The Use of 3D Optical Coherence Tomography to Analyze the Architecture of Cyanobacterial Biofilms Formed on a Carbon Nanotube Composite

Abstract

The development of environmentally friendly antifouling strategies for marine applications is of paramount importance, and the fabrication of innovative nanocomposite coatings is a promising approach. Moreover, since Optical Coherence Tomography (OCT) is a powerful imaging technique in biofilm science, the improvement of its analytical power is required to better evaluate the biofilm structure under different scenarios. In this study, the effect of carbon nanotube (CNT)-modified surfaces in cyanobacterial biofilm development was assessed over a long-term assay under controlled hydrodynamic conditions. Their impact on the cyanobacterial biofilm architecture was evaluated by novel parameters obtained from three-dimensional (3D) OCT analysis, such as the contour coefficient, total biofilm volume, biovolume, volume of non-connected pores, and the average size of non-connected pores. The results showed that CNTs incorporated into a commercially used epoxy resin (CNT composite) had a higher antifouling effect at the biofilm maturation stage compared to pristine epoxy resin. Along with a delay in biofilm development, a decrease in biofilm wet weight, thickness, and biovolume was also achieved with the CNT composite compared to epoxy resin and glass (control surfaces). Additionally, biofilms developed on the CNT composite were smoother and presented a lower porosity and a strictly packed structure when compared with those formed on the control surfaces. The novel biofilm parameters obtained from 3D OCT imaging are extremely important when evaluating the biofilm architecture and behavior under different scenarios beyond marine applications.

3D Optical Coherence Tomography image processing in BISCAP: characterization of biofilm structure and properties

“…Significantly lower biofilm porosity values (∼0.1 in shallow mode) were obtained from the 3D OCT images using BISCAP. Those values, although very low, are closer to the porosities reported in Romeu et al (2022) (also from 3D OCT image processing), ranging between 0.2 and 0.4. Those differences might be due to the biofilm structure or the conceptual interpretation of porosity calculations.…”

“…Using these arrays, it is possible to calculate several biofilm structural parameters. Consistently with Narciso et al (2022) and Romeu et al (2022) , biofilm thickness ( L F ) is calculated as follows: …”

Graphene-Based Coating to Mitigate Biofilm Development in Marine Environments

“…Moreover, the biovolume of biofilms formed on both surfaces was calculated for incubation day 42 ( Figure 6 a). This parameter provides an estimate of the biomass in the biofilm (µm 3 ) per area of the region of interest (mm 2 ) [ 31 ]. Results showed that the biofilms formed on G5/PDMS had significantly lower biovolume than those developed on the control surface (on average, 1.80 × 10 8 µm 3 ·mm −2 for PDMS versus 8.89 × 10 7 µm 3 ·mm −2 for G5/PDMS; p ≤ 0.01).…”

“…In order to further assess biofilm architecture, for the last sampling day, biofilm porosity and biofilm biovolume were determined as described by Romeu et al [ 31 ]. The percentage of biofilm porosity corresponds to the ratio between the volume of non-connected pores and the total biofilm volume, whereas biovolume pertains to the total biofilm volume per area of the region of interest.…”

“…In fact, the incorporation of nanomaterials into marine antifouling paints has been reported to greatly impact a surface’s charge potential, hydrophobicity, and topography, as well as its antibacterial and anticorrosion properties [ 28 , 29 ]. Among these emerging nanoengineered antifouling paints, those containing carbon nanomaterials, such as carbon nanotubes and graphene, have shown promising results [ 30 , 31 , 32 ].…”