Abstract
Biofilms are dense bacterial colonies that may adhere to the surfaces of medical devices and are major contributors to infections. These colonies are characterized by a self-produced matrix of extracellular polymeric substances (EPS). Bacterial biofilms are difficult to treat with the commonly used antibiotics partially because of their poor diffusion through the EPS and therefore require new targeted strategies to effectively fight them. Biofilms may produce an acidic microenvironment which can be exploited to design such targeted treatment strategies. However, there is currently a lack of high-throughput ways to determine the acidity of biofilms at their interface with the medical device. Here, a novel all-inorganic pH responsive system is developed from luminescent carbonated hydroxyapatite nanoparticles doped with Eu3+ ions which can determine the biofilm acidity fluorometrically due to carbonate removal in acidic environments that directly affects the nanoparticle luminescence. The pH responsive nanoparticles are in-situ deposited during their production onto substrates on which a variety of clinically-relevant biofilms are grown. The acidity of their interfacial (micro)environment depends on the bacterial species and strain even when differences in biofilm biomass are considered.
Highlights
Bacterial biofilms can form on both patient tissue and medical de vices and are the leading cause of persistent infections in patients (Romling et al, 2014; Romling and Balsalobre, 2012)
The morphology of the calcium phosphate (CaP):Eu3+ nanoparticles (Ca/P 2.19) collected further downstream during their in-situ flame deposition on substrates is evaluated by transmission electron microscopy (TEM) and shown in Fig. 1a, in which an aggregate structure is observed
The crystallinity of the deposited nanoparticle films on the substrates is evaluated by powder X-ray diffraction (XRD)
Summary
Bacterial biofilms can form on both patient tissue and medical de vices (such as titanium implants) and are the leading cause of persistent infections in patients (Romling et al, 2014; Romling and Balsalobre, 2012). These colonies of bacteria adherent to a surface are characterized by a dense self-produced matrix composed of extracellular polymeric substances (EPS). There is a need to identify novel treatment strategies capable of killing established biofilms and/or prevent their formation on abiotic surfaces Several such strategies, as recently reviewed by Koo et al (2017) utilize stimulus-responsive materials that capitalize on pH changes inside the biofilm. The origin of biofilm acidification is attributed mainly to by-products of bacterial carbohydrate metabolism such as acetic and lactic acid, an additional contributing factor may be extra cellular DNA found in the EPS (Schlafer et al, 2018; Wilton et al, 2016)
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