Porous Silicon-Based Optical Biosensors and Sensing Technologies

Porous silicon (PSi) has emerged as a versatile platform for optical biosensing, combining a high internal surface area with tunable refractive index and photonic properties. Fabricated by electrochemical etching of crystalline silicon, PSi films can be engineered into Fabry–Pérot interferometers, microcavities or one-dimensional photonic crystals, whose optical response shifts in the presence of target analytes. Such shifts arise from changes in effective refractive index or photoluminescence signals and enable label-free, real-time detection. Surface functionalisation strategies—ranging from silane chemistry to layer-by-layer assembly of polyelectrolytes—permit immobilisation of bioreceptors including antibodies, aptamers and lectins. Integration with microfluidic architectures and in-situ monitoring techniques has addressed mass-transport limitations and improved sensitivity. Practical applications span clinical diagnostics, food-safety testing, environmental monitoring and biosecurity, where PSi sensors have demonstrated detection limits down to the femtomolar range for proteins and down to 10^3–10^4 cells mL⁻¹ for bacteria.

Research from Nature Portfolio

Advances in surface biofunctionalisation have enabled robust affinity biosensing on PSi interferometers through electrostatic layer-by-layer nano-assembly of oppositely charged polyelectrolytes bearing bioreceptors. This approach has achieved sub-picomolar detection of streptavidin in complex media with high selectivity and stability. Complementary work has demonstrated fabrication of one-dimensional PSi photonic crystals by electrochemical etching monitored in real time via photoacoustic signals. In-situ feedback on refractive index, porosity and roughness has yielded photonic structures with narrow, well-resolved optical features suitable for sensitive optical transduction. In parallel, lectin-conjugated mesoporous PSi films have been shown to detect Gram-positive and Gram-negative bacteria in real time, exploiting the carbohydrate-binding specificity of concanavalin A and wheat germ agglutinin to deliver limits of detection around 10³ cells mL⁻¹ and to discriminate bacterial classes without secondary labelling.

Porous Silicon-Based Optical Biosensors and Sensing Technologies publication trend

The graph below shows the total number of articles in porous silicon-based optical biosensors and sensing technologies across all publications each year (not limited to Nature Index journals).

Technical terms

Porous silicon (PSi): A nanostructured form of silicon with interconnected pores formed by electrochemical etching, providing high surface area and tunable optical properties.

Fabry–Pérot thin film: An optical cavity composed of two parallel reflective surfaces; in PSi sensors, interference fringes shift in wavelength upon refractive index changes.

Photonic crystal: A periodic optical nanostructure that creates photonic bandgaps, producing sharp reflectivity features for enhanced sensing sensitivity.

Layer-by-layer assembly: A sequential deposition technique for constructing multilayer films via alternating adsorption of oppositely charged polymers or particles.

Lectin: A carbohydrate-binding protein used as a bioreceptor for selective capture of bacterial cell-surface glycans.

Aptamer: A short single-stranded DNA or RNA sequence engineered to bind a specific target molecule with high affinity.

Microfluidic integration: Incorporation of microscale channels and mixers to enhance convective transport and reduce mass-transport limitations within the sensor.

References

1. Enhancing the performance of porous silicon biosensors: the interplay of nanostructure design and microfluidic integration. Microsystems & Nanoengineering (2024).
2. Design of a Porous Silicon Biosensor: Characterization, Modeling, and Application to the Indirect Detection of Bacteria. Biosensors (2024).
3. Layer-by-layer biofunctionalization of nanostructured porous silicon for high-sensitivity and high-selectivity label-free affinity biosensing. Nature Communications (2018).
4. Design, fabrication, and optical characterization of one-dimensional photonic crystals based on porous silicon assisted by in-situ photoacoustics. Scientific Reports (2019).
5. A lectin-coupled porous silicon-based biosensor: label-free optical detection of bacteria in a real-time mode. Scientific Reports (2020).
6. Mass Transfer Limitations of Porous Silicon-Based Biosensors for Protein Detection. ACS Sensors (2020).