| Summary: | Extracted from green plants, Photosystem I (PSI) is a nanoscale protein complex that can be incorporated into biohybrid devices to convert solar irradiation into usable power. In previous research, our group has shown that multilayer films of PSI that range in thickness from 1-3 μm generate photocurrent that increases with film thickness when deposited onto an electrode and exposed to an aqueous solution of redox species (i.e. a wet cell). However, long-term experiments have shown that the photocurrents of wet cells decrease over the first few days, which has been attributed to the desorption of some PSI proteins exposed to the mediator solution. This decrease of the film thickness reduces the photocurrent generation. Particular molecules can cross-link protein molecules via covalent bonds, as a promising strategy to stabilize PSI in these multilayer films. Three different cross-linkers, glutaraldehyde (GA), terephthalaldehyde (TPDA) and 2-iminothiolane (2IT, trauts reagent), were investigated here to stabilize multilayer PSI films that were deposited onto gold substrates. The thickness, uniformity, and photocurrent of PSI films were analyzed at various conditions. Results showed that the thickness remaining of all cross-linked PSI films was superior to that of non cross-linked films. PSI films modified by 1 mM 2IT exhibited the best performance in terms of both the stability of thickness and photocurrent. This study provides guidance toward selection of an appropriate cross-linker to strengthen PSI films and maintain their electrochemical performance.
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