Study on Physio-chemical Properties of plasma polymerization in C2H2/N2 plasma and Their Impact on COL X

Protein ion yield enhancement in matrix-assisted laser desorption/ionization mass spectrometry after sample and matrix low-pressure glow discharge plasma irradiation

RATIONALE

Plasma-assisted ionization is widely used in mass spectrometry; in this study, a low-pressure glow discharge is introduced as a new method to improve the detection of large proteins, and bovine serum albumin (BSA) is used as a protein model. The treatment of analyte, matrix, and the matrix/analyte mixture is evaluated under optimal conditions.

METHODS

Low-pressure radio-frequency capacitively coupled plasma (RF-CCP) treatment is utilized in the sample preparation step of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to enhance the protein MALDI ion signal. Plasma treatment can be an effective tool for enhancing the non-covalent binding of the analyte with the matrix, incorporation of the analyte into the matrix, production of matrix/analyte crystals, and analyte protonation through plasma activation, resulting in an improved MALDI ion signal.

RESULTS

Fourier-transform infrared (FTIR) spectroscopy allows us to distinguish between the functional groups of plasma-treated and control samples. In addition, optical emission spectroscopy (OES) determines the plasma species, and zeta potential analysis characterizes the potential difference between plasma-treated and control samples before MALDI-TOF MS analysis. Plasma-treated BSA can provide a five-times enhancement of ion intensity. The combination of the plasma-treated analyte with the plasma-treated matrix leads to an increase in the ion intensity by a factor of 14.

CONCLUSIONS

Low-pressure glow discharge plasma treatment greatly enhances MALDI ion signals, with a noticeable increase in incorporation, co-crystallization, protonation, and the concentration of the sample functional groups.

Effect of Functional Groups of Self-Assembled Monolayers on Protein Adsorption and Initial Cell Adhesion

Surface modification plays a vital role in regulating protein adsorption and subsequently cell adhesion. In the present work, we prepared nanoscaled modified surfaces using silanization and characterized them using Fourier-transform infrared spectroscopy (FTIR), water contact angle (WCA), and atomic force microscopy (AFM). Five different (amine, octyl, mixed, hybrid, and COOH) surfaces were prepared based on their functionality and varying wettability and their effect on protein adsorption and initial cell adhesion was investigated. AFM analysis revealed nanoscale roughness on all modified surfaces. Fetal bovine serum (FBS) was used for protein adsorption experiment and effect of FBS was analyzed on initial cell adhesion kinetics (up to 6 h) under three different experimental conditions: (a) with FBS in media, (b) with preadsorbed FBS on surfaces, and (c) incomplete media, i.e., without FBS. Various cell features such as cell morphology/circularity, cell area and nuclei size were also studied for the above stated conditions at different time intervals. The cell adhesion rate as well as cell spread area were highest in the case of surfaces with preadsorbed FBS. We observed higher surface coverage rate by adhering cells on hybrid (rate, 0.073 h^-1) and amine (0.072 h^-1) surfaces followed by COOH (0.062 h^-1) and other surfaces under preadsorbed FBS condition. Surface treated with cells in incomplete media exhibited least adhesion rate, poor cell spreading and improper morphology. Furthermore, we found that initial cell adhesion rate and Δadhered cells (%) linearly increased with the change in α-helix content of adsorbed FBS on surfaces. Among all the modified surfaces and under all three experimental conditions, hybrid surface exhibited excellent properties for supporting cell adhesion and growth and hence can be potentially used as surface modifiers in biomedical applications to design biocompatible surfaces.