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The polymeric glyco-linker controls the signal outputs for plasmonic gold nanorod biosensors due to biocorona formation.

ABSTRACT: Gold nanorods (GNRs) are a promising platform for nanoplasmonic biosensing. The localised surface plasmon resonance (LSPR) peak of GNRs is located in the near-infrared optical window and is sensitive to local binding events, enabling label-free detection of biomarkers in complex biological fluids. A key challenge in the development of such sensors is achieving target affinity and selectivity, while both minimizing non-specific binding and maintaining colloidal stability. Herein, we reveal how GNRs decorated with galactosamine-terminated polymer ligands display significantly different binding responses in buffer compared to serum, due to biocorona formation, and how biocorona displacement due to lectin binding plays a key role in their optical responses. GNRs were coated with either poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) or poly(N-hydroxyethyl acrylamide) (PHEA) prepared via reversible addition-fragmentation chain-transfer (RAFT) polymerisation and end-functionalised with galactosamine (Gal) as the lectin-targeting unit. In buffer Gal-PHEA-coated GNRs aggregated upon soybean agglutinin (SBA) addition, whereas Gal-PHPMA-coated GNRs exhibited a red-shift of the LSPR spectrum without aggregation. In contrast, when incubated in serum Gal-PHPMA-coated nanorods showed no binding response, while Gal-PHEA GNRs exhibited a dose-dependent blue-shift of the LSPR peak, which is the opposite direction (red-shift) to what was observed in buffer. This differential behaviour was attributed to biocorona formation onto both polymer-coated GNRs, shown by differential centrifugal sedimentation and nanoparticle tracking analysis. Upon addition of SBA to the Gal-PHEA coated nanorods, signal was generated due to displacement of weakly-bound biocorona components by lectin binding. However, in the case of Gal-PHPMA which had a thicker corona, attributed to lower polymer grafting densities, addition of SBA did not lead to biocorona displacement and there was no signal output. These results show that plasmonic optical responses in complex biological media can be significantly affected by biocorona formation, and that biocorona formation itself does not prevent sensing so long as its exact nature (e.g. 'hard versus soft') is tuned.

SUBMITTER: Pancaro A

PROVIDER: S-EPMC8223873 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The assembly of nanostructures with plausible statistical orientations has provided the opportunity to correlate physical observables to develop a diverse range of niche applications. The dimeric configurations of gold nanorods have been chosen as atypical model systems to correlate optoelectronic with mechanical properties at a number of combinations of angular orientations. Metals are considered as conductors in electronics and reflectors in optics - therefore, metallic particles at the nanoscale exhibit unique optoelectronic characteristics that enable the design of materials to meet the demand of the modern world. Gold nanorods have often been adopted as prototypical anisotropic nanostructures owing to their excellent shape-selective plasmonic tunability in the vis-NIR region. When a pair of metallic nanostructures is sufficiently close to exhibit electromagnetic interaction, the evolution of collective plasmon modes, substantial enhancement of the near-field and strong squeezing of the electromagnetic energy at the interparticle spatial region of the dimeric nanostructures occur. The localised surface plasmon resonance energies of the nanostructured dimers strongly depend on the geometry as well as the relative configurations of the neighbouring particle pairs. Recent advances in the 'tips and tricks' guide have even made it possible to assemble anisotropic nanostructures in a colloidal dispersion. The optoelectronic characteristics of gold nanorod homodimers at different mutual orientations with statistical variation of the angle between 0 and 90° at particular interparticle distances have been elucidated from both theoretical and experimental perspectives. It has been observed that the optoelectronic properties are governed by mechanical aspects of the nanorods at different angular orientations of the dimers. Therefore, we have approached the design of an optoelectronic landscape through the correlation of the plasmonics and photocapacitance through the optical torque of gold nanorod dimers.

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The polymeric glyco-linker controls the signal outputs for plasmonic gold nanorod biosensors due to biocorona formation.

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