Printing in situ tissue sealant with visible-light-crosslinked porous hydrogel

Effect of Encapsulation of Lactobacillus casei in Alginate-Tapioca Flour Microspheres Coated with Different Biopolymers on the Viability of Probiotic Bacteria

To realize the health benefits of probiotic bacteria, they must withstand processing and storage conditions and remain viable after use. The encapsulation of these probiotics in the form of microspheres containing tapioca flour as a prebiotic and vehicle component in their structure or shell affords symbiotic effects that improve the survival of probiotics under unfavorable conditions. Microencapsulation is one such method that has proven to be effective in protecting probiotics from adverse conditions while maintaining their viability and functionality. The aim of the work was to obtain high-quality microspheres that can act as carriers of Lactobacillus casei bacteria and to assess the impact of encapsulation on the viability of probiotic microorganisms in alginate microspheres enriched with a prebiotic (tapioca flour) and additionally coated with hyaluronic acid, chitosan, or gelatin. The influence of the composition of microparticles on the physicochemical properties and the viability of probiotic bacteria during storage was examined. The optimal composition of microspheres was selected using the design of experiments using statistical methods. Subsequently, the size, morphology, and cross-section of the obtained microspheres, as well as the effectiveness of the microsphere coating with biopolymers, were analyzed. The chemical structure of the microspheres was identified by using Fourier-transform infrared spectrophotometry. Raman spectroscopy was used to confirm the success of coating the microspheres with the selected biopolymers. The obtained results showed that the addition of tapioca flour had a positive effect on the surface modification of the microspheres, causing the porous structure of the alginate microparticles to become smaller and more sealed. Moreover, the addition of prebiotic and biopolymer coatings of the microspheres, particularly using hyaluronic acid and chitosan, significantly improved the survival and viability of the probiotic strain during long-term storage. The highest survival rate of the probiotic strain was recorded for alginate-tapioca flour microspheres coated with hyaluronic acid, at 5.48 log CFU g-1. The survival rate of L. casei in that vehicle system was 89% after storage for 30 days of storage.

4D printing of biological macromolecules employing handheld bioprinters for in situ wound healing applications

In situ bioprinting may be preferred over standard in vitro bioprinting in specific cases when de novo tissues are to be created directly on the appropriate anatomical region in the live organism, employing the body as a bioreactor. So far, few efforts have been made to create in situ tissues that can be safely halted and immobilized during printing in preclinical live animals. However, the technique has to be improved significantly in order to manufacture complex tissues in situ, which may be attainable in the future thanks to multidisciplinary advances in tissue engineering. Thanks to the biological macromolecules, natural and synthetic hydrogels and polymers are among the most used biomaterials in in situ bioprinting procedure. Bioprinters, which encounter multiple challenges, including cross-linking the printed structure, adjusting the rheology parameters, and printing various constructs. The introduction of handheld 3D and 4D bioprinters might potentially overcome the difficulties and problems associated with using traditional bioprinters. Studies showed that this technique could be efficient in wound healing and skin tissue regeneration. This study aims to analyze the benefits and difficulties associated with materials in situ 4D printing via handheld bioprinters.

Biofabrication of Cellulose-based Hydrogels for Advanced Wound Healing: A Special Emphasis on 3D Bioprinting

Even with the current advancements in wound management, addressing most skin injuries and wounds continues to pose a significant obstacle for the healthcare industry. As a result, researchers are now focusing on creating innovative materials utilizing cellulose and its derivatives. Cellulose, the most abundant biopolymer in nature, has unique properties that make it a promising material for wound healing, such as biocompatibility, tunable physiochemical characteristics, accessibility, and low cost. 3D bioprinting technology has enabled the production of cellulose-based wound dressings with complex structures that mimic the extracellular matrix. The inclusion of bioactive molecules such as growth factors offers the ability to aid in promoting wound healing, while cellulose creates an ideal environment for controlled release of these biomolecules and moisture retention. The use of 3D bioprinted cellulose-based wound dressings has potential benefits for managing chronic wounds, burns, and painful wounds by promoting wound healing and reducing the risk of infection. This review provides an up-to-date summary of cellulose-based dressings manufactured by 3D bioprinting techniques by looking into wound healing biology, biofabrication methods, cellulose derivatives, and the existing cellulose bioinks targeted toward wound healing.

