Selective Entropy Gain-Driven Adsorption of Nanospheres onto Spherical Bacteria Endows Photodynamic Treatment with Narrow-Spectrum Activity

Indoor/Outdoor airborne microbiome characteristics in residential areas across four seasons and its indoor purification

Bioaerosols are more likely to accumulate in the residential environment, and long-term inhalation may lead to a variety of diseases and allergies. Here, we studied the distribution, influencing factors and diffusion characteristics of indoor and outdoor microbiota pollution in six residential buildings in Guangzhou, southern China over a period of one year. The results showed that the particle sizes of bioaerosol were mainly in the range of inhalable particle size (<4.7 μm) with a small difference among four seasons (74.61 % ± 2.17 %). The microbial communities showed obvious seasonal differences with high abundance in summer, but no obvious geographical differences. Among them, the bacteria were more abundant than the fungi. The dominant microbes in indoor and outdoor environments were similar, with Anoxybacillu, Brevibacillus and Acinetobacter as the dominant bacteria, and Cladosporium, Penicillium and Alternaria as the dominant fungi. The airborne microbiomes were more sensitive to temperature and particulate matter (PM2.5, PM10) concentrations. Based on the Sloan neutral model, bacteria were more prone to random diffusion than fungi, and the airborne microbiome can be randomly distributed in indoor and outdoor environments and between the two environments in each season. Bioaerosol in indoor was mainly from outdoor. The health risk evaluation showed that the indoor inhalation risks were higher than those outdoor. The air purifier had a better removal efficiency on 1.1-4.7 μm microorganisms, and the removal efficiency on Gram-negative bacteria was better than that on Gram-positive bacteria. This study is of great significance for the risk assessment and control of residential indoor bioaerosol exposure.

High biocompatible FITC-conjugated silica nanoparticles for cell labeling in both in vitro and in vivo models

Fluorescence nanosilica-based cell tracker has been explored and applied in cell biological research. However, the aggregation of these nanoparticles at physiological pH is still the main limitation. In this research, we introduced a novel fluorescence nano-based cell tracker suitable for application in live cells. The silica-coated fluorescein isothiocyanate isomer (FITC-SiO2) nanoparticles (NPs) were modified with carboxymethylsilanetriol disodium salt (FITC-SiO2-COOH), integrating the dianion form of FITC molecules. This nanosystem exhibited superior dispersion in aqueous solutions and effectively mitigated dye leakage. These labeled NPs displayed notable biocompatibility and minimal cytotoxicity in both in vitro and in vivo conditions. Significantly, the NPs did not have negative implications on cell migration or angiogenesis. They successfully penetrated primary fibroblasts, human umbilical vein endothelial cells and HeLa cells in both 2D and 3D cultures, with the fluorescence signal enduring for over 72 h. Furthermore, the NP signals were consistently observed in the developing gastrointestinal tract of live medaka fish larvae for extended periods during phases of subdued digestive activity, without manifesting any apparent acute toxicity. These results underscore the promising utility of FITC-SiO2-COOH NPs as advanced live cell trackers in biological research.

Specific nanoantibiotics for selective removal of antibiotic-resistant bacteria: New insights in bacterial imprinting based on interfacial biomimetic mineralization

Antibiotic resistance has been a worsening global concern and selective elimination of antibiotic-resistant bacteria (ARB) while retaining the co-existed beneficial bacteria has been essential in environmental protection, which having attracted considerable interest. In this work, by integrating the whole cell imprinting and epitope imprinting strategy, magnetic bacterial imprinted polymers (BIPs) towards ARB were synthesized with interfacial biomimetic mineralization followed by a screening process. The binding data showed that the BIPs owned highly specific affinity towards the target bacteria. Taking advantage of this specific binding ability of BIPs, a two-step selective antimicrobial approach was developed. Remarkably, the BIP nanoantibiotics (nAbts) could efficiently destroy ARB without harming the beneficial bacteria. In comparison with the non-bacterial imprinted polymers, the biocompatible BIP nAbts showed a 12.5-fold increase in the survival percentage for the beneficial bacteria in wastewater. To the best of our knowledge, this is the first time that bacterial imprinting via interfacial biomimetic mineralization was developed, and also the first report of killing ARB without harming the beneficial bacteria in wastewater. We believe that this strategy provides a new insight into the design of novel affinity materials for the selective elimination of ARB in biological treatment for environmental protection.

