Nowadays, tissue engineering is described as an interdisciplinary field that combines engineering principles and life sciences to generate implantable devices to repair, restore and/or improve functions of injured tissues. Such devices are designed to induce the interaction and integration of tissue and cells within the implantable matrices and are manufactured to meet the appropriate physical, mechanical and physiological local demands. Biodegradable constructs based on polymeric fibers are desirable for tissue engineering due to their large surface area, interconnectivity, open pore structure, and controlled mechanical strength. Additionally, biodegradable constructs are also very sought-out for biomolecule delivery systems with a target-directed action. In the present review, we explore the properties of some of the most common biodegradable polymers used in tissue engineering applications and biomolecule delivery systems and highlight their most important uses.

New approaches to deal with the growing concern associated with antibiotic-resistant bacteria are emerging daily. Essential oils (EOs) are natural antimicrobial substances with great potential to mitigate this situation. However, their volatile nature, in their liquid-free form, has restricted their generalized application in biomedicine. Here, we propose the use of cellulose acetate (CA)/polycaprolactone (PCL) wet-spun fibers as potential delivery platforms of selected EOs to fight infections caused by Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Twenty EOs were selected and screened for their minimal inhibitory concentration (MIC), using the antibiotic ampicillin as positive control. The cinnamon leaf oil (CLO), cajeput oil (CJO), and the clove oil (CO) were the most effective EOs, against the Gram-positive (MIC < 22.38 mg/mL) and the Gram-negative (MIC < 11.19 mg/mL) bacteria. Uniform microfibers were successfully wet-spun from CA/PCL with an averaged diameter of 53.9 ± 4.5 µm, and then modified by immersion with CLO, CJO and CO at 2 × MIC value. EOs incorporation was confirmed by UV-visible spectroscopy, Fourier-transformed infrared spectroscopy, and thermal gravimetric analysis. However, while microfibers contained ampicillin at MIC (control) after the 72 h modification, the CLO, CO and CJO-loaded fibers registered ≈ 14%, 66%, and 76% of their MIC value, respectively. Data showed that even at small amounts the EO-modified microfibers were effective against the tested bacteria, both by killing bacteria more quickly or by disrupting more easily their cytoplasmic membrane than ampicillin. Considering the amount immobilized, CLO-modified fibers were deemed the most effective from the EOs group. These results indicate that CA/PCL microfibers loaded with EOs can be easily produced with increased antibacterial action, envisioning their use as scaffolding materials for the treatment of infections.

Wet-spinning is a non-solvent induced phase inversion technique that allows the production of continuous polymeric microfibers, with a uniform morphology, based on the principle of precipitation. It allows the production of 3D fibrous constructs with an intricated architecture that facilitates cell infiltration, something that is very limited in electrospun nanofibrous mats, thus increasing its interest in biomedicine. Wet-spun scaffolds are also more easily processed and can be loaded with a variety of biomolecules of interest. Antimicrobial agents that display a broad spectrum of activity against bacteria, fungi and viruses have been combined with such constructs demonstrating great potential to fight infections. In the present work, we explore the use of wet-spinning to process both natural and synthetic biodegradable polymers in the form of microfibers, and the necessary processes to modify their surface to increase their antimicrobial profile. The synergistic potential of specialized biomolecules within wet-spun fibrous architectures are also highlighted.

To tackle one of the biggest global health problems, the resistance of microorganisms to antibiotics, a collective effort in the search for more effective agents against bacteria was required. Peptides with antimicrobial activity have been raising much attention as a promising alternative for antibiotics. Peptaibols, for instance, are a family of antimicrobial peptides (AMPs) with great biomedical potential, in which the Peptaibolin can be highlighted. This peptide has gained relevance due to its small amino acids content, only four, and its acetyl group and a phenylalaninol residue (Phol) at the N-terminal and C-terminal, respectively. Here, we report the synthesis of Peptaibolin through Solid Phase Peptide Synthesis assisted by Microwave heating (MW-SPPS) in a pre-loaded Phe-Wang resin. Starting from a loading of 0.51 mmol/g, two syntheses were made, using two different combinations of coupling reagents. The best option was DIC/Oxima, achieving a yield of 50.0%. Proton Nuclear Magnetic Resonance (¹H-NMR) studies confirmed the peptide structure, while High Performance Liquid Chromatography (HPLC) verified the peptide purity. The peptide solubility was examined against several combinations of solvents. Peptaibolin was not soluble in water, only in organic solvents or in the combination of both. Antimicrobial testing was conducted using Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa. Minimum inhibitory concentration studies demonstrated the resistance of bacteria to the peptide action and the peptide instability in bacterial growth conditions.

Essential oils (EOs), which are complex biomolecules composed of volatile compounds, have emerged as a new strategy to deal with bacterial infections and as a valid alternative to synthetic drugs. Here, we report the production and modification of wet-spun microfibers made of cellulose acetate (CA) and polycaprolactone (PCL) with the EOs cinnamon leaf oil (CLO), cajeput oil (CJO), and clove oil (CO). These were selected from a group of 20 EOs according to their minimal inhibitory concentration (MIC) against Staphylococcus aureus (<22.4 mg/mL) and Escherichia coli (<11.2 mg/mL) bacteria. Microfibers were produced by wet-spinning at an extrusion rate of 0.5 mL/h directly into an ethanol coagulation bath. EOs loading was accomplished by immersion in ethanol solutions containing the EOs at 2xMIC. Incorporation was confirmed by UV-Visible spectroscopy and Fourier-transformed infrared spectroscopy. After 72 h of incubation, microfibers contained 14%, 66% and 76% of the MIC values of CLO, CO and CJO, respectively. Unloaded and loaded microfibers were characterized as uniform and homogeneous; no significant differences were detected. EO-modified microfibers were effective against the tested bacteria. Considering the amount immobilized, CLO-containing fibers were deemed the most effective from the group, suggesting a superior affinity of the EOs active groups towards the CA/PCL matrix. These results indicate that CA/PCL microfibers loaded with EOs have potential for biomedical application in which infection control is the target.