Applications of Surface Second Harmonic Generation in Biological Sensing

Abstract

Surface second harmonic generation (SHG) is a coherent, nonlinear optical technique that is well suited for investigations of biomolecular interactions at interfaces. SHG is surface specific due to the intrinsic symmetry constraints on the nonlinear process, providing a distinct analytical advantage over linear spectroscopic methods, such as fluorescence and UV-Visible absorbance spectroscopies. SHG has the ability to detect low concentrations of analytes, such as proteins, peptides, and small molecules, due to its high sensitivity, and the second harmonic response can be enhanced through the use of target molecules that are resonant with the incident (ω) and/or second harmonic (2ω) frequencies. This review describes the theoretical background of SHG, and then it discusses its sensitivity, limit of detection, and the implementation of the method. It also encompasses the applications of surface SHG directed at the study of protein-surface, small-molecule-surface, and nanoparticle-membrane interactions, as well as molecular chirality, imaging, and immunoassays. The versatility, high sensitivity, and surface specificity of SHG show great potential for developments in biosensors and bioassays.

Resource‐Efficient Low‐Temperature Synthesis of Microcrystalline Pb2B5O9X (X = Cl, Br) for Surfaces Studies by Optical Second Harmonic Generation

“…Optical second harmonic generation (SHG) is an advancing technique for studying surfaces and interfaces such as monitoring chemical reactions with picosecond time resolution, in situ (photo‐) catalysis investigations and biological sensing. [ 1–7 ] Surface science figured significantly in disciplines ranging from chemistry and physics to biology and electronics, where reliable characterization of surfaces and interfaces is of great importance. Among all the tools developed for surfaces analysis over the years (e.g., electron scattering and diffraction, photoemission, and mass spectroscopy), SHG receives much attention due to its nondestructive measurement principle and wide applicability.…”

Optimization of interstrand interactions enables burn detection with a collagen-mimetic peptide

“…Second harmonic generation (SHG) microscopy is a nonlinear optical method that is used extensively to identify and visualize fibrillar collagens in tissues. [45][46][47] Using a multiphoton laser-scanning microscope, data can be acquired from both SHG and Cy5 channels, revealing the distinction between damaged and healthy collagen (SHG) and its detection with our probe (Cy5). The fibrils exposed to 350°C show little or no signal through the SHG channel, confirming the absence of intact collagen structure in the burn area (Fig.…”

Second harmonic generation detection of Ras conformational changes and discovery of a small molecule binder

“…Second harmonic generation (SHG) is a sensitive biophysical technique that detects real-time changes in protein conformation under dynamic conditions (13,14). In SHG, 2 photons of equal energy are combined by a nonlinear material to emit a single photon with twice the energy.…”