotion of revascularization, representing considerable potential as a next-generation multifunctional smart adhesive patch.

c-Axis-Oriented Platelets of Crystalline Hydroxyapatite in Biomimetic Intrafibrillar Mineralization of Polydopamine-Functionalized Collagen Type I

Mineralized collagen fibrils are important basic building blocks of calcified tissues, such as bone and dentin. Polydopamine (PDA) can introduce functional groups, i.e., hydroxyl and amine groups, on the surfaces of type I collagen (Col-I) as possible nucleation sites of calcium phosphate (CaP) crystallization. Molecular bindings in between PDA and Col-I fibrils (Col-PDA) have been found to significantly reduce the interfacial energy. The wetting effect, mainly hydrophilicity due to the functional groups, escalates the degree of mineralization. The assembly of Col-I molecules into fibrils was initiated at the designated number of collagenous molecules and PDA. In contrast to the infiltration of amorphous calcium phosphate (ACP) precursors into the Col-I matrix by polyaspartic acid (pAsp), this collagen assembly process allows nucleation and ACP to exist in advance by PDA in the intrafibrillar matrix. PDA bound to specific sites, i.e., gap and overlap zones, by the regular arrangement of Col-I fibrils enhanced ACP nucleation and thus mineralization. As a result, the c-axis-oriented platelets of crystalline hydroxyapatite in the Col-I fibril matrix were observed in the enhanced mineralization through PDA functionalization.

A novel hydrogel with self-healing property and bactericidal activity

In this study, we have designed and synthesized a novel poly (4 - vinyl benzene boronic acid - co - N - vinyl pyrrolidone - co - 1 - vinyl - 3 - butylimidazolium bromide) hydrogel (VNV hydrogel) dressing with good self-healing properties and bactericidal activity. The gelation and self-healing of this hydrogel are mainly achieved by the formation of a dynamic B-O-B bond between the polymer chains, which is fractured by external forces and subsequently reformed. This self-healing mechanism is studied in detail through the molecular design of the hydrogel. The introduction of hydrophilic chemical groups can effectively improve the porous structures, water absorption and molecular migration. These properties have a positive effect on improving self-healing properties of dynamic crosslinked hydrogels. Furthermore, this VNV hydrogel dressing displays good antibacterial activity against E. coli, S. aureus, and C. albicans. The application of VNV hydrogel dressing on rat wound surface can effectively accelerate wound healing. These results indicate that this novel VNV hydrogel dressing with good self-healing properties and bactericidal activity has potential applications in wound dressings.

Upgrading of marine (fish and crustaceans) biowaste for high added-value molecules and bio(nano)-materials

Currently, the Earth is subjected to environmental pressure of unprecedented proportions in the history of mankind. The inexorable growth of the global population and the establishment of large urban areas with increasingly higher expectations regarding the quality of life are issues demanding radically new strategies aimed to change the current model, which is still mostly based on linear economy approaches and fossil resources towards innovative standards, where both energy and daily use products and materials should be of renewable origin and 'made to be made again'. These concepts have inspired the circular economy vision, which redefines growth through the continuous valorisation of waste generated by any production or activity in a virtuous cycle. This not only has a positive impact on the environment, but builds long-term resilience, generating business, new technologies, livelihoods and jobs. In this scenario, among the discards of anthropogenic activities, biodegradable waste represents one of the largest and highly heterogeneous portions, which includes garden and park waste, food processing and kitchen waste from households, restaurants, caterers and retail premises, and food plants, domestic and sewage waste, manure, food waste, and residues from forestry, agriculture and fisheries. Thus, this review specifically aims to survey the processes and technologies for the recovery of fish waste and its sustainable conversion to high added-value molecules and bio(nano)materials.

Polydopamine and collagen coated micro-grated polydimethylsiloxane for human mesenchymal stem cell culture

Natural tissues contain highly organized cellular architecture. One of the major challenges in tissue engineering is to develop engineered tissue constructs that promote cellular growth in physiological directionality. To address this issue, micro-patterned polydimethylsiloxane (PDMS) substrates have been widely used in cell sheet engineering due to their low microfabrication cost, higher stability, excellent biocompatibility, and most importantly, ability to guide cellular growth and patterning. However, the current methods for PDMS surface modification either require a complicated procedure or generate a non-uniform surface coating, leading to the production of poor-quality cell layers. A simple and efficient surface coating method is critically needed to improve the uniformity and quality of the generated cell layers. Herein, a fast, simple and inexpensive surface coating method was analyzed for its ability to uniformly coat polydopamine (PD) with or without collagen on micro-grated PDMS substrates without altering essential surface topographical features. Topographical feature, stiffness and cytotoxicity of these PD and/or collagen based surface coatings were further analyzed. Results showed that the PD-based coating method facilitated aligned and uniform cell growth, therefore holds great promise for cell sheet engineering as well as completely biological tissue biomanufacturing.

One-Step Labeling of Collagen Hydrogels with Polydopamine and Manganese Porphyrin for Non-Invasive Scaffold Tracking on Magnetic Resonance Imaging

Biomaterial scaffolds are the cornerstone to supporting 3D tissue growth. Optimized scaffold design is critical to successful regeneration, and this optimization requires accurate knowledge of the scaffold's interaction with living tissue in the dynamic in vivo milieu. Unfortunately, non-invasive methods that can probe scaffolds in the intact living subject are largely underexplored, with imaging-based assessment relying on either imaging cells seeded on the scaffold or imaging scaffolds that have been chemically altered. In this work, the authors develop a broadly applicable magnetic resonance imaging (MRI) method to image scaffolds directly. A positive-contrast "bright" manganese porphyrin (MnP) agent for labeling scaffolds is used to achieve high sensitivity and specificity, and polydopamine, a biologically derived universal adhesive, is employed for adhering the MnP. The technique was optimized in vitro on a prototypic collagen gel, and in vivo assessment was performed in rats. The results demonstrate superior in vivo scaffold visualization and the potential for quantitative tracking of degradation over time. Designed with ease of synthesis in mind and general applicability for the continuing expansion of available biomaterials, the proposed method will allow tissue engineers to assess and fine-tune the in vivo behavior of their scaffolds for optimal regeneration.

