Optical Aggregation of Gold Nanoparticles for SERS Detection of Proteins and Toxins in Liquid Environment: Towards Ultrasensitive and Selective Detection

Optical tweezers and their applications

“…A N U S C R I P T In this context, it has been shown that surface-enhanced Raman scattering [79] (SERS)-active aggregates can be created on glass substrates by optical manipulation of gold nanorods (AuNRs) in a liquid environment [232,233] containing biomolecules. In fact, due to their very large extinction cross-sections, these…”

“…AuNRs cannot be optically trapped with visible wavelengths [232]. However, they can be pushed towards the sample chamber glass walls where they aggre- on amino-acids such as phenylalanine [232] and enzymes such as lysozime [232] and catalase [233] have been also reported [232]. This molecular detection tech-…”

“…nique can be also made protein-selective by functionalizing the AuNRs with aptamers, which capture a target biomolecule. Proof-of-concept results have 850 been obtained with ochratoxin A[233], a nephrotic mycotoxin which may contaminate food commodities and wine representing potential public health risk.With this methodology, the toxin has been detected in liquid environment at concentrations as low as 1 µM[233].Optical positioning of AuNRs is particularly interesting because it is a low 855 cost alternative to much more complex litographic techniques. As a further advantage, it allows an easy and fast way to decorate with metallic particles also not flat substrates, such as three dimensional micro-and nanostructures obtained with direct laser writing by two-photon photopolymerization (TPP)[234,235,236, 237,238,239, 240,241,242], opening the way to the re-860 alization of hybrid metal-polymer devices such as, for example, spectroscopic probes and sensors.…”

Optical tweezers-controlled hotspot for sensitive and reproducible surface-enhanced Raman spectroscopy characterization of native protein structures

“…To address this dilemma, mechanical manipulations are desirable alternatives to create hotspots dynamically at the designated location 7 , 30 , 31 . Recently, optical tweezers-assisted SERS has been developed to increase the efficiency for the SERS analysis in aqueous conditions 32 – 41 , by introducing the additional trapping laser beams to manipulate SERS substrates 42 , 43 . Kall and co-workers utilized optical tweezers to bring two AgNPs together to form a SERS active dimer 44 , but the hotspot size and the precise location was uncertain due to the diffraction limit of optical microscope 44 .…”

Plasmonic microbubbles: nucleation, growth and collapse

“…The unique characteristics of plasmonics lead to a broad range of applications across many different fields, such as biomedicine and biotechnology [35,[40][41][42][43], sensing and imaging [43][44][45][46], enhanced chemical reactions [47][48][49][50][51][52] and surface-enhanced Raman scattering [45,53,54], solar energy conversion [55][56][57], among others [34,43,45,58,59].…”