Milli q ultrapure water machine

The UV-vis absorption spectra were recorded on a UV-2450 spectrophotometer (Shimadzu, Japan). X-ray photoelectron spectroscopy (XPS) was recorded on a VG Multilab 2000 X-ray photoelectron spectrometer (Thermo VG, UK). Fluorescence measurements were performed using an RF-5301 PC spectrofluorometer (Shimadzu, Japan). Fourier transform infrared spectra (FTIR) were obtained to identify the molecular structures of Au NCs with a Nicolet Avatar-330 spectrometer (Thermo Nicolet, USA) through the KBr pellet technique. The size and morphology of Au NCs were recorded on a HRTEM JEM-2100F instrument (JEOL, Japan). All deionized water was obtained from a Milli-Q ultrapure water machine (Millipore, USA).

Dried Radix of P. chinensis was purchased from a Chinese herbal medicine store in Suzhou and identified by Prof. Xiaoran Li of the School of pharmacy of Suzhou University. The voucher specimen (No. 08-02-15-18) has been deposited at Soochow University. The other materials used in the study were bought from different companies as follows; Salicylazosulfapyridine (SASP) from (Shanghai Xinyi Tianping Pharmaceutical Co., Ltd., gyzz H31020557); CMC-Na (Carboxymethylcellulose sodium) (Xilong Chemical Co., Ltd.), Dextran sulfate sodium (DSS) from (MP Biomedical, LLC); chloral hydrate, and paraformaldehyde from (Shanghai Aladdin Biochemical Technology Co., Ltd.); KQ-250DB numerical control ultrasonic cleaner from (Gongyi Yuhua Instrument Co., Ltd.); Milli-Q ultrapure water machine from (Millipore company); 4°C refrigerator from (Haier company); –80°C ultra-low temperature refrigerator from (Thermo Fisher company); KDM type temperature control electric heating set from (juancheng Hualu electric heating instrument Co., Ltd.); SY-2000 rotary evaporator from (Shanghai Yarong biochemical instrument factory); SHB-III circulating water multi-purpose vacuum pump from (Zhengzhou Great Wall Technology Industry and Trade Co., Ltd.); and Doppler infrared imager from (Model: MOORLDI2-HIR, Moor Instruments Ltd Millwey Rise, AXMINSTER DEVON, EX13 5HU UK).

All antimicrobial drug standards (≥97% purities) were obtained from Alta (Tianjin, China). MS-grade methanol, acetonitrile, formic acid (FA), ammonium formate, and HPLC-grade toluene were obtained from Fisher (Branchburg, NJ, USA). Analytical grade anhydrous Na₂SO₄, anhydrous MgSO₄, trisodium citrate, disodium citrate, sodium chloride (NaCl), and sodium acetate (NaOAc) were purchased from Beijing Chemical Plant (Beijing, China); A bonded C18 zirconia-coated silica (Z-Sep⁺) was obtained from Sigma (Osterode am Harz, Germany). Primary secondary amine (PSA) and octadecyl silane (C18) were obtained from Agilent Technologies (Santa Clara, CA, USA). Ultra-pure water was prepared by Milli-Q ultrapure water machine obtained from Millipore Corporation (Burlington, MA, USA).
Forty-three antimicrobial drug standards are listed in Table S1, including quinolones and sulfonamides. Usually, individual stock solutions of drugs were prepared in methanol or acetonitrile at 500−1000 mg/L concentrations. All stock solutions could be stored stably for six months in closed brown-colored volumetric flasks under −20 °C refrigeration conditions. The standard working solution was diluted with methanol to the desired concentration (stored at −20 °C and prepared once a month).