Facile one-pot synthesis of multifunctional tetracycline hydrochloride nanoparticles with high stability and photothermal effect for synergistically improved antibacterial performance and sustainability

Tetracycline hydrochloride (TC) is a widely applied antibiotic. However, its instability requires overdose upon practical application, which raises the risk for the evolution of superbacteria. The solution to this matter lies in reducing the dosage of TC while maintaining its efficacy, which can be solved from two ways: 1) increasing the stability of TC; 2) improving the antibacterial ability of TC. Here in this study, with the aim to improve the stability of TC while with additional antibacterial ability, TC was assembled with ferric ion and polyvinylpyrrolidone (PVP) into TC multifunctional nanoparticles (TCFNPs). The Box-Behnken Design (BBD) was firstly introduced to recognize the crucial formulation variables on the influencing of particle size of TCFNPs. Under the optimized condition, TCFNPs with size of 9.95 nm can be obtained and showed high storage stability. The as-prepared TCFNPs not only showed comparable chemotherapeutic effects to free TC on both Gram-positive strain (Staphylococcus aureus, S. aureus) and Gram-negative strain of (Escherichia coli, E. coli), but also showed improved stability under room temperature upon light irradiation. Moreover, TCFNPs also exert photothermal effects which can synergistically provide enhanced antibacterial performance due to the combination of chemotherapy and photothermal therapy. Therefore, our study represents a new way to reform antibiotics with better stability and additional antibacterial ability for the better application of traditional antibacterial in agriculture.