Design and Application of Conjugated Polymer Nanomaterials for Detection and Inactivation of Pathogenic Microbes

Literature Review on Conjugated Polymers as Light-Sensitive Materials for Photovoltaic and Light-Emitting Devices in Photonic Biomaterial Applications

Due to their extended p-orbital delocalization, conjugated polymers absorb light in the range of visible-NIR frequencies. We attempt to exploit this property to create materials that compete with inorganic semiconductors in photovoltaic and light-emitting materials. Beyond competing for applications in photonic devices, organic conjugated compounds, polymers, and small molecules have also been extended to biomedical applications like phototherapy and biodetection. Recent research on conjugated polymers has focused on bioapplications based on the absorbed light energy conversions in electric impulses, chemical energy, heat, and light emission. In this review, we describe the working principles of those photonic devices that have been applied and researched in the field of biomaterials.

Chemo-photothermal therapy of chitosan/gold nanorod clusters for antibacterial treatment against the infection of planktonic and biofilm MRSA

Bacterial infections trigger inflammation and impede the closure of skin wounds. The misuse of antibiotics exacerbates skin infections by generating multidrug-resistant bacteria. In this study, we developed chemo-photothermal therapy (chemo-PTT) based on near-infrared (NIR)-irradiated chitosan/gold nanorod (GNR) clusters as anti-methicillin-resistant Staphylococcus aureus (MRSA) agents. The nanocomposites exhibited an average size of 223 nm with a surface charge of 36 mV. These plasmonic nanocomposites demonstrated on-demand and rapid hyperthermal action under NIR. The combined effect of positive charge and PTT by NIR-irradiated nanocomposites resulted in a remarkable inhibition rate of 96 % against planktonic MRSA, indicating a synergistic activity compared to chitosan nanoparticles or GNR alone. The nanocomposites easily penetrated the biofilm matrix. The combination of chemical and photothermal treatments by NIR-stimulated clusters significantly damaged the biofilm structure, eradicating MRSA inside the biomass. NIR-irradiated chitosan/GNR clusters increased the skin temperature of mice by 13 °C. The plasmonic nanocomposites induced negligible skin irritation in vivo. In summary, this novel nanosystem demonstrated potent antibacterial effects against planktonic and biofilm MRSA, showcasing the possible efficacy in treating skin infections.

Conjugated polymer nanoparticles as sonosensitizers in sono-inactivation of a broad spectrum of pathogens

Sonodynamic inactivation (SDI) of pathogens has an important advantage when compared to optical excitation-based protocols due to the deeper penetration of ultrasound (US) excitation in biological media or animal tissue. Sonosensitizers (SS) are compounds or systems that upon US stimulation in the therapeutic window (frequency = 0.8-3 MHz and intensity < 3 W/cm2) can induce damage to vital components of pathogenic microorganisms. Herein, we report the synthesis and application of conjugated polymer nanoparticles (CPNs) as an efficient SS in SDI of methicillin-resistant Staphylococcus aureus (MRSA), Klebsiella pneumoniae and Candida tropicalis. A frequent problem in the design and testing of new SS for SDI is the lack of proper sonoreactor characterization which leads to reproducibility concerns. To address this issue, we performed dosimetry experiments in our setup. This enables the validation of our results by other researchers and facilitates meaningful comparisons with different SDI systems in future studies. On a different note, it is generally accepted that the mechanisms of action underlying SS-mediated SDI involve the production of reactive oxygen species (ROS). In an attempt to establish the nature of the cytotoxic species involved in our CPNs-based SDI protocol, we demonstrated that singlet oxygen (1O2) does not play a major role in the observed sonoinduced killing effect. SDI experiments in planktonic cultures of optimally growing pathogens using CPNs result in a germicide effect on the studied pathogenic microorganisms. The implementation of SDI protocols using CPNs was further tested in mature biofilms of a MRSA resulting in ∼40 % reduction of biomass and ∼70 % reduction of cellular viability. Overall, these results highlight the unique and unexplored capacity of CPNs to act as sonosensitizers opening new possibilities in the design and application of novel inactivation protocols against morbific microbes.

