Evaluation of dense collagen matrices as medicated wound dressing for the treatment of cutaneous chronic wounds

Sclerostin Antibody-Loaded Dense Collagen Hydrogels Promote Critical-Size Bone Defect Repair

The management of extensive bone loss remains a clinical challenge. Numerous studies are underway to develop a combination of biomaterials, biomolecules, and stem cells to address this challenge. In particular, the systemic administration of antibodies against sclerostin, a regulator of bone formation, was recently shown to enhance the bone repair efficiency of dense collagen hydrogels (DCHs) hosting murine dental pulp stem cells (mDPSCs). The aim of the present study was to assess whether these antibodies, encapsulated and released from DCHs, could promote craniofacial bone repair by the local inhibition of sclerostin. In vitro studies showed that antibody loading modified neither the hydrogel structure nor the viability of seeded mDPSCs. When implanted in a mouse calvaria critical-size bone defect, antibody-loaded DCHs showed repair capabilities similar to those of acellular unloaded DCHs combined with antibody injections. Importantly, the addition of mDPSCs provided no further benefit. Altogether, the local delivery of antisclerostin antibodies from acellular dense collagen scaffolds is highly effective for bone repair. The drastic reduction in the required amount of antibody compared to systemic injection should reduce the cost of the procedure, making the strategy proposed here a promising therapeutic approach for large bone defect repair.

Hemp Protein Isolate-Based Natural Thermal-Reversible Hydrogel as a Novel Wound Dressing Material

Hydrogels, due to their excellent microstructure and mechanical strength, have become a novel biomaterial in wound dressing. However, plant proteins have never been considered because of their poor original gelling performances and insufficient rheological properties. Here, we reported the fabrication of a plant protein-based thermal-reversible gel using a reverse micelle-extracted hemp protein isolate (HPI). A systematic study was conducted to fully reveal their microstructure, rheological properties, and anti-inflammatory effect to lay a foundation for this newly developed plant protein hydrogel as a potential natural wound dressing. By modulating protein concentration (4% HPI) and temperature (85 °C), a thermal-reversible HPI gel appeared as a filament structure with the major molecular driving force of hydrophobic interactions and hydrogen bonds. By characterizing the rheological properties, lower gel strength and wider linear viscoelastic regime were determined in the thermal-reversible HPI gel compared with a thermal-irreversible HPI gel. Besides, large amplitude oscillatory shear data identified the thermal-reversible gel as a soft gel which demonstrated intracycle strain stiffening and shear thinning behavior. Moreover, the thermal-reversible HPI gel is nontoxic and has benefits in neutrophil growth with injectability and perfect wound coverage. This study opens a novel means to form a natural thermal-reversible hydrogel that can be a new material source for wound dressing.

Silver nanoparticles loaded triple-layered cellulose-acetate based multifunctional dressing for wound healing

Chronic wounds present considerable challenges which delay their effective healing. Currently, there are several biomaterial-based wound dressings available for healing diverse wound types. However, most of commercial wound dressings are too expensive to be affordable to the patients belonging to the middle and lower socioeconomic strata of the society. Thus, in this investigation affordable triple layered nanofibrous bandages were fabricated using the layer-by-layer approach. Here, the topmost layer comprised of a hydrophilic poly vinyl alcohol layer, cross-linked with citric acid. The middle layer comprising of cellulose acetate was loaded with silver nanoparticles as an antibacterial agent, while the lowermost layer was fabricated using hydrophobic polycaprolactone. The triple-layered nanofibrous bandages having a nano-topography, exhibited a smooth, uniform and bead-free morphology, with the nanofiber diameter ranging between 200 and 300 nm. The nanofibers demonstrated excellent wettability, slow in vitro degradation, controlled release of nano‑silver and potent antibacterial activity against Gram-negative (E.coli) and Gram-positive (S. aureus) bacteria. The fabricated bandages had excellent mechanical strength upto 12.72 ± 0.790 M. Pa, which was suitable for biomedical and tissue engineering applications. The bandage demonstrated excellent in vitro hemocompatibility and biocompatibility. In vivo excisional wound contraction, along with H and E and Masson's Trichrome staining further confirmed the potential of the nanofibrous bandage for full-thickness wound healing. Pre-clinical investigations thus indicated the possibility of further evaluating the triple-layered nanofibrous dressing in clinical settings.

Streamlining Skin Regeneration: A Ready-To-Use Silk Bilayer Wound Dressing

Silk proteins have been highlighted in the past decade for tissue engineering (TE) and skin regeneration due to their biocompatibility, biodegradability, and exceptional mechanical properties. While silk fibroin (SF) has high structural and mechanical stability with high potential as an external protective layer, traditionally discarded sericin (SS) has shown great potential as a natural-based hydrogel, promoting cell-cell interactions, making it an ideal material for direct wound contact. In this context, the present study proposes a new wound dressing approach by developing an SS/SF bilayer construct for full-thickness exudative wounds. The processing methodology implemented included an innovation element and the cryopreservation of the SS intrinsic secondary structure, followed by rehydration to produce a hydrogel layer, which was integrated with a salt-leached SF scaffold to produce a bilayer structure. In addition, a sterilization protocol was developed using supercritical technology (sCO2) to allow an industrial scale-up. The resulting bilayer material presented high porosity (>85%) and interconnectivity while promoting cell adhesion, proliferation, and infiltration of human dermal fibroblasts (HDFs). SS and SF exhibit distinct secondary structures, pore sizes, and swelling properties, opening new possibilities for dual-phased systems that accommodate the different needs of a wound during the healing process. The innovative SS hydrogel layer highlights the transformative potential of the proposed bilayer system for biomedical therapeutics and TE, offering insights into novel wound dressing fabrication.

Biomaterials-Based Antioxidant Strategies for the Treatment of Oxidative Stress Diseases

Oxidative stress is characterized by an increase in reactive oxygen species or a decrease in antioxidants in the body. This imbalance leads to detrimental effects, including inflammation and multiple chronic diseases, ranging from impaired wound healing to highly impacting pathologies in the neural and cardiovascular systems, or the bone, amongst others. However, supplying compounds with antioxidant activity is hampered by their low bioavailability. The development of biomaterials with antioxidant capacity is poised to overcome this roadblock. Moreover, in the treatment of chronic inflammation, material-based strategies would allow the controlled and targeted release of antioxidants into the affected tissue. In this review, we revise the main causes and effects of oxidative stress, and survey antioxidant biomaterials used for the treatment of chronic wounds, neurodegenerative diseases, cardiovascular diseases (focusing on cardiac infarction, myocardial ischemia-reperfusion injury and atherosclerosis) and osteoporosis. We anticipate that these developments will lead to the emergence of new technologies for tissue engineering, control of oxidative stress and prevention of diseases associated with oxidative stress.

