Colorimetric detection of glucose using enzyme-mimic nanoparticles (NPs) has been drawing great attention. However, many NPs lack good stability in solution, which results in reduced color change of substrates in colorimetric detection. Liner soluble macromolecules with high cationic density may be suitable candidates for the stabilization of NPs. Herein, we prepared polyethyleneimine-stabilized platinum NPs (Pt_n-PEI NPs) for colorimetric detection of glucose. The platinum NPs (Pt NPs) used in this system had small size (from 3.21 to 3.70 nm) and narrow size distribution. Pt₅₀-PEI NPs had high stability within one week with a hydrodynamic size of ∼25 nm and slightly positive zeta potential. Pt₅₀-PEI NPs-catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H₂O₂, generating blue oxidized TMB (oxTMB), which indicated the peroxidase-like property of Pt₅₀-PEI NPs. The optimal condition for this reaction was pH = 4.0 at 30 °C. More importantly, Pt₅₀-PEI NPs were successfully used to detect glucose concentration by a colorimetric method with high selectivity. The established method had a linear concentration range from 10 to 5000 μM with a detection limit of 4.2 μM. For example, the concentration of glucose in saliva was tested to be 0.15 mM using our method. The high stability of Pt₅₀-PEI NPs enhanced the high accessibility of the active center of Pt NPs for substrates and consequent excellent catalytic property. This established method has great potential to be used in various applications for glucose detection in the future.

The development of stable and biocompatible gold nanoparticles has been drawing great interest. Dendrimers could be used as templates to entrap gold nanoparticles. Herein, dendrimer templates were prepared by the modification of generation 5 polyamidoamine (G5 PAMAM) dendrimers with maleic anhydride and cysteamine. Then modified dendrimer-encapsulated gold nanoparticles (Au-G5MC NPs) were formed by incubation of the templates with chloroauric acid and reduction with sodium borohydride. The resulting Au-G5MC NPs showed high stability, biocompatibility, and catalytic efficiency in water, which is ascribed to the single zwitterionic layer composed of amine and carboxyl groups. The single zwitterionic layer was shown to provide the Au-G5MC NPs with excellent stability in both phosphate-buffered saline and fibrinogen solutions. The mixed solution of Au-G5MC NPs with fibrinogen remained stable within 24 h, while the mixed solution of G5 PAMAM dendrimer-entrapped gold nanoparticles (Au-G5 NPs) with fibrinogen formed obvious aggregates immediately. Au-G5MC NPs displayed little cytotoxicity (>90% cell viability) against HeLa cells up to 100 μg mL⁻¹, while Au-G5 NPs showed obvious cytotoxicity (60% cell viability). In addition, Au-G5MC NPs displayed high catalytic efficiency for the reduction reaction of 4-nitrophenol (4-NP) in water. This method can be used to prepare a variety of highly stable, biocompatible, and efficient dendrimer-encapsulated catalysts.

Bovine serum albumin stabilized platinum nanoparticles promoted the formation of ˙OH from H₂O₂to catalyze the oxidation of morin.