Recent advances in 3D printed cellulose-based wound dressings: A review on in vitro and in vivo achievements

Chronic wounds, especially diabetic ulcers, pose a significant challenge in regenerative medicine. Cellulose derivatives offer remarkable wound management properties, such as effective absorption and retention of wound exudates, maintaining an optimal moisture environment crucial for successful chronic wound regeneration. However, conventional dressings have limited efficacy in managing and healing these types of skin lesions, driving scientists to explore innovative approaches. The emergence of 3D printing has enabled personalized dressings that meet individual patient needs, improving the healing process and patient comfort. Cellulose derivatives meet the demanding requirements for biocompatibility, printability, and biofabrication necessary for 3D printing of biologically active scaffolds. However, the potential applications of nanocellulose and cellulose derivative-based inks for wound regeneration remain largely unexplored. Thus, this review provides a comprehensive overview of recent advancements in cellulose-based inks for 3D printing of personalized wound dressings. The composition and biofabrication approaches of cellulose-based wound dressings are thoroughly discussed, including the functionalization with bioactive molecules and antibiotics for improved wound regeneration. Similarly, the in vitro and in vivo performance of these dressings is extensively examined. In summary, this review aims to highlight the exceptional advantages and diverse applications of 3D printed cellulose-based dressings in personalized wound care.

Bioprinting the future using light: A review on photocrosslinking reactions, photoreactive groups, and photoinitiators

Light-based bioprinting is a type of additive manufacturing technologies that uses light to control the formation of biomaterials, tissues, and organs. It has the potential to revolutionize the adopted approach in tissue engineering and regenerative medicine by allowing the creation of functional tissues and organs with high precision and control. The main chemical components of light-based bioprinting are activated polymers and photoinitiators. The general photocrosslinking mechanisms of biomaterials are described, along with the selection of polymers, functional group modifications, and photoinitiators. For activated polymers, acrylate polymers are ubiquitous but are made of cytotoxic reagents. A milder option that exists is based on norbornyl groups which are biocompatible and can be used in self-polymerization or with thiol reagents for more precision. Polyethylene-glycol and gelatin activated with both methods can have high cell viability rates. Photoinitiators can be divided into types I and II. The best performances for type I photoinitiators are produced under ultraviolet light. Most alternatives for visible-light-driven photoinitiators were of type II, and changing the co-initiator along the main reagent can fine-tune the process. This field is still underexplored and a vast room for improvements still exist, which can open the way for cheaper complexes to be developed. The progress, advantages, and shortcomings of light-based bioprinting are highlighted in this review, with special emphasis on developments and future trends of activated polymers and photoinitiators.

Green Chemistry for Crosslinking Biopolymers: Recent Advances in Riboflavin-Mediated Photochemistry

Riboflavin (RF), which is also known as vitamin B2, is a water-soluble vitamin. RF is a nontoxic and biocompatible natural substance. It absorbs light (at wavelengths of 380 and 450 nm) in the presence of oxygen to form reactive singlet oxygen (¹O₂). The generated singlet oxygen acts as a photoinitiator to induce the oxidation of biomolecules, such as amino acids, proteins, and nucleotides, or to initiate chemical reactions, such as the thiol-ene reaction and crosslinking of tyramine and furfuryl groups. In this review, we focus on the chemical mechanism and utilization of the photochemistry of RF, such as protein crosslinking and hydrogel formation. Currently, the crosslinking method using RF as a photoinitiator is actively employed in ophthalmic clinics. However, a significant broadening is expected in its range of applications, such as in tissue engineering and drug delivery.

Bio-macromolecular design roadmap towards tough bioadhesives

Emerging sutureless wound-closure techniques have led to paradigm shifts in wound management. State-of-the-art biomaterials offer biocompatible and biodegradable platforms enabling high cohesion (toughness) and adhesion for rapid bleeding control as well as robust attachment of implantable devices. Tough bioadhesion stems from the synergistic contributions of cohesive and adhesive interactions. This Review provides a biomacromolecular design roadmap for the development of tough adhesive surgical sealants. We discuss a library of materials and methods to introduce toughness and adhesion to biomaterials. Intrinsically tough and elastic polymers are leveraged primarily by introducing strong but dynamic inter- and intramolecular interactions either through polymer chain design or using crosslink regulating additives. In addition, many efforts have been made to promote underwater adhesion via covalent/noncovalent bonds, or through micro/macro-interlock mechanisms at the tissue interfaces. The materials settings and functional additives for this purpose and the related characterization methods are reviewed. Measurements and reporting needs for fair comparisons of different materials and their properties are discussed. Finally, future directions and further research opportunities for developing tough bioadhesive surgical sealants are highlighted.