Hydrophobic Tetracycline Immobilized in Fibrous Hyaluronan Regulates Adhesive Collagen-Based Hydrogel Stability for Infected Wound Healing

Collagen-based hydrogels have a significant impact on wound healing, but they suffer from structural instability and bacterial invasion in infected wounds. Here, electrospun nanofibers of esterified hyaluronan (HA-Bn/T) are developed to immobilize the hydrophobic antibacterial drug tetracycline by π-π stacking interaction. Dopamine-modified hyaluronan and HA-Bn/T are employed simultaneously to stabilize the structure of collagen-based hydrogel by chemically interweaving the collagen fibril network and decreasing the rate of collagen degradation. This renders it injectable for in situ gelation, with suitable skin adhesion properties and long-lasting drug release capability. This hybridized interwoven hydrogel promotes the proliferation and migration of L929 cells and vascularization in vitro. It presents satisfactory antibacterial ability against Staphylococcus aureus and Escherichia coli. The structure also retains the functional protein environment provided by collagen fiber, inhibits the bacterial environment of infected wounds, and modulates local inflammation, resulting in neovascularization, collagen deposition, and partial follicular regeneration. This strategy offers a new solution for infected wound healing.

UV cross-linked injectable non-swelling dihydrocaffeic acid grafted chitosan hydrogel for promoting wound healing

Hydrogels are widely used as wound dressings for wound healing, but when hydrogels absorb wound exudate, swelling occurs and compresses the surrounding tissue, affecting healing. A chitosan injectable (CS/4-PA/CAT) hydrogel based on catechol and 4-glutenoic acid was prepared to avoid swelling and promote wound healing. After cross-linking by UV light, pentenyl groups formed hydrophobic alkyl chains which give the hydrogel a hydrophobic network and thus control its swelling. CS/4-PA/CAT hydrogels retained their non-swelling for a long time in PBS solution at 37 °C. CS/4-PA/CAT hydrogels had good injectable and adhesive properties, and had a good killing effect on E. coli and S. aureus and could remove the bacterial biofilms of E. coli and S. aureus. CS/4-PA/CAT hydrogels had good in vitro coagulation function by absorbing red blood cells and platelets. When used in a whole skin injury model, CS/4-PA/CAT-1 hydrogel stimulated fibroblast migration, promoted epithelialization and accelerated collagen deposition to promote defect healing, and showed good hemostatic effects in liver and femoral artery defects in mice. In summary, the non-swelling injectable hydrogel with free radical scavenging, rapid hemostasis, and antibacterial effects would be a promising treatment for defect repair.

Wearable Smart Bandage-Based Bio-Sensors

Bandage is a well-established industry, whereas wearable electronics is an emerging industry. This review presents the bandage as the base of wearable bioelectronics. It begins with introducing a detailed background to bandages and the development of bandage-based smart sensors, which is followed by a sequential discussion of the technical characteristics of the existing bandages, a more practical methodology for future applications, and manufacturing processes of bandage-based wearable biosensors. The review then elaborates on the advantages of basing the next generation of wearables, such as acceptance by the customers and system approvals, and disposal.

Anisotropic dense collagen hydrogels with two ranges of porosity to mimic the skeletal muscle extracellular matrix

Despite the crucial role of the extracellular matrix (ECM) in the organotypic organization and function of skeletal muscles, most 3D models do not mimic its specific characteristics, namely its biochemical composition, stiffness, anisotropy, and porosity. Here, a novel 3D in vitro model of muscle ECM was developed reproducing these four crucial characteristics of the native ECM. An anisotropic hydrogel mimicking the muscle fascia was obtained thanks to unidirectional 3D printing of dense collagen with aligned collagen fibrils. The space between the different layers was tuned to generate an intrinsic network of pores (100 μm) suitable for nutrient and oxygen diffusion. By modulating the gelling conditions, the mechanical properties of the construct reached those measured in the physiological muscle ECM. This artificial matrix was thus evaluated for myoblast differentiation. The addition of large channels (600 μm) by molding permitted to create a second range of porosity suitable for cell colonization without altering the physical properties of the hydrogel. Skeletal myoblasts embedded in Matrigel®, seeded within the channels, organized in 3D, and differentiated into multinucleated myotubes. These results show that porous and anisotropic dense collagen hydrogels are promising biomaterials to model skeletal muscle ECM.

Collagen-based hydrogels cross-linked via laccase - mediated system incorporated with Fe3+ for wound dressing

Pure fish skin collagen hydrogels as a wound dressing have lower thermodynamic stability than mammalian collagen and usually suffer from poor mechanical properties, weak degradation resistance and insufficient functionalities such as antioxidant and anti-inflammatory properties to meet clinical needs that limit its further application. Here, a silver carp skin collagen hydrogel is successfully constructed via the cross-linking of the laccase-protocatechuic aldehyde (LAC-PAL) and the structure of the hydrogel is further consolidated and strengthened by the interaction of PAL and Fe3+. In this collagen hydrogel system, Fe3+, acting as a second cross-linker, consolidates and enhances the stability of the hydrogel after LAC-PAL cross-linking. This cross-linking method improves the resistance to degradation with a reduction in its degradation rate from 89.45% to 38.66% and endows the hydrogel with antioxidant activity. The in vitro data show that the hydrogel promotes cell proliferation and adhesion exhibiting good biocompatibility. Animal experiments show that the hydrogel contributes to angiogenesis and improves inflammatory response in the early stages of wound healing, resulting in promoting wound healing. Altogether, this newly developed collagen hydrogel is expected to be applied in wound repair as a wound dressing.

A Comprehensive Review on Collagen Type I Development of Biomaterials for Tissue Engineering: From Biosynthesis to Bioscaffold

Collagen is the most abundant structural protein found in humans and mammals, particularly in the extracellular matrix (ECM). Its primary function is to hold the body together. The collagen superfamily of proteins includes over 20 types that have been identified. Yet, collagen type I is the major component in many tissues and can be extracted as a natural biomaterial for various medical and biological purposes. Collagen has multiple advantageous characteristics, including varied sources, biocompatibility, sustainability, low immunogenicity, porosity, and biodegradability. As such, collagen-type-I-based bioscaffolds have been widely used in tissue engineering. Biomaterials based on collagen type I can also be modified to improve their functions, such as by crosslinking to strengthen the mechanical property or adding biochemical factors to enhance their biological activity. This review discusses the complexities of collagen type I structure, biosynthesis, sources for collagen derivatives, methods of isolation and purification, physicochemical characteristics, and the current development of collagen-type-I-based scaffolds in tissue engineering applications. The advancement of additional novel tissue engineered bioproducts with refined techniques and continuous biomaterial augmentation is facilitated by understanding the conventional design and application of biomaterials based on collagen type I.

