bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/292334

Holographic optical trapping Raman micro-spectroscopy for interacting live cells

Sinjab, F.·Notingher, I.·Elsheikha, H. M.·Awuah, D.·Gibson, G.·Padgett, M.·Ghaemmaghami, A. M.
View original source ↗Export metadata ↓

Abstract

We present a combined holographic optical tweezers and confocal Raman spectroscopy instrument which allows fast, flexible, and interactive manipulation with molecular measurement of interacting live cell systems. Multiple laser foci created using a spatial light modulator are simultaneously used for optical trapping and spontaneous Raman spectroscopy. To enable confocal Raman measurements with high spectral resolution, a digital micro-mirror device was used to generate reflective pinholes which are matched to each laser trap. We demonstrate this unique capability by initiating complex interactions between multiple live cells whilst non-invasively acquiring Raman spectra of the processes with high spatial, spectral, and temporal resolution.

Explore related subjects

biophysicsPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Sinjab, F., Notingher, I., Elsheikha, H. M., Awuah, D., Gibson, G., Padgett, M., Ghaemmaghami, A. M.. 2018-03-30. Holographic optical trapping Raman micro-spectroscopy for interacting live cells. https://doi.org/10.1101/292334

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Kinetic gating by an iron sulfur chain modulates flavin radical-pair spin chemistry in mitochondrial Complex I

Mitochondrial Complex I generates reactive oxygen species at its flavin cofactor, where spin dependent reaction pathways have been proposed. Models of this chemistry treat the flavin oxygen radical pair in isolation, although the flavin is wired to a chain of eight iron sulfur clusters. Here we model the pair with this chain using the human Complex I structure and open quantum system models of spin coupling and electron transfer. In the simulated network, spin coherence decays rapidly along the chain, whereas proximal clusters alter the calculated radical-pair singlet yield. Their influence is kinetically gated: a downstream cluster affects the modelled yield when its electron-transfer rate competes with radical pair recombination, a threshold robust to driving force and to the transfer model. Modelling does set the sign: one directional spin hops predict suppression and inflate coherence transport, whereas charge resolved transfer drives the singlet yield towards its spin-randomized limit unless triplet recombination dominates. Detectable spin dependent effects in this framework require superoxide spin relaxation to be substantially slower than in free solution, a condition not yet established for Complex I.

biophysics↗
bioRxiv2026

Semidilute Polymer Scaling Controls PEG-induced Protein Phase Separation

When does polyethylene glycol (PEG) mass concentration provide a common measure of crowding strength across polymer chain lengths? Here we use bovine serum albumin (BSA) and PEG as a controlled depletion system and measure both coexisting phases to determine binodals, tie lines, and critical points across PEG molecular weights of 4--100 kDa. Phase diagrams for PEG 20, 35, and 100 kDa approximately collapse in mass-concentration coordinates, consistent with semidilute polymer scaling. Generalized free volume theory (GFVT) describes the BSA binodals and tie lines. It also approximately describes binodals for three additional globular proteins in PEG 35K, extending the comparison across proteins spanning 7.2--66.4 kDa. For the binary PEG mixtures tested, GFVT approximates the binodals using an effective polymer size corresponding to the weight-average molecular weight. These results identify a regime in which PEG mass concentration (g/L) provides a transferable measure of depletion-induced crowding.

biophysics↗
bioRxiv2026

Correlation-resolved sum-frequency generation microscopy of biological tissue with bright twin beams

Sum-frequency generation (SFG) driven by bright twin beams generated through high-gain parametric down-conversion comprises a coherent component arising from correlated mode pairs and an incoherent component arising from interactions between uncorrelated modes. Modal correlations can enhance coherent SFG in anisotropic nonlinear media, for example by extending the effective interaction length. Whether such correlations can likewise benefit image formation in heterogeneous biological tissue remains unknown. Here we address this question by performing SFG imaging of biological tissue using bright twin beams as the excitation source. Spectral decomposition of the SFG signal separates its coherent and incoherent components, allowing us to reconstruct co-registered images and examine how twin-beam correlations influence image formation. In mouse skeletal muscle, the coherent-component image revealed sarcomere periodicity with a Bragg-spot-to-background ratio of approximately 310, compared with 7.5 in the incoherent-component image. In fresh human dermis, the coherent-component image showed greater Fourier power than the incoherent-component image in the 0.30-0.50 \mu m^{-1} band and a greater fractional autocovariance decay at short spatial lags. These results demonstrate that twin-beam correlations can enhance contrast and detectability at selected spatial frequencies in heterogeneous tissue. Correlation-resolved SFG microscopy thus offers a route for exploiting bright quantum-light sources in nonlinear optical bioimaging.

biophysics↗