Boronic Acid-Based Dendrimers with Various Surface Properties for Bacterial Recognition with Adjustable Selectivity

The need for a selective bacterial recognition method is evident to overcome the global problem of antibiotic resistance. Even though researchers have focused on boronic acid-based nanoprobes that immediately form boronate esters with saccharides at room temperature, the mechanism has not been well studied. We have developed boronic acid-modified poly(amidoamine) (PAMAM) dendrimers with various surface properties to investigate the mechanism of bacterial recognition. The boronic acid-based nanoprobes showed selectivity toward strains, species, or a certain group of bacteria by controlling their surface properties. Our nanoprobes showed selectivity toward Gram-positive bacteria or Escherichia coli K12W3110 without having to modify the boronic acid recognition sites. The results were obtained in 20 min and visible to the naked eye. Selectivity toward Gram-positive bacteria was realized through electrostatic interaction between the bacterial surface and the positively charged nanoprobes. In this case, the recognition target was lipoteichoic acid on the bacterial surface. On the other hand, pseudo-zwitterionic nanoprobes showed selectivity for E. coli K12W3110, indicating that phenylboronic acid did not recognize the outermost O-antigen on the lipopolysaccharide layer. Boronic acid-based nanoprobes with optimized surface properties are expected to be a powerful clinical tool to recognize multidrug-resistant strains or highly pathogenic bacteria.

A Biofilm Microenvironment-Activated Single-Atom Iron Nanozyme with NIR-Controllable Nanocatalytic Activities for Synergetic Bacteria-Infected Wound Therapy

Biofilm microenvironment (BME)-activated antimicrobial agents display great potential for improved biofilm-related infection therapy because of their superior specificities and sensitivities, effective eliminations, and minimal side effects. Herein, BME-activated Fe-doped polydiaminopyridine nanofusiform-mediated single-atom nanozyme (FePN SAzyme) is presented for photothermal/chemodynamic synergetic bacteria-infected wound therapy. The photothermal therapy (PTT) function of SAzyme can be specifically initiated by the high level of H₂ O₂ and further accelerated through mild acid within the inflammatory environment through "two-step rocket launching-like" process. Additionally, the enhanced chemodynamic therapy (CDT) for the FePN SAzyme can also be endowed by producing hydroxyl radicals through reacting with H₂ O₂ and consuming glutathione (GSH) of the BME, thereby contributing to more efficient synergistic therapeutic effect. Meanwhile, FePN SAzyme could catalyze biofilm-overexpressed H₂ O₂ decomposing into O₂ and overcome the hypoxia of biofilm, which significantly enhances the susceptibility of biofilm and increases the synergistic efficacy. Most importantly, the synergistic therapy of bacterial-induced infection diseases can be switched on by the internal and external stimuli simultaneously, resulting in minimal nonspecific damage to healthy tissue. These remarkable characteristics of FePN SAzyme not only develop an innovative strategy for the BME-activated combination therapy but also open a new avenue to explore other nanozyme-involved nanoplatforms for bacterial biofilm infections.

Covalent and Noncovalent Conjugation of Degradable Polymer Nanoparticles to T Lymphocytes