Generation of an Adequate Perfusion Network within Dense Collagen Hydrogels Using Thermoplastic Polymers as Sacrificial Matrix to Promote Cell Viability

Dense collagen hydrogels are promising biomaterials for several tissue-engineering applications. They exhibit high mechanical properties, similar to physiological extracellular matrices, and do not shrink under cellular activity. However, they suffer from several drawbacks, such as weak nutrient and O₂ diffusion, impacting cell survival. Here, we report a novel strategy to create a perfusion system within dense and thick collagen hydrogels to promote cell viability. The 3D printing of a thermoplastic filament (high-impact polystyrene, HIPS) with a three-wave shape is used to produce an appropriate sacrificial matrix. The HIPS thermoplastic polymer allows for good shape fidelity of the filament and does not collapse under the mechanical load of the collagen solution. After the collagen gels around the filament and dissolves, a channel is generated, allowing for adequate and rapid hydrogel perfusion. The dissolution process does not alter the collagen hydrogel’s physical or chemical properties, and the perfusion is associated with an increased fibroblast survival. Here, we report the novel utilization of thermoplastics to generate a perfusion network within biomimetic collagen hydrogels.

Biomimetic Silk Macroporous Materials for Drug Delivery Obtained via Ice-Templating

Silk from Bombyx mori is one of the most exciting materials in nature. The apparently simple arrangement of its two major components─two parallel filaments of silk fibroin (SF) coated by a common sericin (SS) sheath─provides a combination of mechanical and surface properties that can protect the moth during its most vulnerable phase, the pupal stage. Here, we recapitulate the topology of native silk fibers but shape them into three-dimensional porous constructs using an unprecedented design strategy. We demonstrate, for the first time, the potential of these macroporous silk foams as dermal patches for wound protection and for the controlled delivery of Rifamycin (Rif), a model antibiotic. The method implies (i) removing SS from silk fibers; (ii) shaping SF solutions into macroporous foams via ice-templating; (iii) stabilizing the SF macroporous foam in a methanolic solution of Rif; and (iv) coating Rif-loaded SF foams with a SS sheath. The resulting SS@SF foams exhibit water wicking capacity and accommodate up to ∼20% deformation without detaching from a skin model. The antibacterial behavior of Rif-loaded SS@SF foams against Staphylococcus aureus on agar plates outperforms that of SF foams (>1 week and 4 days, respectively). The reassembly of natural materials as macroporous foams─illustrated here for the reconstruction of silk-based materials─can be extended to other multicomponent natural materials and may play an important role in applications where controlled release of molecules and fluid transport are pivotal.

Synthesis of Fibrin-Type I Collagen Biomaterials via an Acidic Gel

Fibrin-Type I collagen composite gels have been widely studied as biomaterials, in which both networks are usually formed simultaneously at a neutral pH. Here, we describe a new protocol in which mixed concentrated solutions of collagen and fibrinogen were first incubated at acidic pH to induce fibrinogen gel formation, followed by a pH change to neutral inducing collagen fiber formation. Thrombin was then added to form fibrin-collagen networks. Using this protocol, mixed gels containing 20 mg.mL⁻¹ fibrin and up to 10 mg.mL⁻¹ collagen could be prepared. Macroscopic observations evidenced that increasing the content of collagen increases the turbidity of the gels and decreases their shrinkage during the fibrinogen-to-fibrin conversion. The presence of collagen had a minor influence on the rheological properties of the gels. Electron microscopy allowed for observation of collagen fibers within the fibrin network. 2D cultures of C2C12 myoblasts on mixed gels revealed that the presence of collagen favors proliferation and local alignment of the cells. However, it interferes with cell differentiation and myotube formation, suggesting that further control of in-gel collagen self-assembly is required to elaborate fully functional biomaterials.

Smart 3D Printed Hydrogel Skin Wound Bandages: A Review

Wounds are a major health concern affecting the lives of millions of people. Some wounds may pass a threshold diameter to become unrecoverable by themselves. These wounds become chronic and may even lead to mortality. Recently, 3D printing technology, in association with biocompatible hydrogels, has emerged as a promising platform for developing smart wound dressings, overcoming several challenges. 3D printed wound dressings can be loaded with a variety of items, such as antibiotics, antibacterial nanoparticles, and other drugs that can accelerate wound healing rate. 3D printing is computerized, allowing each level of the printed part to be fully controlled in situ to produce the dressings desired. In this review, recent developments in hydrogel-based wound dressings made using 3D printing are covered. The most common biosensors integrated with 3D printed hydrogels for wound dressing applications are comprehensively discussed. Fundamental challenges for 3D printing and future prospects are highlighted. Additionally, some related nanomaterial-based hydrogels are recommended for future consideration.

Multifunctional Gelatin/Chitosan Electrospun Wound Dressing Dopped with Undaria pinnatifida Phlorotannin-Enriched Extract for Skin Regeneration

The similarities of electrospun fibers with the skin extracellular matrix (ECM) make them promising structures for advanced wound dressings. Moreover, infection and resistance in wounds are a major health concern that may be reduced with antibacterial wound dressings. In this work, a multifunctional wound dressing was developed based on gelatin/chitosan hybrid fibers dopped with phlorotannin-enrich extract from the seaweed Undaria pinnatifida. The intrinsic electrospun structure properties combined with the antimicrobial and anti-inflammatory properties of phlorotannin-enrich extract will enhance the wound healing process. Electrospun meshes were produced by incorporating 1 or 2 wt% of extract, and the structure without extract was used as a control. Physico-chemical, mechanical, and biological properties were evaluated for all conditions. Results demonstrated that all developed samples presented a homogenous fiber deposition with the average diameters closer to the native ECM fibrils, and high porosities (~90%) that will be crucial to control the wound moist environment. According to the tensile test assays, the incorporation of phlorotannin-enriched extract enhances the elastic performance of the samples. Additionally, the extract incorporation made the structure stable over time since its in vitro degradation rates decreased under enzymatic medium. Extract release profile demonstrated a longstanding delivery (up to 160 days), reaching a maximum value of ~98% over time. Moreover, the preliminary antimicrobial results confirm the mesh's antimicrobial activity against Pseudomonas aeruginosa and Staphylococcus aureus. In terms of biological characterization, no condition presented cytotoxicity effects on hDNF cells, allowing their adhesion and proliferation over 14 days, except the condition of 2 wt% after 7 days. Overall, the electrospun structure comprising phlorotannins-enriched extract is a promising bioactive structure with potential to be used as a drug delivery system for skin regeneration by reducing the bacterial infection in the wound bed.