Phosphonium-Substituted Conjugated Polyelectrolytes Display Efficient Visible-Light-Induced Antibacterial Activity

We report the light-activated antibacterial activity of a new class of phosphonium (R-PMe3+)-substituted conjugated polyelectrolytes (CPEs). These polyelectrolytes feature a poly(phenylene ethynylene) (PPE) conjugated backbone substituted with side groups with the structure -O-(CH2)nPMe3+, where n = 3 or 6. The length of the side groups has an effect on the hydrophobic character of the CPEs and their propensity to interact with bacterial membranes. In a separate study, these phosphonium-substituted PPE CPEs were demonstrated to photosensitize singlet oxygen (1O2) and reactive oxygen species, a key factor for the photoinduced inactivation of bacteria. In this study, in vitro antibacterial assays against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus were performed by employing the series of polyelectrolytes under both dark and illumination conditions. In general, the phosphonium-substituted CPEs displayed profound light-activated biocidal activity, with >99% colony forming unit (CFU) reduction after 15 min of light exposure (16 mW cm-2) at a ≤20 μM CPE concentration. Strong biocidal activity was also observed in the dark for a CPE concentration of 20 μM against S. aureus; however, higher concentrations (200 μM) were needed to enable dark inactivation of E. coli. The dark activity is ascribed to bacterial membrane disruption by the CPEs, supported by a correlation of dark biocidal activity with the chain length of the side groups. The light-activated biocidal activity is associated with the ability of the CPEs to sensitize ROS, which is cytotoxic to the microorganisms. Serial dilution bacterial plating experiments revealed that the series of CPEs was able to induce a >5-log kill versus E. coli with 15 min of exposure to a blue LED source (16 mW cm-2).

Positively Charged Semiconductor Conjugated Polymer Nanomaterials with Photothermal Activity for Antibacterial and Antibiofilm Activities In Vitro and In Vivo

Biofilm infections are associated with most human bacterial infections and are prone to bacterial multidrug resistance. There is an urgent need to develop an alternative approach to antibacterial and antibiofilm agents. Herein, two positively charged semiconductor conjugated polymer nanoparticles (SPPD and SPND) were prepared for additive antibacterial and antibiofilm activities with the aid of positive charge and photothermal therapy (PTT). The positive charge of SPPD and SPND was helpful in adhering to the surface of bacteria. With an 808 nm laser irradiation, the photothermal activity of SPPD and SPND could be effectively transferred to bacteria and biofilms. Under the additive effect of positive charge and PTT, the inhibition rate of Staphylococcus aureus (S. aureus) treated with SPPD and SPND (40 μg/mL) could reach more than 99.2%, and the antibacterial activities of SPPD and SPND against S. aureus biofilms were 93.5 and 95.8%. SPPD presented better biocompatibility than SPND and exhibited good antibiofilm properties in biofilm-infected mice. Overall, this additive treatment strategy of positive charge and PTT provided an optional approach to combat biofilms.

Novel Application of NIR-I-Absorbing Quinoidal Conjugated Polymer as a Photothermal Therapeutic Agent

Conjugated polymer nanoparticles (CP NPs) that could absorb the first near-infrared (NIR-I) window have emerged as highly desirable therapeutic nanomaterials. Here, a quinoidal-conjugated polymer (QCP), termed PQ, was developed as a novel class of therapeutic agents for photothermal therapy (PTT). Owing to its intrinsic quinoid structure, PQ exhibits molecular planarity and π-electron overlap along the conjugated backbone, endowing it with a narrow band gap, NIR-I absorption, and diradical features. The obtained PQ was coated with a poly(ethylene glycol) (PEG) moiety, affording nanosized and water-dispersed PQ nanoparticles (PQ NPs), which consequently show a high photothermal conversion efficiency (PCE) of 63.2%, good photostability, and apparent therapeutic efficacy for both in vitro and in vivo PTTs under an 808 nm laser irradiation. This study demonstrates that QCPs are promising active agents for noninvasive anticancer therapy using NIR-I light.