Cells are attractive as carriers that can help to enhance control over the biodistribution of polymer nanomedicines. One strategy to use cells as carriers is based on the cell surface immobilization of the nanoparticle cargo. While a range of strategies can be used to immobilize nanoparticles on cell surfaces, only limited effort has been made to investigate the effect of these surface modification chemistries on cell viability and functional properties. This study has explored seven different approaches for the immobilization of poly(lactic acid) (PLA) nanoparticles on the surface of two different T lymphocyte cell lines. The cell lines used were human Jurkat T cells and CD4⁺ T_EM cells. The latter cells possess blood-brain barrier (BBB) migratory properties and are attractive for the development of cell-based delivery systems to the central nervous system (CNS). PLA nanoparticles were immobilized either via covalent active ester-amine, azide-alkyne cycloaddition, and thiol-maleimide coupling, or via noncovalent approaches that use lectin-carbohydrate, electrostatic, or biotin-NeutrAvidin interactions. The cell surface immobilization of the nanoparticles was monitored with flow cytometry and confocal microscopy. By tuning the initial nanoparticle/cell ratio, T cells can be decorated with up to ∼185 nanoparticles/cell as determined by confocal microscopy. The functional properties of the nanoparticle-decorated cells were assessed by evaluating their binding to ICAM-1, a key protein involved in the adhesion of CD4⁺ T_EM cells to the BBB endothelium, as well as in a two-chamber model in vitro BBB migration assay. It was found that the migratory behavior of CD4⁺ T_EM cells carrying carboxylic acid-, biotin-, or Wheat germ agglutinin (WGA)-functionalized nanoparticles was not affected by the presence of the nanoparticle payload. In contrast, however, for cells decorated with maleimide-functionalized nanoparticles, a reduction in the number of migratory cells compared to the nonmodified control cells was observed. Investigating and understanding the impact of nanoparticle-cell surface conjugation chemistries on the viability and properties of cells is important to further improve the design of cell-based nanoparticle delivery systems. The results of this study present a first step in this direction and provide first guidelines for the surface modification of T cells, in particular in view of their possible use for drug delivery to the CNS.

Theranostic platforms for specific discrimination and selective killing of bacteria

Bacterial infections are serious threats to public health due to lack of advanced techniques to rapidly and accurately diagnose these infections in clinics. Although bacterial infections can be treated with broad-spectrum antibiotics based on empirical judgment, the emergence of antimicrobial resistance has attracted global attention due to long-term misuse and abuse of antibiotics by humans in recent decades. Therefore, it is imperative to selectively discriminate and precisely eliminate pathogenic bacteria. Herein, in addition to the conventional methods for bacterial identification, we comprehensively reviewed the recently developed theranostic platforms for specific discrimination and selective killing of bacteria according to their different interactions with the target bacteria, such as electrostatic and hydrophobic interactions, molecular recognition, microenvironment response, metabolic labeling, bacteriophage targeting, and others. These theranostic agents not only benefit from improved therapeutic efficiency but also present limited susceptibility to induce bacterial resistance. The strategies summarized in this review will open up new avenues in developing effective antimicrobial materials to accurately diagnose and treat bacterial infections in the post-antibiotic era. STATEMENT OF SIGNIFICANCE: Bacterial infections are difficult to be rapidly and accurately diagnosed, and are generally treated with broad-spectrum antibiotics, which leads to the development of drug resistance. By integrating imaging modalities and therapeutic methods in a single treatment, various theranostic agents have been developed to address the abovementioned issues. Therefore, the emerging theranostic platforms for selective identification and elimination of bacteria based on the distinct interactions of the theranostic agents with the target bacteria are summarized in this review. We believe that the information provided in this review will guide researchers in designing advanced antibacterial theranostics for practical applications in the post-antibiotic era.

Fluorescence-Based and Fluorescent Label-Free Characterization of Polymer Nanoparticle Decorated T Cells

Cells are attractive carriers for the transport and delivery of nanoparticulate cargo. The use of cell-based carriers allows one to enhance control over the biodistribution of drug-loaded polymers and polymer nanoparticles. One key element in the development of cell-based delivery systems is the loading of the cell-based carrier with the nanoparticle cargo, which can be achieved either by internalization of the payload or by immobilization on the cell surface. The surface modification of cells with nanoparticles or the internalization of nanoparticles by cells is usually monitored with fluorescence-based techniques, such as flow cytometry and confocal microscopy. In spite of the widespread use of these techniques, the use of fluorescent labels also poses some risks and has several drawbacks. Fluorescent dyes may bleach, or leach from, the nanoparticles or alter the physicochemical properties of nanoparticles and their interactions with and uptake by cells. Using poly(d,l-lactic acid) nanoparticles that are loaded with Coumarin 6, BODIPY 493/503, or DiO dyes as a model system, this paper demonstrates that the use of physically entrapped fluorescent labels can lead to false negative or erroneous results. The use of nanoparticles that contain covalently tethered fluorescent dyes instead was found to provide a robust approach to monitor cell surface conjugation reactions and to quantitatively analyze nanoparticle-decorated cells. Finally, it is shown that optical diffraction tomography is an attractive, alternative technique for the characterization of nanoparticle-decorated cells, which obviates the need for fluorescent labels.