Antimicrobial and physicochemical characterization of 2,3-dialdehyde cellulose-based wound dressings systems

Biobased and biodegradable films were prepared by physically mixing 2,3-dialdehyde cellulose (DAC) with two other biopolymers, zein and gelatin, in three different proportions. The antimicrobial activities of the composite blends against Gram-positive and Gram-negative bacteria increase with the increase of DAC content. Cell viability tests on mammalian cells showed that the materials were not cytotoxic. In addition, DAC and gelatin were able to promote thermal degradation of the blends. However, DAC increased the stiffness and decreased the glass transition temperature of the blends, while gelatin was able to decrease the stiffness of the film. Morphological analysis showed the effect of DAC on the surface smoothness of the blends. The contact angle confirmed that all blends were within the range of hydrophilic materials. Although all the blends showed impressive performance for wound dressing application, the blend with gelatin might be more suitable for this purpose due to its better mechanical performance and antibacterial activity.

Natural-Based Biomaterial for Skin Wound Healing (Gelatin vs. Collagen): Expert Review

Collagen (Col) and gelatin are most extensively used in various fields, particularly in pharmaceuticals and therapeutics. Numerous researchers have proven that they are highly biocompatible to human tissues, exhibit low antigenicity and are easy to degrade. Despite their different sources both Col and gelatin have almost the same effects when it comes to wound healing mechanisms. Considering this, the bioactivity and biological effects of both Col and gelatin have been, and are being, constantly investigated through in vitro and in vivo assays to obtain maximum outcomes in the future. With regard to their proven nutritional values as sources of protein, Col and gelatin products exert various possible biological activities on cells in the extracellular matrix (ECM). In addition, a vast number of novel Col and gelatin applications have been discovered. This review compared Col and gelatin in terms of their structures, sources of derivatives, physicochemical properties, results of in vitro and in vivo studies, their roles in wound healing and the current challenges in wound healing. Thus, this review provides the current insights and the latest discoveries on both Col and gelatin in their wound healing mechanisms.

USPIO-PEG nanoparticles functionalized with a highly specific collagen-binding peptide: a step towards MRI diagnosis of fibrosis

Fibrosis is characterized by a pathologic deposition of collagen I, leading to impaired function of organs. Tissue biopsy is the gold standard method for the diagnosis of fibrosis but this is an invasive procedure, subject to sampling errors. Several non-invasive techniques such as magnetic resonance imaging (MRI) using non-specific probes have been developed but they are not fully satisfying as they allow diagnosis at a late stage. In this study, collagelin, a collagen-binding peptide has been covalently linked using click chemistry to pegylated Ultra Small Super Paramagnetic Iron Oxide Nanoparticles (USPIO-PO-PEG-collagelin NPs) with the aim of diagnosing fibrosis at an early stage by MRI. USPIO-PO-PEG-collagelin NPs showed a high affinity for collagen I, two times higher than that of free collagelin whereas not peptide labeled USPIO NPs (USPIO-PO-PEG-yne) did not present any affinity. NPs were not toxic for macrophages and fibroblasts. Diffusion through collagen hydrogels concentrated at 3 and 10 mg mL-1 revealed a large accumulation of USPIO-PO-PEG-collagelin NPs within the collagen network after 72 hours, ca. 3 times larger than that of unlabeled USPIO, thereby evidencing the specific targeting of collagen I. Moreover, the quantity of USPIO-PO-PEG-collagelin NPs accumulated within hydrogels was proportional to the collagen concentration. Subsequently, the NPs diffusion through collagen hydrogels was monitored by MRI. The MRI T2 time relaxation decreased much more significantly with depth for USPIO-PO-PEG-collagelin NPs compared to unlabeled ones. Taken together, these results show that USPIO-PEG-collagelin NPs are promising as effective MRI nanotracers for molecular imaging of fibrosis at an early stage.

Curdlan-Based Hydrogels for Potential Application as Dressings for Promotion of Skin Wound Healing-Preliminary In Vitro Studies

The aim of this work was to establish whether novel curdlan-based hydrogels enriched with Ca²⁺ ions may be considered as potential candidates for dressings, for the acceleration of skin wound healing. Firstly, biomaterials were allocated for evaluation of structural and mechanical properties. Subsequently, the ability of hydrogels to absorb simulated wound fluid and water vapor permeability, as well their capacity to release calcium ions, was evaluated. The biocompatibility of biomaterials was assessed using normal human skin fibroblasts. Importantly, the main features of the obtained curdlan-based hydrogels were compared with those of KALTOSTAT^® (a commercial calcium sodium alginate wound dressing). The obtained results showed that curdlan-based biomaterials possessed a mesoporous structure (pore diameter ranged from 14–48 nm) and exhibited a good ability to absorb simulated wound fluid (swelling ratio close to 974–1229%). Moreover, in a wet state, they enabled proper water vapor transmission rate (>2000 g/m²/day), thanks to their hydrogel structure. Finally, it was found that biomaterial composed of 11 wt.% of curdlan (Cur_11%) possessed the most desirable biological properties in vitro. It released a beneficial amount of calcium ions to the aqueous environment (approximately 6.12 mM), which significantly enhanced fibroblast viability and proliferation. Taking into account the beneficial properties of Cur_11% biomaterial, it seems justified to subject it to more advanced cell culture experiments in vitro and to in vivo studies in order to determine its precise influence on skin wound healing.

Incorporating a structural extracellular matrix gradient into a porcine urinary bladder matrix-based hydrogel dermal scaffold

The increasing prevalence of chronic, nonhealing wounds necessitates the investigation of full-thickness skin substitutes conducive to host integration and wound closure. Extracellular matrix (ECM)-based hydrogel scaffolds mimic the physiological matrix environment of dermal cells, thereby conferring favorable cellular adhesion, infiltration, and proliferation. However, low-concentration ECM hydrogels rapidly lose mechanical strength as they degrade, leaving them susceptible to shrinkage from fibroblast-mediated contraction. Conversely, high-concentration ECM hydrogels are typically too dense to permit nutrient diffusion and cellular migration. This study investigates the design and fabrication of a graded-concentration hydrogel composed of porcine urinary bladder matrix (UBM) as a dermal scaffold for potential use in chronic wound treatment. Our method of UBM isolation and decellularization effectively removed native DNA while preserving matrix proteins. Hydrogels composed of a range of decellularized UBM (dUBM) concentrations were characterized and used to design a three-tiered gradient hydrogel that promoted cellular activity and maintained structural integrity. The gradient dUBM hydrogel showed stability of cross-sectional area during collagenase degradation, despite considerable loss of mass. The gradient dUBM hydrogel also resisted fibroblast-mediated contraction while supporting high surface cell viability, demonstrating the mechanical support provided by denser layers of dUBM. Overall, incorporation of an ECM concentration gradient into a porcine UBM-based hydrogel scaffold capitalizes on the unique advantages of both high and low-concentration ECM hydrogels, and mitigates the structural weaknesses that have limited the efficacy of hydrogel dermal scaffolds for chronic wounds. Our gradient design shows promise for future development of stable, pro-regenerative wound scaffolds with customized architectures using 3D printing.

