An Additively Manufactured Sample Holder to Measure the Controlled Release of Vancomycin from Collagen Laminates

The controlled release of antibiotics prevents the spread of pathogens and thereby improves healing processes in regenerative medicine. However, high concentrations may interfere with healing processes. It is therefore advantageous to use biodegradable materials for a controlled release. In particular, multilayer materials enable differential release at different surfaces. For this purpose, collagen sheets of different properties can be bonded by photochemical crosslinking. Here, we present the development and application of an easily accessible, additively manufactured sample holder to study the controlled release of vancomycin from modularly assembled collagen laminates in two directions. As proof-of-concept, we show that laminates of collagen sheets covalently linked by rose bengal and green light crosslinking (RGX) can be tightly inserted into the device without leakage from the upper to lower cavity. We used this sample holder to detect the release of vancomycin from symmetrically and asymmetrically loaded two-layer and three-layer collagen laminates into the upper and lower cavity of the sample holder. We show that these collagen laminates are characterized by a collagen type-dependent vancomycin release, enabling the control of antibiotic release profiles as well as the direction of antibiotic release.

Mechanical Characterization of Rose Bengal and Green Light Crosslinked Collagen Scaffolds for Regenerative Medicine

Collagen is one of the most important biomaterials for tissue engineering approaches. Despite its excellent biocompatibility, it shows the non-negligible disadvantage of poor mechanical stability. Photochemical crosslinking with rose bengal and green light (RGX) is an appropriate method to improve this property. The development of collagen laminates is helpful for further adjustment of the mechanical properties as well as the controlled release of incorporated substances. In this study, we investigate the impact of crosslinking and layering of two different collagen scaffolds on the swelling behavior and mechanical behavior in micro tensile tests to obtain information on its wearing comfort (stiffness, strength and ductility). The mechanical stability of the collagen material after degradation due to cell contact is examined using thickness measurements. There is no linear increase or decrease due to layering homologous laminates. Unexpectedly, a decrease in elongation at break, Younǵs modulus and ultimate tensile strength is measured when the untreated monolayer is compared to the crosslinked one. Furthermore we can detect a connection between stability and cell proliferation. The results show that with variation in number and type of layers, collagen scaffolds with tailored mechanical properties can be produced. Such a multi-layered structure enables the release of biomolecules into inner or outer layers for biomedical applications.

Polysaccharide Cryogels Containing β-Cyclodextrin for the Delivery of Cannabidiol

Cannabidiol (CBD) has attracted increasing interest due to its therapeutic potential for treating numerous diseases. However, CBD is very lipophilic and has very unfavorable pharmacokinetics and low bioavailability. Efforts are focused on developing drug delivery systems for enhanced solubilization and therapeutic activity of CBD. Here, we report the preparation of original super-macroporous cryogels from 2-hydroxyethyl cellulose (HEC) and β-cyclodextrin (β-CD) designed for the topical delivery of CBD. The cryogels were synthesized by photochemical crosslinking in a frozen aqueous system, purified, and then loaded with CBD. The effect of HEC/β-CD mass ratio (100:0; 50:50; 40:60 and 20:80) in the reaction mixture on the reaction efficiency, physico-mechanical properties of cryogels, drug release profile, and antineoplastic potential were evaluated in detail. The cryogels showed a bi-phasic release behavior: initial burst release in the first 3 hours followed by slower drug release which can be beneficial in the treatment of cutaneous neoplastic diseases.

Highly Elastic Super-Macroporous Cryogels Fabricated by Thermally Induced Crosslinking of 2-Hydroxyethylcellulose with Citric Acid in Solid State

Biopolymer materials have been considered a “green” alternative to petroleum-based polymeric materials. Biopolymers cannot completely replace synthetic polymers, but their application should be extended as much as possible, exploiting the benefits of their low toxicity and biodegradability. This contribution describes a novel strategy for the synthesis of super-macroporous 2-hydroxyethylcellulose (HEC) cryogels. The method involves cryogenic treatment of an aqueous solution of HEC and citric acid (CA), freeze drying, and thermally induced crosslinking of HEC macrochains by CA in a solid state. The effect of reaction temperature (70–180 °C) and CA concentration (5–20 mass % to HEC) on the reaction efficacy and physico-mechanical properties of materials was investigated. Highly elastic cryogels were fabricated, with crosslinking carried out at ≥ 100 °C. The storage modulus of the newly obtained HEC cryogels was ca. 20 times higher than the modulus of pure HEC cryogels prepared by photochemical crosslinking. HEC cryogels possess an open porous structure, as confirmed by scanning electron microscopy (SEM), and uptake a relatively large amount of water. The swelling degree varied between 17 and 40, depending on the experimental conditions. The degradability of HEC cryogels was demonstrated by acid hydrolysis experiments.

