UIUC nanoassemblies point to novel, sensitive biosensors

03 Jul 2025

Better control over light-matter interactions could assist early detection of disease.

A project at the University of Illinois Urbana-Champaign (UIUC) has developed a way to enhance fluorescence from the tags used to detect biomarkers for disease.

Discussed in APL Materials, the findings build on earlier UIUC work on photonic-crystal-enhanced fluorescence (PCEF).

The PCEF effect occurs when the fluorescence from a particular marker is amplified by surface plasmon-coupled effects, created on the material's metal thin-film substrate.

In principle this can augment the intrinsic fluorescence considerably, although challenges of low sensitivity, experimental artefacts and quenching from the plasmonic gold nanoparticles used in the material have remained.

UIUC previously showed that creating cryosets, particular nanoassemblies of gold nanoparticles created through rapid cryogenic freezing, could help tackle these issues, by creating gaps in the structure that reduced the quenching and enhanced light-matter interactions.

Now UIUC has gone further, by introducing a new class of cryosoret nanoassemblies based on Fe₃O₄-Au, that not only dequench the fluorescence signal but also allow the emission output to be directionally steered.

"It's about engineering optical behavior, both structurally and functionally, through deliberate design," commented Seemesh Bhaskar from UIUC. "Self-assembly is a fundamental principle of nature. What individual nanoparticles cannot accomplish alone becomes possible through their collective organization."

Point-of-care medical diagnostics

In trials, integrating these nanoassemblies onto a photonic crystal interface proved to be a route to harnessing both the electric and magnetic components of light. When tested using a common fluorophore, the fluorescence was enhanced by a factor of 200 compared to the photonic crystal alone.

This showed that fluorescence quenching was effectively minimized, according to UIUC, making this technology a promising avenue for detecting low concentrations of biomarkers, potentially in the attomolar range.

UIUC's next steps will include introducing magnetic tunability into the nanoassemblies, and optimizing the cryosoret nanoassemblies to target specific biomarkers, like microRNAs, circulating tumor DNA, and viral particles, for early detection of cancer and infectious disease.

The long-term goal is development of intellignet, responsive biosensors suitable for use as point-of-care technologies, meeting the pressing need for sensitive, accessible, and deployable biosensing systems.

“"This work represents a hybrid optical platform where photons are not merely emitted, they are orchestrated," said Brian Cunningham, head of UIUC's Nanosensors Group.

"This convergence of photonic-plasmonic simulations, advanced nanofabrication, and chemical engineering principles has far-reaching implications, particularly in the realm of medical diagnostics."