Nanostructured Dense Collagen-Polyester Composite Hydrogels as Amphiphilic Platforms for Drug Delivery

Associating collagen with biodegradable hydrophobic polyesters constitutes a promising method for the design of medicated biomaterials. Current collagen-polyester composite hydrogels consisting of pre-formed polymeric particles encapsulated within a low concentrated collagen hydrogel suffer from poor physical properties and low drug loading. Herein, an amphiphilic composite platform associating dense collagen hydrogels and up to 50 wt% polyesters with different hydrophobicity and chain length is developed. An original method of fabrication is disclosed based on in situ nanoprecipitation of polyesters impregnated in a pre-formed 3D dense collagen network. Composites made of poly(lactic-co-glycolic acid) (PLGA) and poly(lactic acid) (PLA) but not polycaprolactone (PCL) exhibit improved mechanical properties compared to those of pure collagen dense hydrogels while keeping a high degree of hydration. Release kinetics of spironolactone, a lipophilic steroid used as a drug model, can be tuned over one month. No cytotoxicity of the composites is observed on fibroblasts and keratinocytes. Unlike the incorporation of pre-formed particles, the new process allows for both improved physical properties of collagen hydrogels and controlled drug delivery. The ease of fabrication, wide range of accessible compositions, and positive preliminary safety evaluations of these collagen-polyesters will favor their translation into clinics in wide areas such as drug delivery and tissue engineering.

Nanotechnology Development for Formulating Essential Oils in Wound Dressing Materials to Promote the Wound-Healing Process: A Review

Wound healing refers to the replacement of damaged tissue through strongly coordinated cellular events. The patient’s condition and different types of wounds complicate the already intricate healing process. Conventional wound dressing materials seem to be insufficient to facilitate and support this mechanism. Nanotechnology could provide the physicochemical properties and specific biological responses needed to promote the healing process. For nanoparticulate dressing design, growing interest has focused on natural biopolymers due to their biocompatibility and good adaptability to technological needs. Polysaccharides are the most common natural biopolymers used for wound-healing materials. In particular, alginate and chitosan polymers exhibit intrinsic antibacterial and anti-inflammatory effects, useful for guaranteeing efficient treatment. Recent studies highlight that several natural plant-derived molecules can influence healing stages. In particular, essential oils show excellent antibacterial, antifungal, antioxidant, and anti-inflammatory properties that can be amplified by combining them with nanotechnological strategies. This review summarizes recent studies concerning essential oils as active secondary compounds in polysaccharide-based wound dressings.

Core-Shell Pure Collagen Threads Extruded from Highly Concentrated Solutions Promote Colonization and Differentiation of C3H10T1/2 Cells

The elaboration of scaffolds able to efficiently promote cell differentiation toward a given cell type remains challenging. Here, we engineered dense type I collagen threads with the aim of providing scaffolds with specific morphological and mechanical properties for C3H10T1/2 mesenchymal stem cells. Extrusion of pure collagen solutions at different concentrations (15, 30, and 60 mg/mL) in a PBS 5× buffer generated dense fibrillated collagen threads. For the two highest concentrations, threads displayed a core-shell structure with a marked fibril orientation of the outer layer along the longitudinal axis of the threads. Young's modulus and ultimate tensile stress as high as 1 and 0.3 MPa, respectively, were obtained for the most concentrated collagen threads without addition of any cross-linkers. C3H10T1/2 cells oriented themselves with a mean angle of 15-24° with respect to the longitudinal axis of the threads. Cells penetrated the 30 mg/mL scaffolds but remained on the surface of the 60 mg/mL ones. After three weeks of culture, cells displayed strong expression of the tendon differentiation marker Tnmd, especially for the 30 mg/mL threads. These results suggest that both the morphological and mechanical characteristics of collagen threads are key factors in promoting C3H10T1/2 differentiation into tenocytes, offering promising levers to optimize tissue engineering scaffolds for tendon regeneration.

Polymer-based biomaterials for chronic wound management: Promises and challenges

Chronic non-healing wounds tender a great challenge to patients, physicians, and wound care professionals. In view of the increasing prevalence of chronic wounds due to ischemia, diabetic foot, venous, and pressure ulcers, their appropriate management requires significant attention. Along with the basic techniques of medical and surgical treatments; an ideal dressing is essential for a speedy recovery and rapid healing of such wounds. Mechanistic understanding of chronic wound pathology will not only help towards future directions for an ideal dressing model but also to resonant advance research related to specific dressings for various wound types. This review provides key insights into causes, pathophysiology, and critical issues pertaining to chronic wounds and their management. It also summarizes the challenges faced for chronic wound treatment and specified factors responsible for delayed healing. Moreover, this review delivers a detailed discussion on available polymeric materials (alginate, chitosan, hyaluronic acid, collagen, polyurethane, cellulose, dextran, gelatin, silk, and polyaniline), their functional characteristics, and usage as chronic wound healing agents for polymeric wound dressing development. Incorporation and comparison of the research studies for their thermal behavior, structural analysis, and microscopic studies by Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy, respectively and swelling studies of different polymeric materials are discussed. Additionally, studies of anatomy cum physiology of wound healing, pathophysiology, tissue engineering and advance healing management approaches makes the content of this review a significant tool for future studies on chronic wounds healing by polymeric wound dressings. In this review, polymeric wound dressings have been explained in terms of their structures, function, chemistry, and key characteristics. These features are directly linked to the polymeric systems' potential in the management of chronic wounds. These polymeric systems have gained promising success in solving real word global health problems. More recently, innovative approaches to fabricate the polymer dressings have been introduced, but their commercial, sustainable, and high-scale production largely remains unexplored. This review also summarizes the promises of polymeric wound dressings and provides a future perspective on how the clinical and commercial landscape could potentially be propelled by utilizing polymers in wound care management.

Injectable Adhesive Self-Healing Multicross-Linked Double-Network Hydrogel Facilitates Full-Thickness Skin Wound Healing

The development of natural polymer-based hydrogels, combining outstanding injectability, self-healing, and tissue adhesion, with mechanical performance, able to facilitate full-thickness skin wound healing, remains challenging. We have developed an injectable micellar hydrogel (AF127/HA-ADH/OHA-Dop) with outstanding adhesive and self-healing properties able to accelerate full-thickness skin wound healing. Dopamine-functionalized oxidized hyaluronic acid (OHA-Dop), adipic acid dihydrazide-modified HA (HA-ADH), and aldehyde-terminated Pluronic F127 (AF127) were employed as polymer backbones. They were cross-linked in situ using Schiff base dynamic covalent bonds (AF127 micelle/HA-ADH network and HA-ADH/OHA-Dop network), hydrogen bonding, and π-π stacking interactions. The resulting multicross-linked double-network design forms a micellar hydrogel. The unique multicross-linked double-network structure endows the hydrogel with both improved injection abilities and mechanical performance while self-healing faster than single-network hydrogels. Inspired by mussel foot adhesive protein, OHA-Dop mimics the catechol groups seen in mussel proteins, endowing hydrogels with robust adhesion properties. We also demonstrate the potential of our hydrogels to accelerate full-thickness cutaneous wound closure and improve skin regeneration with reduced scarring. We anticipate that our hydrogel platform based on a novel multicross-linked double-network design will transform the future development of multifunctional wound dressings.

