Air-liquid microfluidics-integrated surface-enhanced Raman spectroscopy for selective molecular adsorption and...

Area of Science:

• Microbiology
• Analytical Chemistry
• Biotechnology

Background:

• Accurate bacterial discrimination is vital for diagnosing infections and guiding antibiotic therapy.
• Surface-enhanced Raman spectroscopy (SERS) offers label-free molecular sensing but struggles with complex mixtures and subtle spectral differences, particularly for antibiotic-resistant strains.
• Distinguishing bacterial species with similar purine derivative profiles or varying molecular affinities to SERS substrates remains a challenge.

Purpose of the Study:

• To develop an advanced SERS system for enhanced bacterial discrimination, addressing limitations in analyzing complex molecular mixtures and subtle spectral variations.
• To introduce a novel air-liquid microfluidics-integrated SERS (ALM-SERS) system employing a sequential molecular adsorption strategy.
• To validate the ALM-SERS system's capability in differentiating bacterial species, including those with differing antibiotic resistance profiles.

Main Methods:

• Integration of microfluidics for precise microdroplet manipulation and controlled contact area with a SERS substrate.
• Implementation of a sequential molecular adsorption strategy to manage signal interference from complex purine derivative mixtures in bacterial supernatants.
• Evaluation of molecular affinities of purine derivatives and competitive adsorption using model mixtures (adenine/cytosine, hypoxanthine/uracil).

Main Results:

• The ALM-SERS system successfully performed sequential molecular adsorption, mitigating signal interference in complex mixtures.
• Proof-of-concept experiments demonstrated effective competitive analyte adsorption with model purine derivative mixtures.
• Testing on six bacterial supernatants and six clinically isolated samples showed the system's potential for discriminating between similar species with subtle spectral differences, even those with varying antibiotic resistance.

Conclusions:

• The developed ALM-SERS system provides a powerful platform for bacterial discrimination, excelling even with subtle spectral variations.
• The sequential molecular adsorption strategy effectively addresses signal interference, improving SERS analysis of complex biological samples.
• This technology holds significant promise for applications beyond microbiology, including drug development, food safety, and environmental monitoring.