Tuning the Photothermal Effect of Carboxylated-Coated Silver Nanoparticles through pH-Induced Reversible Aggregation

Progress in the preparation of Prussian blue-based nanomaterials for biomedical applications

Prussian blue (PB) is composed of the coordination network of Fe²⁺-CN-Fe³⁺ mixed valence state as a classic metal complex, which includes a C atom and Fe²⁺ (low spin), N atom and Fe³⁺ (high spin). PB and its analogues (PBA) have excellent biosafety, good magnetic properties, outstanding photothermal properties and the ability to mimic enzymatic behaviors due to their stable structure, tunable size, controllable morphology, abundant modification methods and excellent physicochemical properties. They have received increasing research interest and have shown promising applications in the biomedical field. Here, progress in the preparation of PB-based nanomaterials for biomedical applications is summarized and discussed. The preparation strategies, traditional synthesis and emerging preparation methods of PB are summarized systematically in this review. The design and preparation of PBA, PB(PBA)-based hollow structures and PB(PBA)-based composites are also included. While introducing the preparation status, some PB-based nanomaterials that have performed well in specific biomedical fields are emphasized. More importantly, the key factors and future development of PB for the clinical translation as multifunctional nanomaterials are also discussed. This review provides a reference for the design and biomedical application of PB-based nanomaterials.

Poly(N-isopropylacrylamide)-interpenetrated chitosan coils working as nanoreactors for controlled silver nanoparticle growth

A new precursor (Ag⁺/CS/PNIPA) arranged as a nanogel (nanoreactor) is obtained from the aqueous mixture of Ag⁺, chitosan (CS) and poly(N-isopropylacrylamide) (PNIPA). A model synthetic system based on the thermally induced aqueous silver ions-CS reaction to form silver nanoparticles (AgNP) is used as a starting point to assess the PNIPA role as a thermo-sensitive additive of synthesis in a low content for the production of size-controlled AgNP. As expected, the PNIPA phase transition produced by the temperature increase leads to chitosan nanogel contraction, lowering the diffusion of ionic species. PNIPA behaves as a successful additive between 5.6 and 10.5 wt% of content blended with chitosan, noticeably improving AgNP nucleation during thermal treatment at 90 °C. Higher PNIPA contents are less effective in achieving size control and broader size distributions are generated. The PNIPA effect on the nanoreactor structure is characterized by rheology, modelled and analyzed against the AgNP morphology obtained.