In a recent article published in the journal Microsystems & Nanoengineering, researchers focused on enhancing biosensing capabilities by utilizing focused traveling surface acoustic waves in an acoustic microfluidic chip.
Traditional biosensors face limitations in achieving high sensitivity and speed due to passive diffusion of target molecules. The need for selective enrichment strategies to improve detection sensitivity and speed is highlighted.
a Detailed detection process (i) and the x-z plane (ii) and y-z plane (iii) show enrichment. b Microscope images of the captured 7 µm microbeads at concentrations of 0 (i), 10 ng/mL (ii), and 100 pg/mL (iii). Image Credit: https://www.nature.com/articles/s41378-024-00731-3
Background
The development of sensitive and rapid biosensing technologies is crucial for various applications in clinical diagnostics and scientific research. Traditional biosensors often face challenges related to the passive diffusion of target molecules, leading to inefficiencies in capturing and detecting rare molecules with high precision. This limitation results in prolonged incubation times and potential false-negative results, particularly at low concentrations of target molecules.
To address these challenges, there is a growing need for innovative biosensing methods that can enhance both sensitivity and speed of detection. The integration of acoustofluidics, which involves the manipulation of fluids and particles using acoustic waves, presents a promising approach to improve biomolecular detection capabilities.
By leveraging focused traveling surface acoustic waves within microfluidic devices, researchers can achieve continuous enrichment of target molecules in specific detection zones, leading to rapid and efficient biosensing.
The Current Study
The experimental setup involved the fabrication and integration of an acoustic microfluidic chip with a focused interdigital transducer (FIDT) to enable efficient capture and detection of microbeads pre-captured with target molecules. The chip design included microchannels for fluid flow and a constriction zone for specific enrichment and detection.
To prepare the chip, polydimethylsiloxane (PDMS) was used for molding the microchannels, while the FIDT was fabricated using standard lithography techniques. The FIDT was crucial for generating focused traveling surface acoustic waves (FTSAWs) within the chip, which played a key role in enriching the target molecules.
For the biomolecular enrichment process, polystyrene microbeads were functionalized with human IgG molecules at varying concentrations (100, 10, 1, and 0.1 ng/mL) and introduced into the microfluidic chip. The microbeads were guided through the microchannels towards the constriction zone using the acoustic force generated by the FTSAWs.
ImageJ software was utilized to analyze and count the enriched microbeads in the constriction zone. The number of microbeads captured at different concentrations of human IgG molecules was recorded to assess the detection performance of the system. The detection time and concentration capability were determined based on the experimental results.
Furthermore, surface modifications were carried out on the top surface of the microchannels using 3-aminopropyl triethoxysilane and glutaraldehyde aqueous solutions to facilitate biomolecular binding. Human IgG, anti-human IgG FITC, and goat anti-human IgG (Fab specific) were employed for biomolecular enrichment and detection processes.
Results and Discussion
The experimental results demonstrated the effectiveness of the acoustofluidics-enhanced biosensing method in achieving rapid and highly sensitive detection of target molecules. The biosensing times for different molecular concentrations (100, 10, 1, and 0.1 ng/mL) were recorded, showing a clear trend of decreasing detection time with increasing concentration.
This indicated the ability of the system to detect lower concentrations of target molecules with shorter detection times, highlighting the high sensitivity of the method.
Moreover, the number of enriched microbeads at 60 seconds for each molecular concentration provided valuable insights into the enrichment efficiency of the system. The results showed a significant increase in the number of enriched microbeads with higher molecular concentrations, further confirming the system's capability to capture and enrich target molecules effectively.
The potential limit of detection (LOD) of the device was estimated to be lower than 100 pg/mL based on the experimental data, emphasizing the high sensitivity of the acoustofluidics-enhanced biosensing method. This low LOD indicates the system's ability to detect trace amounts of target molecules, making it suitable for applications requiring detection of rare molecules with high precision.
The integration of a sandwiching biosensing method using anti-human IgG FITC and goat anti-human IgG (Fab specific) further enhanced the specificity of the detection process. By surface-modifying the microchannel and microbeads with specific antibodies, the system achieved improved selectivity in capturing target molecules, reducing the likelihood of false-positive results.
Conclusion
In conclusion, the study successfully showcased the effectiveness of acoustofluidics-enhanced biosensing in achieving high sensitivity and detection speed. By leveraging focused traveling surface acoustic waves and selective enrichment strategies, the method outperformed traditional biosensors in terms of sensitivity and speed.
The findings emphasize the importance of innovative approaches in biosensing technologies to enhance detection capabilities for various applications in clinical and scientific settings.
Journal Reference
Li Y., Zhao Y., et al. (2024). Acoustofluidics-enhanced biosensing with simultaneously high sensitivity and speed. Microsystems & Nanoengineering 10, 92. DOI: 10.1038/s41378-024-00731-3, https://www.nature.com/articles/s41378-024-00731-3