The emergence and spread of bacterial resistance pose a serious threat to global public health security. Addressing this challenge requires the development of new antimicrobials and antimicrobial therapies. Narrow-spectrum antimicrobials/therapies specifically identify and eliminate the bacteria of interest, thereby reducing off-target interference with the host symbiotic flora and reducing evolutionary pressure on the bacteria' resistance. However, the development of narrow-spectrum antimicrobials/therapies has been extremely sluggish due to the inherent difficulty of distinguishing germs from probiotics and the lack of investment enthusiasm of pharmaceutical companies in narrow-spectrum antimicrobials. In response to this problem, the yang lihua research group of associate professor of the University of Science and Technology of China proposed to give existing broad-spectrum antibacterial substances/therapies the ability to identify target bacteria, thereby transforming them into a narrow-spectrum antibacterial substance/therapy.
Photodynamic therapy uses photodynamic sensitizers in response to in situ generated reactive oxygen species (ROS) by light to clear target cells. However, "success is also Xiao He, and failure is also Xiao He". On the one hand, because ROS can simultaneously destroy a variety of cellular substances that are essential for the normal function of cells, photodynamic therapy can eliminate resistant bacteria and at the same time delay the bacteria to acquire drug resistance. On the other hand, because ROS can indiscriminately remove cells from the place where it passes, photodynamic therapy is conventionally a broad-spectrum antimicrobial therapy.
Recently, Yang Lihua's research group found for the first time that when negatively charged nanospheres are mixed with bacteria, the nanospheres will selectively adsorb to the surface of cocci but not to the surface of bacilli, and this recognition mechanism based on bacterial morphology selection is driven by entropy increase and is generally suitable for a variety of nanospheres with different composition and surface chemistry. Based on this physical recognition mechanism and the extremely limited active radius of ROS (less than 200 nm) (above Figure 1), the researchers hypothesized that if the nanospheres had a photodynamic effect, they might be able to efficiently remove cocci under light without interfering with the bacteria (Figure 1 and bottom). This conjecture was confirmed by antimicrobial experiments using different photodynamic nanospheres and a variety of bacteria. The research was published in the journal The Journal of Physical under the title of Selective Entropy Gain-Driven Adsorption of Nanospheres onto Spherical Bacteria Endows Photodynamic Treatment with Narrow-Spectrum Activity On Chemistry Letters. This work not only reveals for the first time the critical role of bacterial morphology in similarly charged nanosphere/bacterial interactions, but is also expected to provide a new therapy for diseases such as allergic dermatitis caused by the over-multiplication of cocci in a microenvironment dominated by bacilli in a healthy symbiotic microenvironment.
The research was supported by a grant from the National Natural Science Foundation of China and the National Synchrotron Radiation Laboratory. Yang Lihua is the corresponding author of the paper, and Yang Binqian, a master student, is the first author of the paper.
Figure 1: (Top) Photodynamic nanospheres (PNS) generate reactive oxygen species (ROS) in situ under light. Negatively charged nanospheres are selectively adsorbed to the surface of the (medium) bulb bacteria without adsorbing to the surface of the (bottom) bacteria. If these nanospheres have a photodynamic effect, they can efficiently remove cocci under light without interfering with the bacteria.
Source: University of Science and Technology of China