Hierarchical Assembly of Flexible Biopolymer Polyphosphate-Manganese into Nanosheets.

Polyphosphate (polyP) is one of the most compact inorganic polyanionic biopolymers that participates in various physiological processes. However, the development of polyP-based nanomaterials is still in its infancy. Here, biocompatible polyphosphate-manganese nanosheets are designed and synthesized by a hierarchical assembly strategy. The thickness and the lateral size of the resulting polyP-Mn nanosheets (PMNSs) are 5 nm and 120-130 nm, respectively. Molecular dynamics simulations suggested that the polyP-hexadecyl trimethyl ammonium bromide flat structure possesses a strong aggregating capacity and serves as the template for the 2D assembly of polyP-Mn. The PMNSs can activate the inflammatory response of macrophages resulting in the recovery of innate immunological functions to inhibit tumor proliferation. This work has initiated a new direction in constructing layered polyP-based nanomaterials and provides guidance for biocompatible and biodegradable biopolymer-based materials in the regulation of innate responses.

A novel fluorescence method for detection of phosphate anions based on porphyrin metalation.

In this work, a novel fluorescence method for the detection of phosphate anions (PO43-) was developed based on porphyrin metalation. Through catalysis by G-quadruplex (G4), Cu2+ could insert into the porphyrins to quench their fluorescence. G4 simultaneously improved the fluorescence of the porphyrins but not that of Cu2+-porphyrin. In the absence of PO43-, the porphyrins were metallized by Cu2+, and no fluorescence was observed. In the presence of PO43-, PO43- could coordinate with Cu2+ to prevent porphyrin metalation. Free porphyrin could bind with G4 to emit strong fluorescence. By comparing four common porphyrins, we found that G4 had the greatest effect on increasing the fluorescence intensity of N-methylmesoporphyrin IX (NMM). Thus, NMM/G4 was chosen for the design of a biosensor. Under optimal experimental conditions, this method showed high sensitivity and satisfactory selectivity for PO43- with a detection limit of 44 nM in a linear range of 0.01-1.0 µM. The recovery experiments showed recovery rates of 93.75-106.00%, suggesting a great potential for measuring PO43- in real samples.