Bright NIR-Emitting Styryl Pyridinium Dyes with Large Stokes' Shift for Sensing Applications

Two NIR-emitting donor-π-acceptor (D-π-A) type regioisomeric styryl pyridinium dyes (1a-1b) were synthesized and studied for their photophysical performance and environment sensitivity. The two regioisomers, 1a and 1b, exhibited interesting photophysical properties including, longer wavelength excitation (λex ≈ 530-560 nm), bright near-infrared emission (λem ≈ 690-720 nm), high-fluorescence quantum yields (ϕfl ≈ 0.24-0.72) large Stokes' shift (∆λ ≈ 150-240 nm) and high-environmental sensitivity. Probe's photophysical properties were studied in different environmental conditions such as polarity, viscosity, temperature, and concentration. Probes (1a-1b) exhibited noticeable changes in absorbance, emission and Stokes' shift while responding to the changes in physical environment. Probe 1b exhibited a significant bathochromic shift in optical spectra (∆λ ≈ 20-40 nm) compared to its isomer 1a, due to the regio-effect. Probes (1a-1b) exhibited an excellent ability to visualize bacteria (Bacillus megaterium, Escherichia coli), and yeast (Saccharomyces cerevisiae) via fluorescence microscopy.

Theranostic FRET Gate to Visualize and Quantify Bacterial Membrane Breaching

Designing new antimicrobial-cum-probes to study real-time bacterial membrane breaching and concurrently developing inquisitorial image-based analytical tools is essential for the treatment of infectious diseases. An array of aggregation-induced emission (AIE) polymers (donor) consisting of neutral, anionic, and cationic charges were designed and employed as antimicrobial theranostic gatekeepers for the permeabilization of the peptidoglycan layer-adherable crystal violet (CV, acceptor). An AIE-active tetraphenylethylene (TPE)-tagged polycaprolactone biodegradable platform was chosen, and their self-assembled tiny amphiphilic nanoparticles were employed as a gatekeeper in the construction of bacterial membrane-reinforced fluorescent resonance energy transfer (FRET) probes. Electrostatic adhering of the cationic AIE polymer and subsequent gate opening aided fluorescent FRET probe activation on the membrane of Gram-negative bacteria, Escherichia coli. The selective photoexcitation energy transfer process in confocal microscopy experiments facilitated the building of a visualization-based FRET assay for the quantification of bactericidal activity. Nonantimicrobial AIE polymers (neutral and anionic) did not breach the bacterial membrane, resulting in no FRET signal. Detailed photophysical studies were done to establish the FRET probe mechanism, and a proof of concept was established.

Photodynamic Antimicrobial Therapy Based on Conjugated Polymers

Pathogenic microorganisms have been a serious threat to human life and have become a public health problem of global concern. However, in the actual treatment there is a lack of efficient antimicrobial strategies which do not easily develop drug resistance; this can lead to inaccurate drug treatment that worsens the infection and even threatens life. With the emergence of a variety of drug-resistant bacteria and fungi, photodynamic therapy has gradually become one of the most promising treatment methods for drug-resistant bacteria infection; this is because it is controllable, non-invasive, and not prone to cause the development of drug resistance. Organic conjugated polymers that possess high fluorescence intensity, a large molar extinction coefficient, excellent light stability, an adjustable energy band, easy modification, good biocompatibility, and the ability to photosensitize oxygen to produce reactive oxygen species have been widely used in the fields of solar cells, highly sensitive detection systems, biological imaging, and anti-cancer and anti-microbial treatment. Photodynamic therapy is non-invasive and has high temporal and spatial resolution and is a highly effective antimicrobial treatment that does not easily induce drug resistance; it has also stimulated the scientific research enthusiasm of researchers and has become a research hotspot in the antimicrobial field. In this review, the photodynamic antibacterial applications of conjugated polymers with different structure types are summarized, and their development directions are considered.

