Bacterial infection has become a serious clinical concern due to the emergence of drug-resistance and biofilm formation. Therefore, it is in great demand to develop efficient antimicrobial agents to treat bacterial infection without using antibiotics. Herein, we successfully prepared four quaternized ammonium PEI (QPEI: PEI1200-C2, PEI1200-C4, PEI1200-C6 and PEI1200-C8) using the commercial available PEI1200. Both PEI and four QPEI presented broad-spectrum antimicrobial activity against Gram-negative bacteria (E. coli, and P. aeruginosa) and Gram-positive bacteria (B. amyloliquefaciens and S. aureus), especially PEI1200-C6 showed the strongest antimicrobial activity with good biocompatibility at the MIC concentrations. Besides, PEI1200-C6 showed 4-16-fold better antibacterial effect than PEI1200, and fluorescent microscope imaging demonstrated that both of them could efficiently eradicate biofilms formed by four bacterial strains in vitro. As the accessible broad-spectrum antibacterial agents, PEI1200 and PEI1200-C6 are significant candidates to treat bacterial infections or eradicate biofilms on indwelling medical devices.

The paradigm of using phenylboronic acid-decorated polymeric nanomaterials for advanced bio-application has been well established over the past decade. Phenylboronic acid and its derivatives are known to form reversible complexes with polyols, including sugar, diol and diphenol. This unique chemistry of phenylboronic acid has given many chances to be exploited for diagnostic and therapeutic applications. This review highlights the recent advances in fabrication of phenylboronic acid-decorated polymeric nanomaterials, especially focus on the interactions with glucose and sialic acid. Applications of these phenylboronic acid-decorated nanomaterials in drug delivery systems and biosensors are discussed.

Nanoparticles that respond to specific endogenous or exogenous stimuli in tumor tissues are actively being developed to address multidrug resistance owing to multiple advantages, including a prolonged circulation time, enhanced permeability and retention effect, and superior cellular uptake. Although some exciting results have been obtained, existing nanoparticles have limited routes to overcome the drug resistance of tumor cells; this limitation results in a failure to ablate resistant tumors via intravenous administration. To resolve this dilemma, we developed a smart theranostic nanoplatform with programmable particle size, activatable target ligands and in vivo multimodal imaging. This nanoplatform, which includes stealth zwitterionic coating, was shown to be quickly trapped in tumor tissue from the blood circulation within 5 min. Subsequently, the targeting moieties were activated in response to the acidic tumor microenvironment by triggering the zwitterionic shell detachment, driving the peeled nanoparticles to penetrate into tumor cells. These smart nanoparticles completely inhibited drug-resistant tumor growth and did not cause any damage to normal organ tissues in live animals. The designed nanoplatforms simultaneously acted as a nanoprobe for fluorescence imaging. Moreover, we also used noninvasive pharmacokinetic diffuse fluorescence tomography (DFT) to dynamically monitor and in situ real-time trace the nanoplatforms' behavior throughout the entire tumor in live animals. The nanoplatforms enabled rapid drug accumulation and deep penetration throughout the entire tumor. The rate of drug accumulation after the administration of nanoplatforms was five-fold higher compared with that after the administration of the free drug, which resulted in increased drug delivery efficiency and improved antitumor efficacy. Collectively, this hierarchical vehicle design provides promising insights for the development of theragnosis for multidrug resistant tumors.