Contemporary Approach to the Porosity of Dental Materials and Methods of Its Measurement

Porosity is an important parameter for characterizing the microstructure of solids that corresponds to the volume of the void space, which may contain fluid or air, over the total volume of the material. Many materials of natural and technically manufactured origin have a large number of voids in their internal structure, relatively small in size, compared to the characteristic dimensions of the body itself. Thus, porosity is an important feature of industrial materials, but also of biological ones. The porous structure affects a number of material properties, such as sorption capacity, as well as mechanical, thermal, and electrical properties. Porosity of materials is an important factor in research on biomaterials. The most popular materials used to rebuild damaged tooth tissues are composites and ceramics, whilst titanium alloys are used in the production of implants that replace the tooth root. Research indicates that the most comprehensive approach to examining such materials should involve an analysis using several complementary methods covering the widest possible range of pore sizes. In addition to the constantly observed increase in the resolution capabilities of devices, the development of computational models and algorithms improving the quality of the measurement signal remains a big challenge.

Photopolymerized Porous Hydrogels

Hydrogels are polymeric networks highly swollen with water. Because of their versatility and properties mimicking biological tissues, they are very interesting for biomedical applications. In this aim, the control of porosity is of crucial importance since it governs the transport properties and influences the fate of cells cultured onto or into the hydrogels. Among the techniques allowing for the elaboration of hydrogels, photopolymerization or photo-cross-linking are probably the most powerful and versatile synthetic routes. This Review aims at giving an overview of the literature dealing with photopolymerized hydrogels for which the generation or characterization of porosity is studied. First, the materials (polymers and photoinitiating systems) used for synthesizing hydrogels are presented. The different ways for generating porosity in the photopolymerized hydrogels are explained, and the characterization techniques allowing adequate study of the porosity are presented. Finally, some applications in the field of controlled release and tissue engineering are reviewed.

Platelet-Derived Growth Factor Stimulated Migration of Bone Marrow Mesenchymal Stem Cells into an Injectable Gelatin-Hydroxyphenyl Propionic Acid Matrix

Bone marrow mesenchymal stem cells (bMSCs) are responsible in the repair of injured tissue through differentiation into multiple cell types and secretion of paracrine factors, and thus have a broad application profile in tissue engineering/regenerative medicine, especially for the musculoskeletal system. The lesion due to injury or disease may be a closed irregular-shaped cavity deep within tissue necessitating an injectable biomaterial permissive of host (endogenous) cell migration, proliferation and differentiation. Gelatin-hydroxyphenyl propionic acid (Gtn-HPA) is a natural biopolymer hydrogel which is covalently cross-linked by horseradish peroxidase (HRP) and hydrogen peroxide (H₂O₂) in situ and can be delivered to the lesion by needle injection. Growth factors and cytokines can be directly incorporated into the gel or into nano- and micro-particles, which can be employed for sustained release of biomolecules while maintaining their bioactivity. In this study, we selected polyelectrolyte complex nanoparticles (PCNs) prepared with dextran sulfate and chitosan as the carrier for platelet-derived growth factor (PDGF)-BB and stromal cell-derived factor (SDF)-1α, which have been tested effectively in recruiting stem cells. Our in vitro results showed a high degree of viability of bMSCs through the process of Gtn-HPA covalent cross-linking gelation. The Gtn-HPA matrix was highly permissive of bMSC migration, proliferation, and differentiation. PDGF-BB (20 ng/mL) directly incorporated into the gel and, alternatively, released from PCNs stimulated bMSC migration and proliferation. There were only small differences in the results for the direct incorporation of PDGF into the gel compared with its release from PCNs, and for increased doses of the growth factor (200 ng/mL and 2 µg/mL). In contrast, SDF-1α elicited an increase in migration and proliferation only when released from PCNs; its effect on migration was notably less than PDGF-BB. The in vitro results demonstrate that PDGF-BB substantially increases migration of bMSCs into Gtn-HPA and their proliferation in the gel, and that these benefits can be derived from incorporation of a relatively low dose of the growth factor directly into the gel. These findings commend the use of Gtn-HPA/PDGF-BB as an injectable therapeutic agent to treat defects in musculoskeletal tissues.