Luminescence-enhanced conjugated polymer dots through thermal treatment for cell imaging

Conjugated polymer dots (Pdots) are often used as excellent fluorescent probes in the biomedical field. In the process of preparing Pdots, the rapid change of the solvent polarity will result in a messy and defective stacking of the polymer chains in the particle, and these stacking defects of the polymer chains may weaken its luminescence properties. Here, we try to optimize the stacking of the conjugated polymer chains by the thermal annealing treatment. After the low temperature thermal treatment, the fluorescence intensity of Pdots can be enhanced by about 11%-29%, and Pdots maintain their original stability and biosafety. We used transmission electron microscopy (TEM) and single particle fluorescence imaging to reveal the possible mechanism of the chain stacking optimization process, that is, the thermal annealing process of Pdots is the competition between internal chain rearrangement in the particle and particle aggregation. The luminescence-enhanced Pdots exhibit good cellular imaging performance. These results prove that it is feasible to extend the thermal annealing treatment from planar polymer devices to polymer nanoparticles. It provides the possibility to realize stable and complex biological imaging applications using Pdots with a simple molecular structure, and a mature improvement scheme for the mass preparation of Pdots.

Fluorescent sensor array based on aggregation-induced emission luminogens for pathogen discrimination

A high-throughput tetraphenylethylene (TPE)-based fluorescent sensor array was constructed for the identification and detection of microorganisms, which utilizes three TPE derivatives with different numbers of cationic side chains to detect and discriminate various microorganisms at concentrations down to 1 × 10³ CFU mL^-1.

Flexible bioelectronic device fabricated by conductive polymer-based living material

Living materials are worked as an inside collaborative system that could naturally respond to changing environmental conditions. The regulation of bioelectronic processes in living materials could be effective for collecting biological signals and detecting biomarkers. Here, we constructed a living material with conjugated polymers poly[3-(3'-N,N,N-triethylamino-1'-propyloxy)-4-methyl-2,5-thiophene chloride] (PMNT) and Shewanella oneidensis MR-1 biofilm. In addition, the living material was integrated as a flexible bioelectronic device for lactate detection in physiological fluids (sweat, urine, and plasma). Owing to the electroconductivity of conjugated polymers, PMNT could optimize the bioelectronic process in the living material. The collected electrical signal could be wirelessly transferred to a portable smartphone for reading and analyzing. Because lactate is also a biomarker for cancer treatment, the flexible bioelectronic device was further used to detect and count the cancer cells. The proof of the bioelectronic device using conductive polymer-based living material exhibits promising applications in the next-generation personal health monitoring systems.

Conjugated Molecule-Assisted Supramolecular Hydrogel with Enhanced Antibacterial and Antibiofouling Properties

The hydrogel using natural and synthetic polymers to create a cross-linking network has drawn attention in diverse bioapplications. However, inhibition of bacterial infection is still a challenge for hydrogel's wide application. In this work, we reported a supramolecular hydrogel with a good antibacterial property built from conjugated molecules. The water-soluble molecular 4,7-bis[9,9-di(2-carboxy-ethyl)-fluoren-2-yl]-2,1,3-benzothiadiazole (OFBTCOOH) physically linked with monomers via hydrophobic interaction. The free-radical polymerized poly(N-acryloyl glycinamide) was hydrogen-bond cross-linked by dual amides in the side chains to form a hydrogel. An adjustable micro-network was obtained by increasing OFBTCOOH with evidence of enhanced intermolecular interaction. The successfully integrated OFBTCOOH could be excited upon light irradiation. The energy of triplet-state excitons of OFBTCOOH transferred to the ground-state oxygen to produce singlet oxygen, which endowed the hydrogel with the antibacterial property. Meanwhile, the superhydrophilic surface of the hydrogel can bind water molecules to form a stable hydration layer, which acted as barriers to resist protein and bacterial adsorption and achieve the anti-biofouling goal. The ease in introducing conjugated polyelectrolytes may provide a formulation to functionalize hydrogels via various physical interactions.

