Antimicrobial photodynamic inactivation represents a promising and potentially greener alternative to conventional antimicrobials, and a solution for multidrug-resistant strains. The current study reports the development and characterization of tetra-substituted diazirine porphyrin covalently bonded to polyethylene terephthalate (PET) and its use as an antimicrobial surface. The diazirine moiety on the porphyrin was activated using a temperature of 120 °C, which initiated a C–H insertion mechanism that irreversibly functionalized the PET surface. Activation of the surface with white LED light in phosphate-buffered saline (PBS) led to singlet oxygen generation, which was detected via the degradation of 9,10-anthracenediylbis(methylene)dimalonic acid (ADMA) over time. The bactericidal effect of the 1 O 2 -producing surface against Staphylococcus aureus was determined qualitatively and quantitatively. The growth of the pathogen beneath porphyrin-functionalized PET coupons was reduced; moreover, the PET coupons resulted in a 1.76-log reduction in cell counts after exposure to white LED light for 6 h. This is a promising material and platform for the development of safer antimicrobial surfaces, with applications in healthcare, food packaging, marine surfaces, and other surfaces in the environment.

Remell™ Mueller Hinton broth with cations (CAMHB) powder (Thermo Fisher Scientific, MA, USA) was dissolved in DI water according the manufacturer's directions and autoclaved before use. Overnight cultures were made by inoculating 5 mL of CAMHB solution with an isolated colony of Pseudomonas aeruginosa (Schroeter) Migula (ATCC® 10145™) (University of Victoria, BC, CA) (from an existing streak plate) via a disposable inoculating loop. The inoculated culture was vortexed (VWR, Fixed Speed Vortex Mixer) then incubated for 18 hours in a 37°C shaker incubator set at 200 rpm (VWR, 1575 Incubator Shaker).Overnight cultures were used for both the biofilm prevention protocol and the biofilm removal protocol. The overnight cultures were processed for use in each protocol by centrifuging (Beckman Coulter, Allegra X-12R) the overnight culture at 2095 ×g (Relative Centrifugal Force) for 8 minutes at approximately 21°C, to pellet P. aeruginosa. Longer centrifugation times tended to cause the pellets to be too difficult to break up in a later step. The supernatant was then decanted and the pellet was resuspended in 5 mL of CAMHB via vortexing.

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Biofouling of polyamide membranes is one of the main barriers faced by reverse osmosis (RO) technologies to supply fresh water. Currently, biofouling is addressed by feed water pretreatment using chlorine, followed by membrane cleaning. Chlorine damages polyamide membranes and also generates harmful disinfection byproducts. Thus, safer strategies are needed to prevent biofouling in polyamide membrane systems. This review investigates the applicability of the following non-oxidizing biocides in preventing and controlling biofouling in RO systems, including their antimicrobial efficiency, hazard levels, membrane compatibility, and applicability to drinking water treatment: (1) 2,2-dibromo-3-nitropropionamide (DBNPA); (2) 2-methyl-4-isothiazolin-3-one (MIT); (3) sodium bisulfite (SBS), (4) phenoxyethanol (PE), (5) sodium benzoate (SB). According to this review, MIT and DBNPA present most of the features attributed to an ideal anti-biofouling chemical but also are the most hazardous biocides. Due to safety and efficacy, none of the five chemicals were determined to be the final solution to address membrane biofouling. However, alternative RO biocide research is in early development and requires further investigation via biofouling prevention studies. Therefore, future research efforts on the investigation of economic, eco-friendly, and safe antifouling agents to prevent and treat biofouling in RO systems are paramount to promote sustainable water supply in water-stressed countries.

As potable water scarcity increases across the globe; it is imperative to identify energy and cost-effective processes for producing drinking-water from non-traditional sources. One established method is desalination of brackish and seawater via reverse osmosis (RO). However, the buildup of microorganisms at the water-membrane interface, known as biofouling, clogs RO membranes over time, increasing energy requirements and cost. To investigate biofouling mitigation methods, studies tend to focus on single-species biofilms; choice of organism is crucial to producing useful results. To determine a best-practice organism for studying antimicrobial treatment of biofilms, with specific interest in biofouling of RO membranes, we answered the following two questions, each via its own semi-systematic review: 1. Which organisms are commonly used to test antimicrobial efficacy against biofilms on RO membranes? 2. Which organisms are commonly identified via genetic analysis in biofilms on RO membranes? We then critically review the results of two semi-systematic reviews to identify pioneer organisms from the listed species. We focus on pioneer organisms because they initiate biofilm formation, therefore, inhibiting these organisms specifically may limit biofilm formation in the first place. Based on the analysis of the results, we recommend utilizing Pseudomonas aeruginosa for future single-species studies focused on biofilm treatment including, but not limited to, biofouling of RO membranes.