Revealing the Phagosomal pH Regulation and Inflammation of Macrophages after Endocytosing Polyurethane Nanoparticles by A Ratiometric pH Nanosensor.

The effect of the intracellular pH of macrophages after taking up biodegradable polymer nanoparticles (NPs) on immunomodulating functions has not been explored so far. Previous studies have demonstrated that biodegradable polyurethane (PU) NPs exhibit immunosuppressive activity. Yet, the intracellular mechanism is not clearly understood. In this study, a uniquely designed pH nanosensor is employed for tracking the intracellular pH value of macrophages to reveal the intracellular journey of PU NPs and to clarify the intracellular pH effect on the corresponding inflammatory response. First, fluorescent mesoporous silica nanoparticles (FRMSNs) is used to detect the pH change in macrophages after endo/phagocytosis of PU NPs. Second, PU is coated on the external surface of FRMSNs to examine the intracellular trafficking process of PU in the macrophages. The results show that the majority of PU-coated FRMSNs remain to stay at the cytosol-early endosome/phagosome regions. The intracellular pH value and other supporting results show that the immune response of PU NPs may be correlated to their internalization journey. The retardation in the degradation process of the PU NPs may intervene with the lysosome activity and repress the immunostimulatory effect, which contributes to the low immune response of PU NPs.

Sub-attomolar electrochemical measurement of DNA hybridization based on the detection of high coverage biobarcode latex labels at PNA-modified screen printed electrodes.

We have constructed biobarcode labels based on 468nm diameter latex spheres. Modification with polyallylamine and then glutaraldehyde was used to attach a high DNA loading, consisting of aminated probe DNA (approx. 1.01×102 molecules per sphere) and biobarcode DNA (approx. 1.66×104 molecules per sphere). Detection of the biobarcodes was performed by application of a Ag enhancer solution, causing association of the Ag+ ions with the phosphate groups of the DNA. The deposited Ag was detected by differential pulse voltammetry. A 30 mer sequence from the BL21 strain of E. coli was detected with an LOD of 2.6fM (calibration range 10 aM to 0.1pM, r2=0.91, n=45). The LOD was lowered to 0.56aM (calibration range 100zM to 0.1nM, r2=0.991, n=50) by utilizing a sandwich assay with PNA-modified screen printed electrodes, which lowered the Ag background current. The sandwich assay platform was used to calibrate E. coli strain BL2(DE3) with an LOD of 17.0 CFU mL-1 (calibration range 10 to 106 CFU mL-1, r2=0.99, n=33) with good discrimination against Salmonella.