Nanoemulsion Gel Formulation Optimization for Burn Wounds: Analysis of Rheological and Sensory Properties

Background: Despite the variety of treatment methods for wounds and scars after burns, there are still few effective preparations that can be used in a non-invasive therapy. Recent years have seen significant development of nanomedicine and nanotechnology in the treatment of infection in burn wounds. Proposal: The aim of this work was to develop a formula of a nanoemulsion gel for skin regeneration after burns, and to compare its rheological and sensory properties, as well as the effectiveness of post-burn skin regeneration with preparations available on the market. Methods: At the first stage of studies the composition and parameters of the preparation of sea buckthorn oil-based O/W (oil-in-water) nanoemulsion containing hyaluronic acid and aloe vera gel, as the active ingredients were optimized. Then, the nanoemulsion was added to the gel matrix composed of carbomer (1%) and water which resulted in receiving nanoemulgel. The physicochemical parameters of the obtained samples were characterized by means of dynamic light scattering method and scanning electron microscope. Rheological, sensory and influence on skin condition analysis was conducted for selected market products and developed nanoemulgel. Results: Nanoemulsion gel (d = 211 ± 1.4 nm, polydispersity index (PDI) = 0.205 ± 0.01) was characterized by semi-solid, non-sticky consistency, porous structure, law viscosity, good “primary” and “secondary” skin feelings and pleasant sensorical properties. It improves the condition of burned skin by creating a protective layer on the skin and increasing the hydration level. Conclusion: Due to the fact that the obtained nanoemulsion gel combines the advantages of an emulsion and a gel formulation, it can be a promising alternative to medical cosmetics available on the market, as a form of formulation used in skin care after burns.

Eprinomectin nanoemulgel for transdermal delivery against endoparasites and ectoparasites: preparation, in vitro and in vivo evaluation

Nanoemulgels are composed of O/W nanoemulsion and hydrogels and are considered as ideal carriers for the transdermal drug delivery because these have high affinity to load hydrophobic drugs. The stable formulation of eprinomectin (EPR) is very challenging because of it is high hydrophobic nature. In this work, we have prepared EPR loaded nanoemulgel for the treatment of endo- and ectoparasites. The surface morphology of optimized formulations was characterized by scanning electron microscopy. Additionally, skin permeability and irritation tests were conducted for in vitro safety and in vivo skin retention and pearmeation test of EPR nanoemulgel were conducted for efficacy study. Obtained results indicated that the optimized formulation had good shear-thinning behavior, bioadhesiveness properties, and are nanosized droplets with porous internal structure, which are required for topical application. Furthermore, this formulation has showed good skin permeability in comparison to suspension and has no skin irritating property. Overall, the obtained results proved that nanoemulgel is a promising carrier for transdermal drug delivery and EPR nanoemulgel is a promising formulation for the treatment of endo- and ectoparasites.

Balancing the thickness of sensitizing and inert layers in neodymium-sensitized tetralayer nanoconstructs for optimal ultraviolet upconversion and near-infrared cross-linked hydrogel tissue sealants

Balancing the thickness of sensitizing and inert layers in neodymium-sensitized tetralayer nanoconstructs for optimal ultraviolet upconversion.

Recent advances in the development of nature-derived photocrosslinkable biomaterials for 3D printing in tissue engineering

BACKGROUND

In recent years, three-dimensional (3D) printing has begun to be widely used in tissue engineering. Natural biomaterials have been employed to overcome the limitations of synthetic polymers. However, their low mechanical strength and poor printability are major disadvantages. Photocrosslinking is the most promising fabrication strategy because it is non-invasive and easy to control light intensity and exposure. In this article, developments of photocrosslinkable natural biomaterials in the field of 3D printing are reviewed.

MAIN BODY

Photocrosslinkable biomaterials can be broadly classified into materials that use ultraviolet (UV) and visible lights. Many natural biomaterials such as gelatin, hydroxyapatite, silk fibroin, and pectin have been modified through acrylation, crosslinked by 365 nm UV light, and 3D printed. Riboflavin could also be used to crosslink and print collagen or decellularized extracellular matrix (dECM). In the case of silk-like aneroin and modified gelatin, crosslinking is possible by forming a dityrosine bond using 452 nm visible light.

CONCLUSION

Despite the tremendous researches on the developments of photocrosslinkable 3D printing natural biomaterials, further efforts are necessary to develop source biomaterials with excellent biological functions and sufficient mechanical integrity.