Enhanced optical imaging properties of lipid nanocapsules as vehicles for fluorescent conjugated polymers

Photoinactivation of Multidrug-Resistant mcr-1-Positive E. coli Using PCPDTBT Conjugated Polymer Nanoparticles under White Light

The issue of antimicrobial resistance is an escalating concern within the scope of global health. It is predicted that the existence of antibiotic-resistant bacteria might result in an estimated annual death of up to 10 million by 2050, along with possible economic losses ranging from 100 to 210 trillion. This study reports the production of poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] nanoparticles (PCPDTBT-NPs) by nanoprecipitation as an alternative to tackle this problem. The size, shape, and optical features of these conjugated polymer NPs were analyzed. Their efficacy as photosensitizers against nonresistant (ATCC) and multidrug-resistant mcr-1-positive Escherichia coli was assessed under white light doses of 250 and 375 J·cm-2. PCPDTBT-NPs inactivated both E. coli strains exposed to white light at an intensity of 375 J·cm-2, while no antimicrobial effect was observed in the group not exposed to white light. Reactive oxygen species and singlet oxygen were detected using DCFH-DA and DPBF probes, allowing the investigation of the photoinactivation pathways. This work showcases PCPDTBT-NPs as photosensitizers to eliminate multidrug-resistant bacteria through photodynamic inactivation employing visible light.

π-Conjugated Polymer Nanoparticles from Design, Synthesis to Biomedical Applications: Sensing, Imaging, and Therapy

In the past decade, π-conjugated polymer nanoparticles (CPNs) have been considered as promising nanomaterials for biomedical applications, and are widely used as probe materials for bioimaging and drug delivery. Due to their distinctive photophysical and physicochemical characteristics, good compatibility, and ease of functionalization, CPNs are gaining popularity and being used in more and more cutting-edge biomedical sectors. Common synthetic techniques can be used to synthesize CPNs with adjustable particle size and dispersion. More importantly, the recent development of CPNs for sensing and imaging applications has rendered them as a promising device for use in healthcare. This review provides a synopsis of the preparation and functionalization of CPNs and summarizes the recent advancements of CPNs for biomedical applications. In particular, we discuss their major role in bioimaging, therapeutics, fluorescence, and electrochemical sensing. As a conclusion, we highlight the challenges and future perspectives of biomedical applications of CPNs.

The Role of Stabilizing Copolymer in Determining the Physicochemical Properties of Conjugated Polymer Nanoparticles and Their Nanomedical Applications

Conjugated polymer nanoparticles (CPNs) are a promising class of nanomaterials for biomedical applications, such as bioimaging, gene and drug delivery/release, photodynamic therapy (PDT), photothermal therapy (PTT), and environmental sensing. Over the past decade, many reports have been published detailing their synthesis and their various potential applications, including some very comprehensive reviews of these topics. In contrast, there is a distinct lack of overview of the role the stabilizing copolymer shells have on the properties of CPNs. This review attempts to correct this oversight by scrutinizing reports detailing the synthesis and application of CPNs stabilized with some commonly-used copolymers, namely F127 (Pluronic poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) diacrylate), PSMA (poly(styrene-co-maleic anhydride)), PLGA (poly(D, L-lactide-co-glycolide)) and PEG (polyethylene glycol) derivatives. The analysis of the reported physicochemical properties and biological applications of these CPNs provides insights into the advantages of each group of copolymers for specific applications and offers a set of guidance criteria for the selection of an appropriate copolymer when designing CPNs-based probes. Finally, the challenges and outlooks in the field are highlighted.

Investigating conjugated polymer nanoparticle formulations for lateral flow immunoassays

Lateral flow immunoassays (LFI) are valuable tools for point-of-care testing. However, their sensitivity is limited and can be further improved. Nanoparticles (NP) of conjugated polymers (CPNs), also known as Pdots, are reported to be highly sensitive fluorescent probes, but a direct comparison with conventional colloidal gold-based (Au-NP) LFI using the same antibody-antigen pair is missing to date. Furthermore, the influence of brightness and Stokes shift of CPs on the signal : background ratio (SBR) needs to be evaluated. In this study, we encapsulated two different CPs, poly-(9,9-di-n-octyl-fluorenyl-2,7-diyl) (PDOF) and poly-(2,5-di-hexyloxy-cyanoterephthalylidene) (CN-PPV) in silica shell-crosslinked Pluronic© micelles (Si-NP) and Pdots and investigated the NP brightness with respect to CP loading dose. The brightest formulation of each NP system was conjugated to rabbit IgG as a model antigen and the SBR was investigated in an ELISA-like microplate assay and LFI. Two reference particles, Au-NP and a polystyrene NP (PS-NP) loaded with a small-molecule fluorescent dye were conjugated to IgG and compared to the Si-NP and Pdots. The mass of Pdots required for detection in LFI was at least two orders of magnitude lower than that of Si-NP and the reference NP. The SBR of CN-PPV (moderate brightness, large Stokes shift) was two to three times higher than the SBR of PDOF (high brightness, small Stokes shift). To combine the favourable properties of both CPs, a polymer blend of PDOF and CN-PPV was encapsulated in Pdots, and resulted in further increase of SBR in the microplate assay and LFI. In summary, combining two CPs with different properties can lead to fluorescent signal-transducers for applications such as ELISA and LFIs, which can enhance the detection limit of the assay by 2-3 orders of magnitude.