Polydopamine/puerarin nanoparticle-incorporated hybrid hydrogels for enhanced wound healing

Oxidative damage generated would disrupt the oxidant/antioxidant balance in cells, causing slow wound healing and tissue regeneration. Hydrogel dressing with antioxidant properties can promote wound healing, however, its design is still a challenge.

Preparation of mussel-inspired injectable hydrogels based on dual-functionalized alginate with improved adhesive, self-healing, and mechanical properties

A novel mussel-inspired injectable hydrogel based on catechol- and aldehyde-modified alginate was developed, which avoided the introduction of small molecular oxidants and preserved the catechol functional groups.

Polydopamine-collagen complex to enhance the biocompatibility of polydimethylsiloxane substrates for sustaining long-term culture of L929 fibroblasts and tendon stem cells

Polydimethylsiloxane (PDMS) is a commercialized polymer extensively used in the fabrication of versatile microfluidic microdevices for studies in cell biology and tissue engineering. However, the inherent surface hydrophobicity of PDMS is not optimal for cell culture and thus restrains its applications for investigation of long-term behaviors of fibroblasts and stem cells. To improve the surface biocompatibility of PDMS, a facile technique was developed by modifying the PDMS surface with polydopamine-collagen (COL/PDA) complex. The successful synthesis of COL/PDA was verified through proton nuclear magnetic resonance spectroscopy. Compared to surface coating solely with COL or PDA, the surface wettability was significantly improved on COL/PDA-modified PDMS substrates based on water contact angle characterizations. The modified PDMS surface remarkably enhanced the initial adhesion and long-term proliferation of L929 fibroblasts and tendon stem cells (TSCs). Additionally, the effects of COL/PDA coating on cell viability and apoptosis were further investigated under prolonged incubation. We found that the COL/PDA coating on PDMS resulted in a substantial increase of cell viability compared to native PDMS, and the cell apoptosis was considerably impeded on the modified PDMS. This study demonstrated that COL/PDA coating can effectively enhance the surface biocompatibility of PDMS as verified by the enhanced adhesion and long-term proliferation of L929 fibroblasts and TSCs. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 408-418, 2018.

Insights into the rheological behaviors evolution of alginate dialdehyde crosslinked collagen solutions evaluated by numerical models

The elaboration of the rheological behaviors of alginate dialdehyde (ADA) crosslinked collagen solutions, along with the quantitative analysis via numerical models contribute to the controllable design of ADA crosslinked solution system's fluid mechanics performance during manufacturing process for collagen biomaterials. In the present work, steady shear flow, dynamical viscoelasticity, creep-recovery, thixotropy tests were performed to characterize the rheological behaviors of the collagen solutions incorporating of ADA from the different aspects and fitted with corresponding numerical models. It was found that pseudoplastic properties of all samples enhanced with increasing amounts of ADA, which was confirmed by the parameters calculated from the Ostwald-de Waele model, Carreau and Cross model, for instance, the non-Newtonian index (n) decreased from 0.786 to 0.201 and a great increase by 280 times in value of viscosity index (K) was obtained from Ostwald-de Waele model. The forth-mode Leonov model was selected to fit all dynamic modulus-frequency curves due to its higher fitting precision (R²>0.99). It could be found that the values of correlation shear viscosity (η_k) increased and the values of relaxation time (θ_k) decreased with increasing ADA at the fixed k value, suggesting that the incorporation of ADA accelerated the transformation of the collagen solutions from liquid-like to gel-like state due to more formation of CN linkages between aldehyde groups and lysine residues. Also, the curves of creep and recovery phase of the native and crosslinked collagen solutions were simulated well using Burger model and a semi-empirical model, respectively. The ability to resist to deformation and elasticity strengthened for the samples with higher amounts of ADA, accompanied with the important fact that compliance value (J₅₀) decreased from 56.317Pa^-1 to 2.135Pa^-1 and the recovery percentage (R_creep) increased from 2.651% to 28.217%. Finally, it was found that the area of thixotropic loop increased from 8.942Pa/s to 17.823Pa/s with increasing introduction of ADA, suggesting that stronger thixotropic behavior was associated with higher amount of ADA. Furthermore, Herschel-Bulkley model was employed to describe the up and down curves of all samples and it was confirmed that all collagen solutions belonged to pseudoplastic fluid (the flow index<1) without apparent yield stress and shear-thinning behaviors were more obvious with increasing additions of ADA according to the increasing consistency coefficient K values. Overall, this work contributed a new insight into the interactions between collagen and ADA based on quantitative rheological methods reflecting the different rheological properties and the results obtained should be of great utility in the extensive application of ADA crosslinked collagen solutions into diverse collagen-based materials.

ECM–oligourethene–silica hydrogels as a local drug release system of dexamethasone for stimulating macrophages

The incorporation of silica particles inside of extracellular matrix hydrogels supports the loading and releasing of dexamethasone, a therapeutic for modulating macrophage.