Functionalization of Water-Soluble Conjugated Polymers for Bioapplications

Water-soluble conjugated polymers (WS-CPs) have found widespread use in bioapplications ranging from in vitro optical sensing to in vivo phototherapy. Modification of WS-CPs with specific molecular functional units is necessary to enable them to interact with biological targets. These targets include proteins, nucleic acids, antibodies, cells, and intracellular components. WS-CPs have been modified with covalently linked sugars, peptides, nucleic acids, biotin, proteins, and other biorecognition elements. The objective of this article is to comprehensively review the various synthetic chemistries that have been used to covalently link biofunctional groups onto WS-CP platforms. These chemistries include amidation, nucleophilic substitution, Click reactions, and conjugate addition. Different types of WS-CP backbones have been used as platforms including poly(fluorene), poly(phenylene ethynylene), polythiophene, poly(phenylenevinylene), and others. Example applications of biofunctionalized WS-CPs are also reviewed. These include examples of protein sensing, flow cytometry labeling, and cancer therapy. The major challenges and future development of functionalized conjugated polymers are also discussed.

Carbon Dots in the Detection of Pathogenic Bacteria and Viruses

Bacterial and viruses pathogens are a significant hazard to human safety and health. In the imaging and detection of pathogenic microorganisms, the application of fluorescent nanoparticles is very useful. Carbon dots and quantum dots are preferred in this regard as labels, amplifiers, and/or electrode modifiers because of their outstanding features. However, precise diagnostics to identify numerous harmful bacteria simultaneously still face considerable hurdles, yet it is an inevitable issue. With the growing development of biosensors, nanoproduct-based bio-sensing has recently become one of the most promising methods for accurately identifying and quantifying various pathogens at low cost, high sensitivity, and selectivity, with time savings. The most recent applications of carbon dots in optical and electrochemical-based sensors are discussed in this review, along with some examples of pathogen sensors.HighlightsSimultaneous and early detection of pathogens is a critical issue in the management of readily spread to prevent epidemics.Carbon dots-based biosensors are more preferred in detection of pathogens due to high selectivity and sensitivity, as well as quick and cheap point-of-care platform.Summary of recent advances in the design of optical and electrochemical biosensors for the detection of pathogens.

Nanomaterials: The New Antimicrobial Magic Bullet

Bacterial infections are a significant cause of mortality and morbidity worldwide, despite decades of use of numerous existing antibiotics and constant efforts by researchers to discover new antibiotics. The emergence of infections associated with antibiotic-resistant bacterial strains, has amplified the pressure to develop additional bactericidal therapies or new unorthodox approaches that can deal with antimicrobial resistance. Nanomaterial-based strategies, particularly those that do not rely on conventional small-molecule antibiotics, offer promise in part due to their ability to dodge existing mechanisms used by drug-resistant bacteria. Therefore, the use of nanomaterial-based formulations has attracted attention in the field of antibiotic therapy. In this Review, we highlight novel and emerging nanomaterial-based formulations along with details about the mechanisms by which nanoparticles can target bacterial infections and antimicrobial resistance. A detailed discussion about types and the activities of nanoparticles is presented, along with how they can be used as either delivery systems or as inherent antimicrobials, or a combination of both. Lastly, we highlight some toxicological concerns for the use of nanoparticles in antibiotic therapies.

Solar-Driven Producing of Value-Added Chemicals with Organic Semiconductor-Bacteria Biohybrid System

Photosynthetic biohybrid systems exhibit promising performance in biosynthesis; however, these systems can only produce a single metabolite and cannot further transform carbon sources into highly valuable chemical production. Herein, a photosynthetic biohybrid system integrating biological and chemical cascade synthesis was developed for solar-driven conversion of glucose to value-added chemicals. A new ternary cooperative biohybrid system, namely bacterial factory, was constructed by self-assembling of enzyme-modified light-harvesting donor-acceptor conjugated polymer nanoparticles (D-A CPNs) and genetically engineered Escherichia coli (E. coli). The D-A CPNs coating on E. coli could effectively generate electrons under light irradiation, which were transferred into E. coli to promote the 37% increment of threonine production by increasing the ratio of nicotinamide adenine dinucleotide phosphate (NADPH). Subsequently, the metabolized threonine was catalyzed by threonine deaminase covalently linking with D-A CPNs to obtain 2-oxobutyrate, which is an important precursor of drugs and chemicals. The 2-oxobutyrate yield under light irradiation is increased by 58% in comparison to that in dark. This work provides a new organic semiconductor-microorganism photosynthetic biohybrid system for biological and chemical cascade synthesis of highly valuable chemicals by taking advantage of renewable carbon sources and solar energy.

