Protein Adsorption on Mixed Self-Assembled Monolayers: Influence of Chain Length and Terminal Group

Area of Science:

• Surface Science
• Biomaterials Engineering
• Nanotechnology

Background:

• Mixed self-assembled monolayers (SAMs) offer tunable properties for biosensing.
• Molecular disorder is common in mixed SAMs, especially with differing thiol components.
• Understanding protein adsorption on mixed SAMs is crucial for optimizing biosensor performance.

Purpose of the Study:

• To investigate how mixed SAM structure influences bovine serum albumin (BSA) physisorption.
• To determine the effect of mixing ratio and thiol chain length on protein adsorption.
• To assess the predictability of BSA adsorption based on SAM composition.

Main Methods:

• Fabrication of mixed SAMs with varying ratios of hydroxyl (-OH) and methyl (-CH3) terminated thiols.
• Analysis of SAM structure and protein adsorption using techniques suitable for polycrystalline substrates.
• Quantification of BSA adsorption under varying SAM compositions and chain lengths.

Main Results:

• BSA adsorption is predictable by mixing ratio when methyl-terminated thiols constitute ≥50% of the SAM.
• This predictability holds regardless of chain length differences, except for specific cases with longer methyl-terminated thiols at low ratios.
• Protein adsorption increases on disordered SAMs with exposed alkane backbones at low methyl-terminated ratios.

Conclusions:

• SAM mixing ratio is a key determinant of BSA adsorption, particularly above 50% methyl-terminated groups.
• While molecular disorder exists, varying thiol chain lengths have a limited impact on overall protein adsorption behavior.
• Mixed SAMs remain highly tunable for biosensing applications, with composition being a primary control factor.