Copper-Cystine Biohybrid-Embedded Nanofiber Aerogels Show Antibacterial and Angiogenic Properties.

Copper-cystine-based high aspect ratio structures (CuHARS) possess exceptional physical and chemical properties and exhibit remarkable biodegradability in human physiological conditions. Extensive testing has confirmed the biocompatibility and biodegradability of CuHARS under diverse biological conditions, making them a viable source of essential Cu2+. These ions are vital for catalyzing the production of nitric oxide (NO) from the decomposition of S-nitrosothiols (RSNOs) found in human blood. The ability of CuHARS to act as a Cu2+ donor under specific concentrations has been demonstrated in this study, resulting in the generation of elevated levels of NO. Consequently, this dual function makes CuHARS effective as both a bactericidal agent and a promoter of angiogenesis. In vitro experiments have shown that CuHARS actively promotes the migration and formation of complete lumens by redirecting microvascular endothelial cells. To maximize the benefits of CuHARS, they have been incorporated into biomimetic electrospun poly(ε-caprolactone)/gelatin nanofiber aerogels. Through the regulated release of Cu2+ and NO production, these channeled aerogels not only provide antibacterial support but also promote angiogenesis. Taken together, the inclusion of CuHARS in biomimetic scaffolds could hold great promise in revolutionizing tissue regeneration and wound healing.

Hydrophobic composite foams based on nanocellulose-sepiolite for oil sorption applications.

TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl)-oxidized cellulose nanofibers (CNF) were assembled to fibrous clay sepiolite (SEP) by means of a high shear homogenizer and an ultrasound treatment followed by lyophilization using three different methods: normal freezing, directional freezing, and a sequential combination of both methods. Methyltrimethoxysilane (MTMS) was grafted to the foam surface by the vapor deposition method to introduce hydrophobicity to the resulting materials. Both the SEP addition (for the normal and directional freezing methods) and the refreezing preparation procedure enhanced the compressive strength of the foams, showing compressive moduli in the range from 28 to 103 kPa for foams loaded with 20% w/w sepiolite. Mercury intrusion porosimetry shows that the average pore diameters were in the range of 30-45 µm depending on the freezing method. This large porosity leads to materials with very low apparent density, around 6 mg/cm3, and very high porosity >99.5%. In addition, water contact angle measurement and Fourier-transform infrared spectroscopy (FTIR) were applied to confirm the foam hydrophobicity, which is suitable for use as an oil sorbent. The sorption ability of these composite foams has been tested using olive and motor oils as models of organophilic liquid adsorbates, observing a maximum sorption capacity of 138 and 90 g/g, respectively.

Alginate bionanocomposite films containing sepiolite modified with polyphenols from myrtle berries extract.

Alginate nanocomposite films incorporating sepiolite (Sep) modified with myrtle berries extract (MBE) rich in polyphenols were prepared by solution casting method. The effects of different extract concentrations on the film properties were determined by measuring physicochemical, mechanical and antioxidant properties of the films. Fourier transform infrared (FTIR) spectra indicated that strong interactions between the polyphenols present in the MBE and sepiolite were involved in the films. The results suggested that incorporation of Sep-MBE hybrids into the films improved elongation at break, tensile strength, water vapor and UV barrier properties compared to the control film. The antioxidant activity of the films was significantly improved and raised with increasing content of MBE. The release kinetics results of MBE polyphenols from the active films into alcoholic food simulant indicated that the addition of Sep-MBE hybrids to alginate film is able to slow the release of MBE polyphenols. This study revealed the benefits of incorporation of Sep-MBE hybrids into the alginate films and their potential application as active packaging films or coating material.

Cellulose-based biomaterials integrated with copper-cystine hybrid structures as catalysts for nitric oxide generation.

Bionanocomposite materials were developed from the assembly of polymer-coated copper-cystine high-aspect ratio structures (CuHARS) and cellulose fibers. The coating of the metal-organic materials with polyallylamine hydrochloride (PAH) allows their covalent linkage to TEMPO-oxidized cellulose by means of EDC/NHS. The resulting materials can be processed as films or macroporous foams by solvent casting and lyophilization, respectively. The films show good mechanical behavior with Young's moduli around 1.5 GPa as well as resistance in water, while the obtained foams show an open network of interconnected macropores with average diameters around 130 µm, depending on the concentration of the initial suspension, and compression modulus values around 450 kPa, similar to other reported freeze-dried nanocellulose-based aerogels. Based on these characteristics, the cellulose/PAH-CuHARS composites are promising for potential biomedical applications as implants or wound dressing materials. They have proved to be effective in the decomposition of low molecular weight S-nitrosothiols (RSNOs), similar to those existing in blood, releasing nitric oxide (NO). This effect is attributed to the presence of copper in the crystalline structure of the CuHARS building unit, which can be gradually released in the presence of redox species like ascorbic acid, typically found in blood. The resulting biomaterials can offer the interesting properties associated with NO, like antimicrobial activity as preliminary tests showed here with Escherichia coli and Staphylococcus epidermidis. In the presence of physiological concentration of RSNOs the amount of generated NO (around 360 nM) is not enough to show bactericidal effect on the studied bacteria, but it could provide other properties inherent to NO even at low concentration in the nM range like anti-inflammatory and anti-thrombotic effects. The cytotoxic effect recorded of the films on rat brain endothelial cells (BMVECs) is least significant and proves them to be friendly enough for further biological studies.

Integration of a Copper-Containing Biohybrid (CuHARS) with Cellulose for Subsequent Degradation and Biomedical Control.

We previously described the novel synthesis of a copper high-aspect ratio structure (CuHARS) biohybrid material using cystine. While extremely stable in water, CuHARS is completely (but slowly) degradable in cellular media. Here, integration of the CuHARS into cellulose matrices was carried out to provide added control for CuHARS degradation. Synthesized CuHARS was concentrated by centrifugation and then dried. The weighed mass was re-suspended in water. CuHARS was stable in water for months without degradation. In contrast, 25 μg/mL of the CuHARS in complete cell culture media was completely degraded (slowly) in 18 days under physiological conditions. Stable integration of CuHARS into cellulose matrices was achieved through assembly by mixing cellulose micro- and nano-fibers and CuHARS in an aqueous (pulp mixture) phase, followed by drying. Additional materials were integrated to make the hybrids magnetically susceptible. The cellulose-CuHARS composite films could be transferred, weighed, and cut into usable pieces; they maintained their form after rehydration in water for at least 7 days and were compatible with cell culture studies using brain tumor (glioma) cells. These studies demonstrate utility of a CuHARS-cellulose biohybrid for applied applications including: (1) a platform for biomedical tracking and (2) integration into a 2D/3D matrix using natural products (cellulose).

Gelation under dynamic conditions: a strategy for in vitro cell ordering.

Ordered gelation under spin-coating conditions, as reported here, is a suitable method to order cells in biogels. Cell ordering is of great importance for functional repair of central nervous system (CNS) injuries, because therapies must include strategies to bridge chystic gaps and facilitate axon growth towards its target. Organized biocompatible and biodegradable substrates may be used for this purpose, to supply trophic support and provide directional cues for neuronal process outgrowth. Atomic force microscopy (AFM) and low temperature scanning electron microscopy (LTSEM), confirmed that fibrils in kappa-carrageenan/chitosan and fibrin hydrogels prepared under spin-coating conditions, were longitudinally arranged. The cell model was conveniently tested using rat C6 glioma cells. C6 cells were distributed regularly in fibrin gels formed under centrifugal force. The ability of ordered fibrin scaffolds to promote uniform distribution of transplanted cells, was confirmed by fluorescence microscopy.