Abstract
The development of photoacoustic systems is important for the real-time detection of cysteine (Cys), a biothiol in biological systems that serves as a significant biomarker for human health. Advanced photoacoustic (PA) signals with colloidal plasmonic Au nanomaterials rely on the efficient conversion of light to energy waves under moderately pulsed laser irradiation. In this study, we synthesized Cys-capped Au nanorods (Au@Cys NRs) and Cys-capped Au nanoparticles (Au@Cys NPs) through a conjugate of three Cys concentrations (10, 100, and 1000 μM). These plasmonic Au nanomaterials can be used as a PA resonance reagent due to their maximum localized surface plasmon resonance (LSPR) absorption bands at 650 nm and 520 nm in Au NRs and Au NPs, respectively. Subsequently, the PA signals were noticeably increased proportionally to the concentrations in the Au@Cys NRs and Au@Cys NPs under 658 nm and 520 nm laser irradiation, respectively, according to our portable photoacoustic system. Furthermore, PA signal amplitudes in Cys detection are boosted by ~233.01% with Au@Cys NRs and ~102.84% with Au@Cys NPs enhancement, compared to free Cys, according to ultrasound transducers at frequencies of 3 MHz.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
The results show that the changes of the PA amplitudes and histogram widths of Cys and the Au@Cys NPs were subtle for the three different concentrations
Cys-capped Au nanorods (Au NRs) and Au NP colloids in water can act as a PA wave resonant enhancer under suitable localized surface plasmon resonance (LSPR) wavelengths, with regard to Au NRs and Au NPs at 658 nm and 520 nm laser treatment
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Cysteine (Cys) is a crucial thiol-containing amino acid which plays a critical role in human pathologies [1,2], and is found in huge quantities in protein-rich foods [3]. Cys participates in many important and essential biological functions, including protein synthesis, detoxification, and metabolism [4]. The concentrations of Cys are maintained at around 30–200 μM for the synthesis of various proteins, serving as the source of sulfide in human metabolism [5]. A lack of Cys in the human body often leads to liver damage and edema, among other effects, while the presence of excessive Cys is associated with neurotoxicity, including Parkinson’s disease and Alzheimer’s disease [6]
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