Ruoyu Cheng: Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Helsinki FI-00014, Finland.
Shiqi Wang: Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Helsinki FI-00014, Finland.
Karina Moslova: Department of Chemistry, Faculty of Science, University of Helsinki, Helsinki FI-00014, Finland.
Ermei Mäkilä: Laboratory of Industrial Physics, Department of Physics and Astronomy, University of Turku, Turku FI-20014, Finland. ORCID
Jarno Salonen: Laboratory of Industrial Physics, Department of Physics and Astronomy, University of Turku, Turku FI-20014, Finland. ORCID
Jiachen Li: Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Helsinki FI-00014, Finland.
Jouni Hirvonen: Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Helsinki FI-00014, Finland.
Bing Xia: College of Science Key Laboratory of Forest Genetics & Biotechnology (Ministry of Education of China), Nanjing Forestry University, Nanjing 210037, P. R. China. ORCID
Hélder A Santos: Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Helsinki FI-00014, Finland. ORCID
Porous silicon (PSi) nanoparticles have been applied in various fields, such as catalysis, imaging, and biomedical applications, because of their large specific surface area, easily modifiable surface chemistry, biocompatibility, and biodegradability. For biomedical applications, it is important to precisely control the surface modification of PSi-based materials and quantify the functionalization density, which determines the nanoparticle's behavior in the biological system. Therefore, we propose here an optimized solution to quantify the functionalization groups on PSi, based on the nuclear magnetic resonance (NMR) method by combining the hydrolysis with standard H NMR experiments. We optimized the hydrolysis conditions to degrade the PSi, providing mobility to the molecules for NMR detection. The NMR parameters were also optimized by relaxation delay and the number of scans to provide reliable NMR spectra. With an internal standard, we quantitatively analyzed the surficial amine groups and their sequential modification of polyethylene glycol. Our investigation provides a reliable, fast, and straightforward method in quantitative analysis of the surficial modification characterization of PSi requiring a small amount of sample.
