Introduction: Polymer microarrays are a key enabling technology for the discovery of new biomaterials and have been utilised to identify novel polymers that resist bacterial attachment[1],[2]. The hundreds of polymer-bacteria interactions observed on a microarray can be used to elucidate underlying structure-function relationships[3]. A number of different modelling strategies have been employed to predict bacterial attachment using either surface chemistry or bulk composition. New insight into the attachment process can be obtained by analysing the models produced. In this presentation the roadmap for developing novel biomaterials will be outlined, as depicted in Fig. 1.
Figure 1 – Schematic outline of the roadmap used for the discovery of novel biomaterials.
Methods: Polymer microarrays were formed using a XYZ3200 workstation (Biodot) using slotted metal pins with UV curing. Polymerisation solution was composed of 75% (v/v) monomer, 25% (v/v) DMF and 1% (w/v) photoinitiator. A bacterial attachment assay was developed using green fluorescing protein tagged bacterial strains (Pseudomonas aeruginosa PAO1, Staphylococcus aureus 8325-4, Uropathogenic Escherichia coli). Time-of-Flight Secondary Ion Mass Spectrometry was conducted using an IONTOF IV instrument. For modelling, molecular descriptors were generated using Dragon v. 5.516 and Adriana v. 2.217. Partial least square models were generated using the Eigenvector PLS_Toolbox 3.5.
Results: Polymer microarrays were used for the discovery of novel materials that resist bacterial attachment. Using this approach over 1200 unique materials were screened to identify a hit polymer that was able to reduce bacterial attachment by up to 99% compared with silicone. The ‘hit’ material was able to reduce infection in vivo on subcutaneous implants within a mouse model (Fig. 2)[2].
Figure 2 – Summary of high throughput method to discover a material resistant to bacterial attachment, from the polymer microarray to in vivo application.
The biological response to the array of materials was successfully modelled to both surface chemistry as measured by ToF-SIMS[2] and bulk composition as represented by molecular descriptors[4],[5]. The models were used to screen virtual libraries of materials to identify novel materials predicted to have optimised resistance to bacterial attachment. Further, the chemical fragments and molecular descriptors associated with low bacterial attachment within the models provided insight into the physio-chemical mechanism by which the polymers resisted bacteria. Specifically, the association of both the hydrophilic ester groups and hydrophobic cyclic hydrocarbon groups with low bacterial attachment suggested that the weakly amphiphilic nature of the polymers was key to their function[2]. Similarly, molecular descriptors associated with hydrophobicity and the number of ester alpha hydrogen atoms were linked with bacterial attachment[4].
Conclusion: Polymer microarrays were successfully applied to discover new materials resistant to bacterial attachment. This was achieved without the requirement for a comprehensive understanding of the underlying material-biological interactions, however, the physio-chemical mechanism was developed subsequently using various modelling procedures. The models produced can be used to predict the next generation of materials resistant to bacterial attachment.
Wellcome Trust (Senior Investigator Award ref: 103882)
References:
[1] Hook, A.L., Cell-Based microarrays - Review of applications, developments and technological advances, E. Palmer, Editor. 2014, Springer p. 53-74.
[2] Hook, A.L., et al., Nature Biotechnology, 2012. 30(9): p. 868-875.
[3] Hook, A.L., D.A. Winkler, and M.R. Alexander, Tissue Engineering, J. De Boer, Editor. 2014, Springer. p. 253-281.
[4] Epa, V.C., et al., Advanced Functional Materials, 2014. 24(14): p. 2085-2093.
[5] Sanni, O., et al., Advanced Healthcare Materials, 2015. 4(5): p. 695-701.