Marine biofouling has serious negative effects on the environment, economy, and the energy sector. The scientific community has acknowledged the anti-adhesive and antimicrobial qualities of carbon nanostructures, such as diamond, fullerenes, graphene, and carbon nanotubes (CNTs).
Carbon Nanotubes (CNTs)
CNTs are promising nanomaterials for various applications, particularly in the medical, environmental, and industrial domains. This is because of their structural stability, high thermal conductivity, and exceptional tensile strength.
CNTs have previously been tested within composite materials that come into contact with saltwater, creating antifouling surfaces to prevent biofouling, primarily to safeguard ship hulls. CNTs have also been shown to affect the structure of marine biofilms and the colonization of macrofouling organisms.
Single-Walled Carbon Nanotubes (SWCNTs) and Multi-Walled Carbon Nanotubes (MWCNTs)
Single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) are two different types of CNTs. These carbon nanomaterials have a concentric cylindrical shape, with a length of several microns that may be increased by up to a few millimeters and a diameter on the order of nanometers that varies depending on the number of walls.
The principal effects of marine biofouling are caused by the attachment of macrofoulers, such as calcareous hard-fouling animals (tubeworms, mussels, and barnacles) and soft-fouling species (hydroids, tunicates, anemones, sponges and non-calcareous algae).
In addition, microfoulers like diatoms, cyanobacteria, and bacteria may inhibit adhesion and biofilm formation, which slows biofouling’s advancement to later stages. A fuller understanding of biofilm behavior and how it interacts with the environment will make it possible to create effective methods for preventing biofouling and reducing its harmful effects.
Optical Coherence Tomography (OCT)
The technical advancement of the field of biofilm research has been facilitated by molecular biology techniques, biochemical processes, and new imaging technologies. In contrast to certain time-consuming and damaging approaches to biofilm research, such as some microscopic techniques, optical coherence tomography (OCT) is an intriguing modality.
In addition to the time-consuming sample preparation, most of the pertinent microscopic methods used to research biofilms call for the costly staining or usage of fluorochromes, which may affect the local features of the biofilm.
Additionally, some only provide low-resolution photographs with a limited field of vision (FOV). Due to its ease of use, cheap cost, lack of sample preparation and/or staining requirements, and capacity for in situ, non-invasive, and real-time imaging without changing the biofilm structure, OCT offers several benefits over conventional microscopic approaches.
Developing Novel Analysis Parameters from 3D OCT Imaging
This study aims to create new analytical criteria based on 3D OCT imaging to assess the biofilm. The study is particularly pertinent since OCT is an in situ, non-destructive method that can be used in various domains. This is the first investigation into how CNT-modified surfaces affect the behavior of cyanobacterial biofilms in an in vitro setting that closely resembles the hydrodynamic conditions seen in actual marine habitats.
Two control surfaces and a CNT composite were utilized to evaluate the surface antifouling efficacy on cyanobacterial biofilm formation. CNT composites, epoxy resin, and glass surfaces were evaluated for their wettability by measuring their contact angles with water.
Contact Bruker Catalyst microscopes were used to conduct AFM experiments. The surface roughness of two samples of each material was evaluated using a random sample area at room temperature. SEM was used to evaluate the surface morphology with nanoscale precision.
Assessing Biofilm Formation
Biofilm formation was assessed on agitated 12-well microtiter plates under optimized settings for cyanobacterial biofilm growth to simulate the hydrodynamic conditions prevalent in marine habitats.
First, clear double-sided sticky tape was applied in the wells to secure the coupons. After sterilizing all coupons and plates using ultraviolet light, the sterile coupons were fastened. Every seven days, two coupons of each surface were tested for the presence of biofilm.
Biofilms of cyanobacteria were photographed and examined. Each coupon underwent two-dimensional (2D) and three-dimensional (3D) imaging with a minimum of two fields of view (FOVs) to ensure the correctness and dependability of the acquired findings.
Significant Findings of the Study
A set of unique structural metrics derived from OCT imaging was constructed to measure the marine biofilm structure over time and on three distinct surface materials, one known to have antifouling activity. The maturity stage of the cyanobacterial biofilm was delayed by surfaces treated with CNTs.
Compared to biofilms that grew on epoxy resin and glass, those that developed on the composite had lower biovolume, thickness, and wet weight and were less porous and smoother.
Improved knowledge of the biofilm growth process in many environments, particularly the marine environment, is made possible by analyzing unique characteristics derived by OCT imaging.
Maria J. Romeu, Marta Lima , Luciana C. Gomes , Ed. D. de Jong, João Morais , Vítor Vasconcelos, Manuel F. R. Pereira , Olívia S. G. P. Soares , Jelmer Sjollema and Filipe J. Mergulhão (2022) The Use of 3D Optical Coherence Tomography to Analyze the Architecture of Cyanobacterial Biofilms Formed on a Carbon Nanotube Composite. Polymers. https://www.mdpi.com/2073-4360/14/20/4410