Visible light mediated killing of multidrug-resistant bacteria using photoacids

Abstract

Increasing acidity is a promising method for bacterial inactivation by inhibiting the synthesis of intracellular proteins at low pH. However, conventional ways of pH control are not reversible, which can cause continuous changes in cellular and biological behaviours and are harmful to the host. Utilizing a photoacid that can reversibly alter pH over two units, we demonstrated a strong bacterial inhibition assisted by visible light.The pH value of the solution reverts back to the original level immediately after the irradiation is stopped.If a photoacid is combined with colistin, the minimum inhibitory concentration (MIC) of colistin on multidrug-resistant (MDR) Pseudomonas aeruginosa can be improved $32 times (from 8 to 0.25 mg mL À1 ), which significantly decreases the toxicity of colistin in clinics. Evidenced by the extremely low toxicity of the photoacid, this strategy is promising in MDR bacteria killing.

Stability of merocyanine-type photoacids in aqueous solutions

“…PAH1 in Figure is the most studied metastable‐state photoacid and has been used in many applications . Therefore, its decomposition in aqueous solutions was studied in this work.…”

“…Over the past few years, protonated merocyanines (MEHs) have been used as photoacids for reversible control of proton concentration using light. Because of their ability of creating a large pH change, visible‐light sensitivity, and good reversibility, this type of photoacid has been used to control acid‐catalyzed reactions, volume‐change of hydrogels, polymer conductivity, bacteria killing, odorant release, and color change of materials . Other applications including control of supramolecular assemblies, molecular switches, microbial fuel cells cationic sensors, and nanoparticle assemblies have also been demonstrated recently.…”

Effects of Substituents on Metastable‐State Photoacids: Design, Synthesis, and Evaluation of their Photochemical Properties

“…Last, but not least, Liao and co‐workers reported a metastable‐state photoacid that could reversibly undergo proton photodissociation accompanied with a nucleophilic reaction to form a cyclic spiropyran upon irradiation with a moderate intensity of visible light and thermal recovery in the dark. Given its high efficiency (a pH change of 2.2 units), long lifetime ( t 1/2 =76 s), and good reversibility, this metastable‐state photoacid has attracted considerable attention and has been utilized in various fields, such as the control of acid‐catalyzed reactions, supramolecular assemblies, microbial fuel cells, bacteria killing, waste management of reactions, cationic sensors, odorant release, and biological function . Recently, our group successfully extended the application of this photoacid to visible‐light‐responsive rewritable paper .…”

Controlled Release of Fragrant Molecules with Visible Light

“…Our approach is based on photocontrolled hydrolysis catalyzed by a metastable-state photoacid. [5][6][7][8][9] Metastable-state photoacids can reversibly change the pH of an aqueous solution by more than two units under visible light with moderate intensity. We hypothesize that the photo-acidity should be enough to induce hydrolysis of some acid-sensitive groups.…”