Flexible nanohybrid substrates utilizing gold nanocubes/nano mica platelets with 3D lightning-rod effect for highly efficient bacterial biosensors based on surface-enhanced Raman scattering

• Published in: Journal of materials chemistry. B, Materials for biology and medicine Vol. 12; no. 13; pp. 3226 - 3239
• Main Authors: Chen, Yan-Feng, Lu, Ming-Chang, Lee, Chia-Jung, Chiu, Chih-Wei
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 27.03.2024
• Subjects: Adenine; Adsorption; Aluminum Silicates; Bacteria; Biological effects; Biomolecules; Biosensing Techniques; Biosensors; Copolymers; Diamines; E coli; Escherichia coli; Gold; Gold - chemistry; Hydrophilicity; Hydrophobicity; Lightning; Mica; Platelets; Polyoxyethylene; Raman spectra; Reproducibility of Results; Selectivity; Self-assembly; Spectrum Analysis, Raman - methods; Staphylococcus aureus; Substrates; Surface chemistry
• ISSN: 2050-750X; 2050-7518; 2050-7518
• DOI: 10.1039/d3tb02897f

In this study, gold nanocubes (AuNCs) were quickly synthesized using the seed-mediated growth method and reduced onto the surface of two-dimensional (2D) delaminated nano mica platelets (NMPs), enabling the development of AuNCs/NMPs nanohybrids with a 3D lightning-rod effect. First, the growth-solution amount can be changed to easily adjust the AuNCs average-particle size within a range of 30-70 nm. The use of the cationic surfactant cetyltrimethylammonium chloride as a protective agent allowed the surface of AuNCs and nanohybrids to be positively charged. Positively charged nanohybrid surfaces presented a good adsorption effect for detecting molecules with negative charges on the surface. Additionally, the NMP surfaces were rich in ionic charges and provided a large specific surface area for stabilizing the growth of AuNCs. Delaminated AuNCs/NMPs nanohybrids can generate a 3D hotspot effect through self-assembly to enhance the Raman signal. Surface-enhanced Raman scattering (SERS) is highly sensitive in detecting adenine biomolecules. Its limit of detection (LOD) and Raman enhancement factor reached 10 −9 M and 3.6 × 10 8 , respectively. Excellent reproducibility was obtained owing to the relatively regular arrangement of AuNC particles, and the relative standard deviation (RSD) was 10.7%. Finally, the surface of NMPs was modified by adding the hydrophilic poly(oxyethylene)-diamine (POE2000) and amphiphilic PIB-POE-PIB copolymer at different weight ratios. The adjustment of the surface hydrophilicity and hydrophobicity of AuNCs/NMPs nanohybrids led to better adsorption and selectivity for bacteria. AuNCs/POE/NMPs and AuNCs/PIB-POE-PIB/NMPs were further applied to the SERS detection of hydrophilic Staphylococcus aureus and hydrophobic Escherichia coli , respectively. The SERS-detection results suggest that the LOD of hydrophilic Staphylococcus aureus and hydrophobic Escherichia coli reached 92 CFU mL −1 and 1.6 × 10 2 CFU mL −1 , respectively. The AuNCs/POE/NMPs and AuNCs/PIB-POE-PIB/NMPs nanohybrids had different hydrophilic-hydrophobic affinities, which greatly improved the selectivity and sensitivity for detecting bacteria with different hydrophilicity and hydrophobicity. Therefore, fast, highly selective, and highly sensitive SERS biological-detection results were obtained. Rapid synthesis of gold nanocubes (AuNCs)/two-dimensional delaminated nano mica platelets (NMPs), controlling surface hydrophilic-hydrophobic properties for the SERS detection of different bacteria.