Frog nest foams exhibit pharmaceutical foam-like properties.

Foams have frequently been used as systems for the delivery of cosmetic and therapeutic molecules; however, there is high variability in the foamability and long-term stability of synthetic foams. The development of pharmaceutical foams that exhibit desirable foaming properties, delivering appropriate amounts of the active pharmaceutical ingredient (API) and that have excellent biocompatibility is of great interest. The production of stable foams is rare in the natural world; however, certain species of frogs have adopted foam production as a means of providing a protective environment for their eggs and larvae from predators and parasites, to prevent desiccation, to control gaseous exchange, to buffer temperature extremes, and to reduce UV damage. These foams show great stability (up to 10 days in tropical environments) and are highly biocompatible due to the sensitive nature of amphibian skin. This work demonstrates for the first time that nests of the túngara frog (Engystomops pustulosus) are stable ex situ with useful physiochemical and biocompatible properties and are capable of encapsulating a range of compounds, including antibiotics. These protein foam mixtures share some properties with pharmaceutical foams and may find utility in a range of pharmaceutical applications such as topical drug delivery systems.

Biological Performance of Electrospun Polymer Fibres.

The evaluation of biological responses to polymeric scaffolds are important, given that the ideal scaffold should be biocompatible, biodegradable, promote cell adhesion and aid cell proliferation. The primary goal of this research was to measure the biological responses of cells against various polymeric and collagen electrospun scaffolds (polycaprolactone (PCL) and polylactic acid (PLA) polymers: PCL⁻drug, PCL⁻collagen⁻drug, PLA⁻drug and PLA⁻collagen⁻drug); cell proliferation was measured with a cell adhesion assay and cell viability using 5-bromo-2'-deoxyuridine (BrdU) and resazurin assays. The results demonstrated that there is a distinct lack of growth of cells against any irgasan (IRG) loaded scaffolds and far greater adhesion of cells against levofloxacin (LEVO) loaded scaffolds. Fourteen-day studies revealed a significant increase in cell growth after a 7-day period. The addition of collagen in the formulations did not promote greater cell adhesion. Cell viability studies revealed the levels of IRG used in scaffolds were toxic to cells, with the concentration used 475 times higher than the EC50 value for IRG. It was concluded that the negatively charged carboxylic acid group found in LEVO is attracting positively charged fibronectin, which in turn is attracting the cell to adhere to the adsorbed proteins on the surface of the scaffold. Overall, the biological studies examined in this paper are valuable as preliminary data for potential further studies into more complex aspects of cell behaviour with polymeric scaffolds.

Electrospun collagen-based nanofibres: A sustainable material for improved antibiotic utilisation in tissue engineering applications.

For the creation of scaffolds in tissue engineering applications, it is essential to control the physical morphology of fibres and to choose compositions which do not disturb normal physiological function. Collagen, the most abundant protein in the human body, is a well-established biopolymer used in electrospinning compositions. It shows high in-vivo stability and is able to maintain a high biomechanical strength over time. In this study, the effects of collagen type I in polylactic acid-drug electrospun scaffolds for tissue engineering applications are examined. The samples produced were subsequently characterised using a range of techniques. Scanning electron microscopy analysis shows that the fibre morphologies varied across PLA-drug and PLA-collagen-drug samples - the addition of collagen caused a decrease in average fibre diameter by nearly half, and produced nanofibres. Atomic force microscopy imaging revealed collagen-banding patterns which show the successful integration of collagen with PLA. Solid-state characterisation suggested a chemical interaction between PLA and drug compounds, irgasan and levofloxacin, and the collagen increased the amorphous regions within the samples. Surface energy analysis of drug powders showed a higher dispersive surface energy of levofloxacin compared with irgasan, and contact angle goniometry showed an increase in hydrophobicity in PLA-collagen-drug samples. The antibacterial studies showed a high efficacy of resistance against the growth of both E. coli and S. Aureus, except with PLA-collagen-LEVO which showed a regrowth of bacteria after 48h. This can be attributed to the low drug release percentage incorporated into the nanofibre during the in vitro release study. However, the studies did show that collagen helped shift both drugs into sustained release behaviour. These ideal modifications to electrospun scaffolds may prove useful in further research regarding the acceptance of human tissue by inhibiting the potential for bacterial infection.

Fabrication and characterisation of drug-loaded electrospun polymeric nanofibers for controlled release in hernia repair.

The chemical distribution and mechanical effects of drug compounds in loaded electrospun scaffolds, a potential material for hernia repair mesh, were characterised and the efficacy of the material was evaluated. Polycaprolactone electrospun fibres were loaded with either the antibacterial agent, irgasan, or the broad-spectrum antibiotic, levofloxacin. The samples were subsequently characterised by rheological studies, scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle goniometry (CAG), in vitro drug release studies, antibacterial studies and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Increased linear viscoelastic regions observed in the rheometry studies suggest that both irgasan and levofloxacin alter the internal structure of the native polymeric matrix. In vitro drug release studies from the loaded polymeric matrix showed significant differences in release rates for the two drug compounds under investigation. Irgasan showed sustained release, most likely driven by molecular diffusion through the scaffold. Conversely, levofloxacin exhibited a burst release profile indicative of phase separation at the edge of the fibres. Two scaffold types successfully inhibited bacterial growth when tested with strains of E. coli and S. aureus. Electrospinning drug-loaded polyester fibres is an alternative, feasible and effective method for fabricating non-woven fibrous meshes for controlled release in hernia repair.