Conjugated Polymer-Functionalized Stretchable Supramolecular Hydrogels to Monitor and Control Cellular Behavior

Natural extracellular matrix is formed by the assembly of small molecules and macromolecules into a hydrogel-like network that can mechanically support cells and involve in cellular processes. Here, we developed a fluorescent supramolecular hydrogel based on a conjugated oligomer OFBTCO₂Na, which facilitated noncovalent assembly through hydrophobic interactions and hydrogen bonds in a molecular scale. The generated dense three-dimensional network endows the supramolecular hydrogel with stretchability and stability. Furthermore, fluorescent OFBTCO₂Na in hydrogel acted as a donor, which can excite the acceptor dyes on cells encapsulated in hydrogel via the Förster resonance energy transfer (FRET) mechanism. Investigating the fluorescence signal responsiveness of hydrogel to dynamic mechanical stretching well reflected that enhanced stretching dictated the extent of connection between the cell and matrix, which enables effective FRET at a molecular level and allow spatiotemporally monitoring cell-matrix interactions at the three-dimensional network. Importantly, cells can sense stretch forces by their connection with a hydrogel matrix. The dynamic cell-matrix interaction can be conveniently employed to formulate cell morphology. Therefore, the fluorescent supramolecular hydrogel offers a suitable culture platform not only to investigate cell interactions on interfaces but also to regulate cell behavior at interfaces.

Bacteria-Mediated Intracellular Click Reaction for Drug Enrichment and Selective Apoptosis of Drug-Resistant Tumor Cells

Functionalized biocarriers that can perform bio-orthogonal reactions in tumor cells may provide solutions to overcome the efflux of the chemotherapeutic agent from drug-resistant tumor cells. Herein, we report the enrichment of therapeutic drugs in tumor cells through intracellular click reaction with functionalized bacteria. Specifically, an intracellular bioactive drug enrichment template (OPV@Escherichia coli) is constructed by combining positively charged oligo(phenylene-vinylene)-alkyne (OPV-C≡CH) with E. coli via electrostatic interaction. After the cell uptake of OPV@E. coli and Cu(II)-based complex, Cu(I) generated in situ can catalyze the bio-orthogonal click reaction to covalently anchor the azide-bearing molecules of cyanine 5 (Cy5-N₃) and paclitaxel (PTX-N₃) on OPV@E. coli. These molecules and their functions were retained and enriched inside the drug-resistant tumor cells A549T, which can label cells with fluorescent probes and selectively induce the apoptosis of drug-resistant tumor cells.

Aggregation-Induced Emission-Active Biomacromolecules: Progress, Challenges, and Opportunities

Biomacromolecules featuring aggregation-induced-emission (AIE) characteristics generally present new properties and performances that are silent in the molecular state, providing endless possibilities for the evolution of biomedical applications. Tremendous achievements based on the research of AIE-active biomacromolecules have been made in synthetic exploration, material development, and practical applications. In this Perspective, we give a brief account in the development of AIE-active biomacromolecules. Remarkable progresses have been made in the exploration of AIE-active biomacromolecule preparation, structure-property relationships, and the relevant biomedical applications. The existing challenges and promising opportunities, as well as the future directions in AIE-active biomacromolecule research, are also discussed. It is expected that this Perspective can act as a trigger for the innovation of AIE-active biomacromolecule research and aggregate science.

Controlling the Interaction between Fluorescent Gold Nanoclusters and Biointerfaces for Rapid Discrimination of Fungal Pathogens

Nondestructive detection and discrimination of fungal pathogens is essential for rapid and precise treatment, which further effectively prevents antifungal resistance from overused drugs. In this work, fluorescent gold nanoclusters served as the basis for discriminating Candida species. Varied on surface ligands, these gold nanoclusters demonstrated different optical properties as a result of the perturbation effects of ligands. The biointerface interaction between the surface ligands of gold nanoclusters and the cell walls of Candida species can be constructed, and their restriction on ligands perturbation effect produced enhanced fluorescence signals. Owing to the variation of the cell wall composition, cells of different Candida species demonstrated different degrees of association with the gold nanoclusters, leading to discriminable amounts of fluorescence enhancements. The reverse signal response from these gold nanoclusters gives rise to a synergistic and effective assay that allows identification of Candida species.