Sulfated chitosan rescues dysfunctional macrophages and accelerates wound healing in diabetic mice

Emerging evidence suggests that dysfunctional macrophages can cause chronic inflammation and impair tissue regeneration in diabetic wounds. Therefore, improving macrophage behaviors and functions may improve therapeutic outcomes of current treatments in diabetic wounds. Herein, we present a sulfated chitosan (SCS)-doped Collagen type I (Col I/SCS) hydrogel as a candidate for diabetic wound treatments, and assess its efficacy using streptozocin (STZ)-induced diabetic wound model. Results showed that Col I/SCS hydrogel significantly improved wound closure rate, collagen deposition, and revascularization in diabetic wounds. Flow cytometry analysis and immunofluorescent staining analysis showed that the Col I/SCS hydrogel accelerated the resolution of excessive inflammation by reducing the polarization of M1-like macrophages in chronic diabetic wounds. In addition, ELISA analysis revealed that the Col I/SCS hydrogel reduced the production of pro-inflammatory interleukin (IL)-6 and increased the production of anti-inflammatory cytokines including IL-4 and transforming growth factor-beta 1 (TGF-β1) during wound healing. Moreover, the Col I/SCS hydrogel enhanced the transdifferentiation of macrophages into fibroblasts, which enhanced the formation of collagen and the extracellular matrix (ECM) in wound tissue. We highlight a potential application of manipulating macrophages behaviors in the pathological microenvironment via materials strategy. STATEMENT OF SIGNIFICANCE: Improving the chronic inflammatory microenvironment of diabetic wounds by regulating macrophage behaviors has been of wide concern in recent years. We designed a Col I/SCS hydrogel based on Collagen type I and sulfated chitosan (SCS) without exogenous cells or cytokines, which could significantly improve angiogenesis and resolve chronic inflammation in diabetic wounds, and hence accelerate diabetic wound healing. The Col I/SCS hydrogel could facilitate the polarization of M1-to-M2 macrophages and activate the transdifferentiation of macrophages to fibroblasts. Additionally, the Col I/SCS hydrogel also equilibrated the content of pro-inflammatory and anti-inflammatory cytokines. This strategy may afford a new avenue to improve macrophage functions and accelerate diabetic chronic wound healing.

Type I Collagen-Fibrin Mixed Hydrogels: Preparation, Properties and Biomedical Applications

Type I collagen and fibrin are two essential proteins in tissue regeneration and have been widely used for the design of biomaterials. While they both form hydrogels via fibrillogenesis, they have distinct biochemical features, structural properties and biological functions which make their combination of high interest. A number of protocols to obtain such mixed gels have been described in the literature that differ in the sequence of mixing/addition of the various reagents. Experimental and modelling studies have suggested that such co-gels consist of an interpenetrated structure where the two proteins networks have local interactions only. Evidences have been accumulated that immobilized cells respond not only to the overall structure of the co-gels but can also exhibit responses specific to each of the proteins. Among the many biomedical applications of such type I collagen-fibrin mixed gels, those requiring the co-culture of two cell types with distinct affinity for these proteins, such as vascularization of tissue engineering constructs, appear particularly promising.

Chitin-Based Double-Network Hydrogel as Potential Superficial Soft-Tissue-Repairing Materials

Chitin is a biopolymer, which has been proven to be a biomedical material candidate, yet the weak mechanical properties seriously limit their potentials. In this work, a chitin-based double-network (DN) hydrogel has been designed as a potential superficial repairing material. The hydrogel was synthesized through a double-network (DN) strategy composing hybrid regenerated chitin nanofiber (RCN)-poly (ethylene glycol diglycidyl ether) (PEGDE) as the first network and polyacrylamide (PAAm) as the second network. The hybrid RCN-PEGDE/PAAm DN hydrogel was strong and tough, possessing Young's modulus (elasticity) E 0.097 ± 0.020 MPa, fracture stress σ_f 0.449 ± 0.025 MPa, and work of fracture W_f 5.75 ± 0.35 MJ·m^-3. The obtained DN hydrogel was strong enough for surgical requirements in the usage of soft tissue scaffolds. In addition, chitin endowed the DN hydrogel with good bacterial resistance and accelerated fibroblast proliferation, which increased the NIH3T3 cell number by nearly five times within 3 days. Subcutaneous implantation studies showed that the DN hydrogel did not induce inflammation after 4 weeks, suggesting a good biosafety in vivo. These results indicated that the hybrid RCN-PEGDE/PAAm DN hydrogel had great prospect as a rapid soft-tissue-repairing material.

Scaffolds for Wound Healing Applications

In order to overcome the shortcomings related to unspecific and partially efficient conventional wound dressings, impressive efforts are oriented in the development and evaluation of new and effective platforms for wound healing applications. In situ formed wound dressings provide several advantages, including proper adaptability for wound bed microstructure and architecture, facile application, patient compliance and enhanced therapeutic effects. Natural or synthetic, composite or hybrid biomaterials represent suitable candidates for accelerated wound healing, by providing proper air and water vapor permeability, structure for macro- and microcirculation, support for cellular migration and proliferation, protection against microbial invasion and external contamination. Besides being the most promising choice for wound care applications, polymeric biomaterials (either from natural or synthetic sources) may exhibit intrinsic wound healing properties. Several nanotechnology-derived biomaterials proved great potential for wound healing applications, including micro- and nanoparticulate systems, fibrous scaffolds, and hydrogels. The present paper comprises the most recent data on modern and performant strategies for effective wound healing.

Advances and Impact of Antioxidant Hydrogel in Chronic Wound Healing

The accelerating and thorough treatment of chronic wounds still represents a major unmet medical need owing to the complex symptoms resulting from metabolic disorder of the wound microenvironment. Although numerous strategies and bioactive hydrogels are developed, an effective and widely used method of chronic wound treatment remains a bottleneck. With the aim to accelerate chronic wound healing, many hydrogel dressings with antioxidant functions have emerged and are proven to accelerate wound healing, especially for chronic wound repair. The new strategy in chronic wound treatment brought by antioxidant hydrogels is of great significance to human health. Here, the application of antioxidant hydrogels in the repair of chronic wounds is discussed systematically, aiming to provide an important theoretical reference for the further breakthrough of chronic wound healing.

