# PSA-Responsive Aptamer-Based Switchable Aggregates of Ultrasmall Gold Nanoparticles

## TL;DR

This paper introduces a new method using gold nanoparticles and aptamers to detect prostate-specific antigen, which could lead to better diagnostic tools for prostate cancer.

## Contribution

The study presents a novel PSA-responsive aptamer-based system using ultrasmall gold nanoparticles for sensitive and selective detection.

## Key findings

- The system detects PSA at concentrations as low as 10 fM in buffers and 1 pM in blood-mimicking conditions.
- The aggregates disassemble selectively in the presence of PSA, demonstrating high specificity.
- Optimization strategies are proposed to improve in vivo applicability of the system.

## Abstract

Prostate-specific antigen (PSA) is a key biomarker for the early detection of prostate cancer recurrence following surgical treatment. In this study, we present a PSA-responsive, aptamer-based switchable aggregate system, named AS2-US-AuNP-Aggregate, composed of ultrasmall gold nanoparticles (US-AuNPs) linked by (partially) pairing oligomers that selectively disassemble in the presence of PSA. The system was optimised also using a previously developed in silico routine and is designed for enhanced detection capabilities and for supporting in vivo applicability. We measured the sizes of the nanosystems by dynamic light scattering (DLS) and their extinction spectra, also in the presence of PSA in simple buffers, in the presence of DNaseI, and under blood-mimicking conditions (filtered plasma), obtaining a response down to 10 fM PSA in buffers and to 1 pM in filtered plasma. Our findings highlight the potential of aptamer-based nanoparticle aggregates as a basis for user-friendly diagnostic tools. Additionally, we discuss key optimisation strategies to further advance their development for in vivo diagnostic applications.