Multifunctional Metal Oxide Nanomaterials For Metabolite Detection By Laser Desorption/Ionization Mass Spectrometry And Suitable Strategy For Phosphopeptides Detection Using Electrochemical Techniques

Metabolic analysis provides answers in the diagnosis of many inherited diseases by sensitive and accurate quantification of molecules ranging from carbohydrates,amino acids,lipids and peptides.Considering the importance of diagnosis in the management of metabolic diseases,development of novel diagnostics methods are in urgent need.Over the past decades,the rapid development of nanotechnology has provided new insight into future diagnostic approaches.Especially,the design of core/shell nano-composites with unique surface chemistries attract attention in the metabolite analysis as LDI MS matrix.This promising approach to detect/quantify the low molecular weight molecules(<600 m/z)by nano/micro inorganic materials as a matrix is in serious demand.However,the application of these materials is very limited in real biological samples,owing to high sample complexity and low molecular abundance.Herein,we report a new metal oxide nanomaterial(SiO2-NH2@ZrO2)matrix for analysis of low-molecular weight compounds using laser desorption/Ionization mass spectrometry(LDI MS).The use of zirconia-silica coating(SiO2-NH2@ZrO2)avoided the fragmentation of analytes and provided good reproducibility and high salt tolerance property,highlighting the potential applications in complex biosample.We further utilized this SiO2-NH2@ZrO2 material as a novel electrochemical sensor for detection of phosphopeptides by electrochemistry technique.In this method,metal oxide nanomaterials were electrodeposited on a glassy indium tin oxide(ITO)electrode to saturation can be replaced by the non-electroactive P-peptides by competing the binding sites on affinity metal oxide,resulting in a decrease of peak current of non-phosphopeptides/metal oxide deposited electrode.It was successfully fabricated on the indium tin oxide(ITO)electrode using differential pulse voltammetry(DPV)and cyclic voltammetry(CV).The change of peak current directly related to the concentration of the P-peptides in solution,and thus,P-peptides can be quantitatively determined.The SiO2-NH2@ZrO2 fabricated film was successfully employed for the detection of Phosphopeptides(p-peptides)in real biosamples.The results revealed decreased peak current is linear proportional to the logarithm of the concentration of P-peptides from 0.01 ng/mL to 1000 ng/mL with a detection limit of 78.6 pg/mL(S/N=3).Overall,we developed an optimized SiO2-NH2@ZrO2 matrix for LDI MS analysis of small molecules in human serum samples.Notably,the LDI MS based on SiO2-NH2@ZrO2 was advantageous due to easy sample preparation,low sample consumption and high speed of analysis.At the same time,we utilized optimized SiO2-NH2@ZrO2 particles for detection of phosphopeptides by electrochemical sensing.Our works not only widen the use of inorganic materials in LDI MS,but also promoted the practical application of novel noble metal oxides in electrochemical analysis.