Extracellular matrix-mimetic composite hydrogels of cross-linked hyaluronan and fibrillar collagen with tunable properties and ultrastructure

A platform of enzymatically-crosslinked Collagen/Tyramine hyaluronan derivative (Col/HA-Tyr) hydrogels with tunable compositions and gelation conditions was developed to evaluate the impact of the preparation conditions on their physical, chemical and biological properties. At low HA-Tyr content, hydrogels exhibited a fibrillar structure, with lower mechanical properties compared to pure Col hydrogels. At high HA-Tyr and Horse Radish Peroxydase (HRP) content, a microfibrillar network was formed beside the banded Col fibrils and a synergistic effect of the hybrid structure on mechanical properties was observed. These hydrogels were highly resistant against enzymatic degradation while keeping a high degree of hydration. Unlike HA-Tyr hydrogels, encapsulation of human dermal fibroblasts within Col/HA-Tyr hydrogels allowed for high cell viability. These results showed that high HA-Tyr and HRP concentrations are required to positively impact the physical properties of hydrogels while preserving collagen fibrils. Those Col/HA-Tyr hydrogels appear promising for novel tissue engineering applications following a biomimetic approach.

Preparation and characterization of carboxymethyl chitosan/collagen peptide/oxidized konjac composite hydrogel

Medical dressings are used to protect damaged skin from external factors and provide a good healing environment. Hydrogels are aggregates of hydrophilic polymers and water that have a three-dimensional space and can absorb large amounts of water. It has been widely studied in the field of biomedical materials. In this study, we prepared a novel composite hydrogel combined carboxymethyl chitosan, collagen peptide and oxidized konjac, all three materials have been shown to be biocompatible. Then, we set up different hydrogels and tested hydrogels with different proportions. The structures of CMCS (carboxymethyl chitosan)/COP (collagen peptide)/OKGM (oxidized konjac) hydrogels were characterized by IR, NMR, X-ray diffraction and SEM. The effects of hydrogels on the growth of NS-FB and HS-FB cells were studied in vitro. The results of these tests show that the composite hydrogel has excellent mechanical properties and biological activity, and has potential application in wound dressing field.

Wound healing and antimicrobial effect of active secondary metabolites in chitosan-based wound dressings: A review

Wound healing can lead to complex clinical problems, hence finding an efficient approach to enhance the healing process is necessary. An ideal wound dressing should treat wounds at reasonable costs, with minimal inconveniences for the patient. Chitosan is one of the most investigated biopolymers for wound healing applications due to its biocompatibility, biodegradability, non-toxicity, and antimicrobial activity. Moreover, chitosan and its derivative have attracted numerous attentions because of the accelerating wound healing, and easy processability into different forms (gels, foams, membranes, and beads). All these properties make chitosan-based materials particularly versatile and promising for wound dressings. Besides, secondary natural metabolites could potentially act like the antimicrobial and anti-inflammatory agents and accelerate the healing process. This review collected almost all studies regarding natural compounds applications in wound healing by focusing on the chitosan-based bioactive wound dressing systems. An accurate analysis of different chitosan formulations and the influence of bioactive compounds on their wound healing properties are reported.

Priming Dental Pulp Stem Cells from Human Exfoliated Deciduous Teeth with Fibroblast Growth Factor-2 Enhances Mineralization Within Tissue-Engineered Constructs Implanted in Craniofacial Bone Defects

The craniofacial area is prone to trauma or pathologies often resulting in large bone damages. One potential treatment option is the grafting of a tissue-engineered construct seeded with adult mesenchymal stem cells (MSCs). The dental pulp appears as a relevant source of MSCs, as dental pulp stem cells display strong osteogenic properties and are efficient at bone formation and repair. Fibroblast growth factor-2 (FGF-2) and/or hypoxia primings were shown to boost the angiogenesis potential of dental pulp stem cells from human exfoliated deciduous teeth (SHED). Based on these findings, we hypothesized here that these primings would also improve bone formation in the context of craniofacial bone repair. We found that both hypoxic and FGF-2 primings enhanced SHED proliferation and osteogenic differentiation into plastically compressed collagen hydrogels, with a much stronger effect observed with the FGF-2 priming. After implantation in immunodeficient mice, the tissue-engineered constructs seeded with FGF-2 primed SHED mediated faster intramembranous bone formation into critical size calvarial defects than the other groups (no priming and hypoxia priming). The results of this study highlight the interest of FGF-2 priming in tissue engineering for craniofacial bone repair. Stem Cells Translational Medicine 2019;8:844&857.

Topotactic Fibrillogenesis of Freeze-Cast Microridged Collagen Scaffolds for 3D Cell Culture

Type I collagen is the main component of the extracellular matrix (ECM). In vitro, under a narrow window of physicochemical conditions, type I collagen self-assembles to form complex supramolecular architectures reminiscent of those found in native ECM. Presently, a major challenge in collagen-based biomaterials is to couple the delicate collagen fibrillogenesis events with a controlled shaping process in non-denaturating conditions. In this work, an ice-templating approach promoting the structuration of collagen into macroporous monoliths is used. Instead of common solvent removal procedures, a new topotactic conversion approach yielding self-assembled ordered fibrous materials is implemented. These collagen-only, non-cross-linked scaffolds exhibit uncommon mechanical properties in the wet state, with a Young's modulus of 33 ± 12 kPa, an ultimate tensile stress of 33 ± 6 kPa, and a strain at failure of 105 ± 28%. With the help of the ice-patterned microridge features, normal human dermal fibroblasts and C2C12 murine myoblasts successfully migrate and form highly aligned populations within the resulting three-dimensional (3D) collagen scaffolds. These results open a new pathway to the development of new tissue engineering scaffolds ordered across various organization levels from the molecule to the macropore and are of particular interest for biomedical applications where large-scale 3D cell alignment is needed such as for muscular or nerve reconstruction.