Light and Hydrogels: A New Generation of Antimicrobial Materials

Nosocomial diseases are becoming a scourge in hospitals worldwide, and new multidrug-resistant microorganisms are appearing at the forefront, significantly increasing the number of deaths. Innovative solutions must emerge to prevent the imminent health crisis risk, and antibacterial hydrogels are one of them. In addition to this, for the past ten years, photochemistry has become an appealing green process attracting continuous attention from scientists in the scope of sustainable development, as it exhibits many advantages over other methods used in polymer chemistry. Therefore, the combination of antimicrobial hydrogels and light has become a matter of course to design innovative antimicrobial materials. In the present review, we focus on the use of photochemistry to highlight two categories of hydrogels: (a) antibacterial hydrogels synthesized via a free-radical photochemical crosslinking process and (b) chemical hydrogels with light-triggered antibacterial properties. Numerous examples of these new types of hydrogels are described, and some notions of photochemistry are introduced.

Development of nanostructured bioplastic material for wound healing

The development of new biomaterials whose characteristics are as close as possible to the properties of living human tissues is one of the most promising areas of regenerative medicine. This work aimed at creating a bioplastic material based on collagen, elastin and hyaluronic acid and studying its structure and properties to assess the prospects for further use in clinical practice. Bioplastic material was obtained by mixing collagen, hyaluronic acid and elastin in predetermined proportions with distilled water. We treated the material with photochemical crosslinking to stabilize biofilm in a liquid medium and form a nanostructured scaffold. A commercial human skin fibroblast cell culture was used to assess the biomaterial cytotoxicity and biocompatibility. The visualization and studies of the biomaterial structure were performed using light and scanning electron microscopy. It has been shown that the obtained biomaterial is characterized by high resilience; it has also a high porosity. The co-culturing of the bioplastic material and human fibroblasts did not reveal any of its cytotoxic effects on cells in culture. It was shown that the biomaterial samples could maintain physical properties in the culture medium for more than 10 days, while the destruction of the matrix was observed 3–4 weeks after the beginning of incubation. Thus, the created biomaterial can be used on damaged skin areas due to its physical properties and structure. The use of the developed biomaterial provides effective conditions for good cell proliferation, which allows us to consider it as a promising wound cover for use in clinical practice.

Development of nanostructured bioplastic material for wound healing

The development of new biomaterials whose characteristics are as close as possible to the properties of living human tissues is one of the most promising areas of regenerative medicine. This work aimed at creating a bioplastic material based on collagen, elastin and hyaluronic acid and studying its structure and properties to assess the prospects for further use in clinical practice. Bioplastic material was obtained by mixing collagen, hyaluronic acid and elastin in predetermined proportions with distilled water. We treated the material with photochemical crosslinking to stabilize biofilm in a liquid medium and form a nanostructured scaffold. A commercial human skin fibroblast cell culture was used to assess the biomaterial cytotoxicity and biocompatibility. The visualization and studies of the biomaterial structure were performed using light and scanning electron microscopy. It has been shown that the obtained biomaterial is characterized by high resilience; it has also a high porosity. The co-culturing of the bioplastic material and human fibroblasts did not reveal any of its cytotoxic effects on cells in culture. It was shown that the biomaterial samples could maintain physical properties in the culture medium for more than 10 days, while the destruction of the matrix was observed 3–4 weeks after the beginning of incubation. Thus, the created biomaterial can be used on damaged skin areas due to its physical properties and structure. The use of the developed biomaterial provides effective conditions for good cell proliferation, which allows us to consider it as a promising wound cover for use in clinical practice.

Robust Topographical Micro-Patterning of Nanofibrillar Collagen Gel by In Situ Photochemical Crosslinking-Assisted Collagen Embossing

The topographical micro-patterning of nanofibrillar collagen gels is promising for the fabrication of biofunctional constructs mimicking topographical cell microenvironments of in vivo extracellular matrices. Nevertheless, obtaining structurally robust collagen micro-patterns through this technique is still a challenging issue. Here, we report a novel in situ photochemical crosslinking-assisted collagen embossing (IPC-CE) process as an integrative fabrication technique based on collagen compression-based embossing and UV–riboflavin crosslinking. The IPC-CE process using a micro-patterned polydimethylsiloxane (PDMS) master mold enables the compaction of collagen nanofibrils into micro-cavities of the mold and the simultaneous occurrence of riboflavin-mediated photochemical reactions among the nanofibrils, resulting in a robust micro-patterned collagen construct. The micro-patterned collagen construct fabricated through the IPC-CE showed a remarkable mechanical resistivity against rehydration and manual handling, which could not be achieved through the conventional collagen compression-based embossing alone. Micro-patterns of various sizes (minimum feature size <10 μm) and shapes could be obtained by controlling the compressive pressure (115 kPa) and the UV dose (3.00 J/cm2) applied during the process. NIH 3T3 cell culture on the micro-patterned collagen construct finally demonstrated its practical applicability in biological applications, showing a notable effect of anisotropic topography on cells in comparison with the conventional construct.