Diagnosis of viral infectious diseases through sensitive detection of human serum antibodies using a modified label-free electrochemical biosensor.

Rapid virus identification is crucial for preventing outbreaks. The COVID-19 pandemic has highlighted the critical nature of rapid virus detection. Here, we designed a label-free electrochemical biosensor modified with gold nanoparticles (AuNPs) to detect IgG antibodies from human serum, enabling rapid point-of-care diagnostics. AuNPs were synthesized and characterized. A multivariate optimization was carried out to determine the optimal condition for functionalizing AuNPs with anti-IgG. Subsequently, using a glassy carbon electrode (GCE), a modified AuNPs/GCE electrochemical biosensor was developed for IgG detection. The results indicated that AuNPs displayed a spherical morphology with a size distribution of 19.54 nm. Additionally, the zeta potential was recorded at -7.84 mV. Central composite design (CCD) analysis determined the optimal conditions for functionalizing AuNPs to be an anti-IgG concentration of 320 µg mL-1, a temperature of 25 °C, and pH of 7.4. The characterization study confirmed the successful synthesis and functionalization of AuNPs. Through electrochemical impedance spectroscopy measurement, the biosensor demonstrated a limit of detection (LOD) of 0.2 ng mL-1 and limit of quantification (LOQ) of 0.8 ng mL-1. Furthermore, tests in real samples showed the interaction between IgG antibodies in serum samples and AuNPs/GCE, confirming the biosensor's ability to detect and quantify IgG in clinical samples.

Molecularly imprinted polymer as sorbent phase for disposable pipette extraction: A potential approach for creatinine analysis in human urine samples.

Traditionally, creatinine determination is made by a spectrophotometric method; however, some compounds present in biological samples can interfere with creatinine determination, decreasing the sensitivity of the method in urine samples. Consequently, we report the development of a new molecularly imprinted polymer as a sorbent phase for disposable pipette extraction to determine creatinine in urine samples by high-performance liquid chromatography with UV detection. The synthesized polymer showed a high superficial area and presented a first-order kinetic reaction and a high selectivity for creatinine extraction compared to the non-molecularly imprinted polymer. The main disposable pipette extraction variables evaluated included the number of draw/eject cycles, the pH of the solution and desorption solvent type. The developed method showed an inter and intra-day precision from 1.3% to 2.0% and 0.8-1.6% respectively, accuracy values ranging from 82.3% to 102.1% respectively and recovery values ranging between 96.5% and 101.3%, with a limit of quantification of 0.302 g L-1. The application of the developed method in real urine samples showed creatinine concentrations ranging from 0.55 to 6.61 g L-1. Thus, the developed method was revealed to be an efficient strategy for creatinine determination, reducing analysis time (3 min) and solvent use, and increasing selectivity compared with DPX commercial sorbents.