Early angiogenesis detected by PET imaging with 64Cu-NODAGA-RGD is predictive of bone critical defect repair

Therapies using stem cells may be applicable to all fields of regenerative medicine, including craniomaxillofacial surgery. Dental pulp stem cells (DPSCs) have demonstrated in vitro and in vivo osteogenic and proangiogenic properties. The aim of the study was to evaluate whether early angiogenesis investigated by nuclear imaging can predict bone formation within a mouse critical bone defect. Two symmetrical calvarial critical-sized defects were created. Defects were left empty or filled with i) DPSC-containing dense collagen scaffold, ii) 5% hypoxia-primed DPSC-containing dense collagen scaffold, iii) acellular dense collagen scaffold, or iv) left empty. Early angiogenesis assessed by PET using ⁶⁴Cu-NODAGA-RGD as a tracer was found to be correlated with bone formation determined by micro-CT within the defects from day 30, and to be correlated to the late calcium apposition observed at day 90 using ¹⁸F-Na PET. These results suggest that nuclear imaging of angiogenesis, a technique applicable in clinical practice, is a promising approach for early prediction of bone grafting outcome, thus potentially allowing to anticipate alternative regenerative strategies. STATEMENT OF SIGNIFICANCE: Bone defects are a major concern in medicine. As life expectancy increases, the number of bone lesions grows, and occurring complications lead to a delay or even lack of consolidation. Therefore, to be able to predict healing or the absence of scarring at early times would be very interesting. This would not "waste time" for the patient. We report here that early nuclear imaging of angiogenesis, using ⁶⁴Cu-NODAGA-RGD as a tracer, associated with nuclear imaging of mineralization, using ¹⁸F-Na as a tracer, is correlated to late bone healing objectivized by classical histology and microtomography. This nuclear imaging represents a promising approach for early prediction of bone grafting outcome in clinical practice, thus potentially allowing to anticipate alternative regenerative strategies.

Decellularized corneal lenticule embedded compressed collagen: toward a suturable collagenous construct for limbal reconstruction

Recently, compressed collagen has attracted much attention as a potential alternative for a limbal epithelial stem cell (LESC) carrier to treat limbal stem cell deficiency (LSCD), in that it can provide mechanically improved collagen fibrillar structures compared to conventional collagen hydrogel. However, its clinical efficacy as an LESC carrier has not yet been studied through in vivo transplantation due to limited mechanical strength that cannot withstand a force induced by surgical suturing and low resistance to enzymatic degradation. This study firstly presents a suturable LESC carrier based on compressed collagen in the form of a biocomposite. The biocomposite was achieved by integrating a decellularized corneal lenticule, which is a decellularized stromal tissue obtained from corneal refractive surgery, inside a compressed collagen to form a sandwich structure. A suture retention test verified that the biocomposite has a much higher suture retention strength (0.56 ± 0.12 N) compared to the compressed collagen (0.02 ± 0.01 N). The biocomposite also exhibited more than 3 times higher resistance to enzymatic degradation, indicating long-term stability after transplantation. In vitro cell culture results revealed that the biocomposite effectively supported the expansion and stratification of the LESCs with expressions of putative stem cell and differentiated corneal epithelial cell markers. Finally, the biocomposite verified its clinical efficacy by stably delivering the LESCs onto an eye of a rabbit model of LSCD and effectively reconstructing the ocular surface.

Self-aggregation of water-dispersible nanocollagen helices

The self-aggregation of water-dispersible native collagen nanofibrils has been investigated to generate hierarchical networks with structural variation from helicity to layering.

Biomacromolecules as carriers in drug delivery and tissue engineering

Natural biomacromolecules have attracted increased attention as carriers in biomedicine in recent years because of their inherent biochemical and biophysical properties including renewability, nontoxicity, biocompatibility, biodegradability, long blood circulation time and targeting ability. Recent advances in our understanding of the biological functions of natural-origin biomacromolecules and the progress in the study of biological drug carriers indicate that such carriers may have advantages over synthetic material-based carriers in terms of half-life, stability, safety and ease of manufacture. In this review, we give a brief introduction to the biochemical properties of the widely used biomacromolecule-based carriers such as albumin, lipoproteins and polysaccharides. Then examples from the clinic and in recent laboratory development are summarized. Finally the current challenges and future prospects of present biological carriers are discussed.

Strategies Developed to Induce, Direct, and Potentiate Bone Healing

Bone exhibits a great ability for endogenous self-healing. Nevertheless, impaired bone regeneration and healing is on the rise due to population aging, increasing incidence of bone trauma and the clinical need for the development of alternative options to autologous bone grafts. Current strategies, including several biomolecules, cellular therapies, biomaterials, and different permutations of these, are now developed to facilitate the vascularization and the engraftment of the constructs, to recreate ultimately a bone tissue with the same properties and characteristics of the native bone. In this review, we browse the existing strategies that are currently developed, using biomolecules, cells and biomaterials, to induce, direct and potentiate bone healing after injury and further discuss the biological processes associated with this repair.

Fabrication of Hybrid Collagen Aerogels Reinforced with Wheat Grass Bioactives as Instructive Scaffolds for Collagen Turnover and Angiogenesis for Wound Healing Applications

The present study illustrates the progress of the wheat grass bioactive-reinforced collagen-based aerogel system as an instructive scaffold for collagen turnover and angiogenesis for wound healing applications. The reinforcement of wheat grass bioactives in collagen resulted in the design and development of aerogels with enhanced physicochemical and biomechanical properties due to the intermolecular interaction between the active growth factors of wheat grass and collagen fibril. Differential scanning calorimetry analysis revealed an enhanced denaturation temperature when compared to those of native collagen aerogels. Fourier transform infrared spectroscopy analysis confirmed that the reinforcement of bioactives in the wheat grass did not affect the structural integrity of the collagen molecule. Additionally, the reinforced biomaterial with a systematic absorptive morphology resulted in a three-dimensional (3D) sponge-like aerogel exhibiting a potent highly oriented 3D structural assembly that showed increased water retention ability and substance permeability that would enable the passage of nutrients and gaseous components for cellular growth. Furthermore, the cumulative effect of the growth factors in wheat grass and the collagen molecule augments the angiogenic ability and collagen production of the aerogel by restoration of the damaged tissue thereby making it a potential 3D wound dressing scaffold. The results were confirmed by in vivo wound healing assays. This study shows the possibility for progress of a biocompatible, biodegradable, and nonadhesive nutraceutical-reinforced collagen aerogel as an instructive scaffold with good antimicrobial properties for collagen turnover and angiogenic response for wound healing applications.

Functionalization of electrospun polymeric wound dressings with antimicrobial peptides

Wound dressings have evolved considerably since ancient times. Modern dressings are now important systems that combine the physical and biochemical properties of natural and synthetic polymers with active compounds that are beneficial to wound healing. Antimicrobial peptides (AMPs) are the most recent addition to these systems. These aim to control the microbial proliferation and colonization of pathogens and to modulate the host's immune response. In the last decade, electrospun wound dressings have been extensively studied and the electrospinning technique recognized as an efficient approach for the production of nanoscale fibrous mats. The control of the electrospinning processing parameters, the selection of the polymer and AMPs, and the definition of the most appropriate AMPs' functionalization method contribute to the successful treatment of acute and chronic wounds. Although the use of electrospinning in wound dressings' production has been previously reviewed, the increased development of AMPs and the establishment of functionalization methods for wound dressings over recent years has increased the need for such research. In the present review, we approach all these subjects and reveal the promising therapeutic potential of wound dressings functionalized with AMPs.