Cationic conjugated polymer-based FRET aptasensor for label-free and ultrasensitive ractopamine detection

A label-free fluorescence resonance energy transfer (FRET) platform based on cationic conjugated polymers and aptamers for ultrasensitive and specific ractopamine detection was constructed. This method exhibited a wide linear range from 0.05 to 500 μM and a low limit of detection of 47 nM, which make it an attractive assay platform for foodborne doping.

A label-free fluorescence resonance energy transfer (FRET) platform based on cationic conjugated polymers and aptamer has established for ultrasensitive and specific ractopamine (RAC) detection.

Simultaneous and visual detection of multiple dopes by an aptamer/AuNPs sensor

Through introducing multiple aptamers in a suitable ratio, we achieved the simultaneous and visual detection of three dopes in one sensor.

Design and Structural Regulation of AIE photosensitizers for imaging-guided photodynamic anti-tumor application

In recent years, photodynamic therapy (PDT) has become one of the important therapeutic methods for treating cancer. Aggregation-induced emission (AIE) photosensitizers (PSs) overcome the aggregation-caused quenching (ACQ) effects of conventional...

Lactoferrin-thymol complex for the disinfection of gram-positive Staphylococcus aureus and Gram-negative Escherichia coli

Seeking all-nature derived antibacterial agents with effective disinfection function, high human safety as well as environment-friendly characteristics are highly required in the food industry. Herein, we report the lactoferrin-thymol (LF-Thy) complex as an effective killing agent against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). The multi-spectroscopy results clearly demonstrate the combination of LF and Thy to form the LF-Thy complex, accompanied with LF conformation variations including the increase in the hydrophobicity of amino acid residues and changes in the types of secondary conformation distribution in LF. Molecular docking results show that LF exhibits three possible binding sites and five predicted stable binding modes for Thy with the help of hydrogen bonding and hydrophobic interactions. Moreover, LF-Thy demonstrated a significantly higher antibacterial ability compared to LF and displays effective disinfection function against E. coli and S. aureus. The minimum inhibitory concentration (MIC) of LF toward E. coli and S. aureus is >40 mg mL^-1 and 40 mg mL^-1, which decreases to 10 mg mL^-1 and 5 mg mL^-1 after combination with Thy, respectively. This work demonstrates the promising antibacterial activities of the LF-Thy complex and provides an alternative agent for combating bacterial infection in the food industry, which holds great potential for promoting the development of the all-natural healthcare food complex.

Near-Infrared-Light Remote-Controlled Activation of Cancer Immunotherapy Using Photothermal Conjugated Polymer Nanoparticles

Remote control of the therapeutic process is an ideal strategy for maximizing efficacy and avoiding side effects, especially for cancer immunotherapy. Herein, a conjugated polymer nanoparticles (CPNs)-mediated optogenetic system for in situ activation of immunotherapy under near-infrared laser irradiation is reported. This system is composed of photothermal CPNs and interferon-gamma (IFN-γ) plasmid driven by heat shock promoter HSP70. The photothermally responsive CPNs serve as a photo-heat nanotransducer to trigger the gene transcription of IFN-γ cytokine. The secreted IFN-γ from cancer cells can sufficiently elicit surrounding tumor-associated macrophages activation through IFN-γ-JAK-STAT1 transcription-factor signaling pathway and finally induce cancer cell killing by immunotherapy. Therefore, this synergetic optogenetic system provides a promising approach to remotely control the process of cancer immunotherapy.

Polymer nanoparticles regulate macrophage repolarization for antitumor treatment

We demonstrate an intrinsic antitumor effect of polymer nanoparticles (P-NPs), which could re-program tumor-associated macrophages to pro-inflammatory phenotype. The intrinsic effect of P-NPs on macrophage repolarization and its combination with other therapies provide new ideas for drug delivery, macrophage regulation and immunotherapy in cancer treatment.