Quantitative age grading of mosquitoes using surface-enhanced Raman spectroscopy

Area of Science:

• Analytical Chemistry
• Vector Biology
• Spectroscopy

Background:

• Mosquito-borne diseases (malaria, Zika, dengue, chikungunya) pose a significant global health threat.
• Accurate mosquito age-grading is crucial for epidemiological studies, as older female mosquitoes are more infectious.
• Current methods for determining mosquito age are lacking in reliability, cost-effectiveness, and practicality.

Purpose of the Study:

• To develop and validate a novel surface-enhanced Raman spectroscopic (SERS) method for mosquito age-grading.
• To identify the biological components responsible for spectral changes during mosquito aging.
• To assess the impact of pathogen deactivation pre-treatments on the SERS method's efficacy.

Main Methods:

• Water extracts of Aedes aegypti mosquitoes (0-22 days old) were analyzed using SERS with silver nanoparticles.
• Spectra were analyzed using principal component analysis (PCA) and partial least squares (PLS) regression.
• Infrared spectroscopy was used to identify spectral contributors; pre-treatments (bleach, ethanol) were evaluated.

Main Results:

• The SERS method accurately predicted mosquito age (0-22 days) with high correlation coefficients (R=0.994 for calibration, R=0.990 for validation).
• Adenine-containing compounds and proteins were identified as key biological factors influencing spectral changes for age determination.
• Ethanol pre-treatment enhanced the SERS method's discrimination capability and improved safety.

Conclusions:

• Surface-enhanced Raman spectroscopy offers a promising, rapid, and reliable method for grading mosquito age.
• This technique can be developed into a field-deployable tool for enhanced vector-borne disease surveillance.
• The findings contribute to improved strategies for monitoring and preventing the spread of mosquito-borne illnesses.