Chitosan-based matrix as a carrier for bacteriophages

Due to the increasing occurrence of bacterial resistance, alternatives to antibiotics are urgently needed. The study presented here therefore aims to develop an antimicrobial chitosan film loaded with bacteriophages.

Chitosan as a matrix material for antibacterial applications with bacteriophages

Sikora, M., Wąsik, S., Semaniak, J. et al. Chitosan-based matrix as a carrier for bacteriophages. Appl Microbiol Biotechnol 108, 1–16 (2024). https://doi.org/10.1007/s00253-023-12838-0

Due to the growing number of bacterial resistances to antibiotics, research into alternatives such as phages, antimicrobial peptides or nanoparticles is becoming more and more important. Lytic phages can be used as natural agents against specific bacterial strains. In addition to their specificity, they have the advantage of multiplying specifically where bacteria are present, thereby increasing their effect at the site of infection itself. In order to be able to use phages as antibacterial agents, they must be embedded in a suitable matrix. The matrix has to ensure that the phages are sufficiently available, have a certain activity and guarantee stability. Suitable matrix materials are, for example, hydrogels, creams, ointments, films or membranes as carriers of the phages at the target site.

The oral administration of phages is rather difficult because the matrix must ensure stability under extreme conditions such as gastric acid or enzymes in the digestive tract. For this reason, application via the respiratory tract or the skin is of particular interest. But even there, various difficulties have to be overcome, such as matrix stability and the release of phages. A promising matrix for application on the skin, e.g. for infected wounds, is the use of films or membranes. By immobilizing the phages in the film, they can interact directly with the bacteria in the wound. If a hydrophilic matrix is used, the bacteria diffuse from the wound into the polymer film where they can be inactivated by the phages.

Microcrystalline chitosan is a promising matrix material. Chitosan is a natural polymer with versatile properties that can be used in a wide variety of areas. For example, it is non-toxic, easily degradable, easy to modify and has an antibacterial effect. It also has hemostatic and wound-healing properties and, when applied as a thin film, can reduce itching and pain. Due to the positive charge of the polymer, negatively charged micro- and macromolecules can be immobilized well in a chitosan matrix. Thus, chitosan is a good candidate for the design of novel wound dressings and as a carrier for active components with antibacterial properties. In combination with e.g. phages as active components, it is important to match the physiochemical properties of the membrane matrix and the biological properties of the phages in order to achieve a suitable efficiency at the target site.

In the following study, a chitosan-based wound dressing in film form is to be loaded with active, lytic phages in order to improve its antibacterial properties. A chitosan with a molecular weight of 235 kDa and a degree of deacetylation of 86.8 % was used. A comparable product from HMC is Chitosan 85/500. The chitosan matrix was loaded with one of three lytic Pseudomonas aeruginosa phages (KT28, KTN4 and LUZ19), which differ in taxonomic classification, capsid size and morphology, as well as the recognized receptors. The release profiles and possible interactions with the chitosan matrix were investigated. Subsequently, the antibacterial properties against P. aeruginosa were also investigated.

RESULTS

• Synthesis of three different matrix compositions → 1.5 % microcrystalline chitosan with glycerol (ratio 1:0.6) showed the highest flexibility and was selected for further experiments
• Good binding properties of phages to the matrix
• High absorption capacity of water of the matrix before and after addition of the phages, correlated with the type of binding between phages and matrix
• SEM showed an uneven surface of the matrix→ ideal for better adhesion to the wound surface
• Antibacterial activity of the phage-loaded matrix against P. aeruginosa
• Only a small number of virons were released from the matrix, FTIR showed that the positively charged chitosan components and the negatively charged capsids of the phages led to a strong adsorption of the phages to the matrix molecules

Conclusions: In the presented study, an antipseudomonal phage-loaded chitosan film was successfully prepared. Due to the good swelling capacity of the film and the binding between positively-charged chitosan and negatively-charged phages, it was possible to absorb P. aeruginosa and enable the antibacterial effect directly at the matrix.

Link to article: Chitosan-based matrix as a carrier for bacteriophages | Applied Microbiology and Biotechnology (springer.com)