Development of folate-conjugated polypyrrole nanoparticles incorporated with nitrogen-doped carbon quantum dots for targeted bioimaging and photothermal therapy.

PPy nanoparticles are widely employed as PTT agents, because of their exceptional near-infrared absorption properties. Nonetheless, the efficacy of PTT with PPy nanoparticles is hindered by a challenge, specifically, a lack of precise targeting. In this study, a PTT imaging agent was developed by combining NCQDs having bright green fluorescent properties with PPy nanoparticles along with the masking of folic acid to overcome the challenge of targeting. The synthesized PPy:NCQDs:FA nanocomposite, characterized by extraordinary photothermal property, was utilized for imaging of folate receptor positive (FA+) MCF-7 cancer cells through the emission of green fluorescence by NCQDs incorporated within the nanocomposite. Additionally, these nanoparticles demonstrated a good level of cell viability, exceeding 82 %, even at a concentration of 600 µg mL-1. Even the in vivo toxicity inspection of the nanocomposite exemplified no observed acute toxicity at experimental dosages of 1 and 3 mg per kg body weight. By subjecting MCF-7 cells, inoculated with 100 µg mL-1 of nanocomposite, to NIR laser irradiation for 5 min, a significant decline in cell viability was witnessed, establishing the photothermal therapeutic potency of the nanocomposite. The death of cancer cells induced by nanocomposite was verified through MTT assay, imaging of cells by NCQDs alone, with nanocomposite, and by live/dead cell Calcein AM/PI staining assay. Quantification of induced apoptosis post-laser treatment is conducted through staining with Annexin V-FITC/PI. These findings establish potential use of PPy:NCQDs:FA nanocomposite as versatile theranostic agents, capable of targeted bioimaging and treatment for cancer cells exhibiting folate receptors.

Biomimetic copper-doped polypyrrole nanoparticles induce glutamine metabolism inhibition to enhance breast cancer cuproptosis and immunotherapy.

Cuproptosis, a newly discovered mechanism of inducing tumor cell death, primarily relies on the intracellular accumulation of copper ions. The utilization of Cu-based nanomaterials to induce cuproptosis holds promising prospects in future biomedical applications. However, the presence of high levels of glutathione (GSH) within tumor cells hinders the efficacy of cuproptosis. In this study, we have developed a BPTES-loaded biomimetic Cu-doped polypyrrole nanoparticles (CuP) nanosystem (PCB) for enhanced cuproptosis and immune modulation. PCB comprises an internal BPTES and CuP core and an external platelet membrane (PM) that facilitates active targeting to tumor sites following intravenous administration. Subsequently, PCB effectively suppresses glutaminase (GLS1) activity, thereby reducing GSH content. Moreover, CuP catalyze intracellular H2O2, amplifying oxidative stress while simultaneously inducing dihydrolipoyl transacetylase (DLAT) oligomerization through released Cu2+, resulting in cuproptosis. PCB not only inhibits primary tumors but also exhibits inhibitory effects on abscopal tumors. This work represents the first instance where GLS inhibition has been employed to enhance cuproptosis and immunotherapy. It also provides valuable insights into further investigations on cuproptosis.

Biomimetic Copper-Doped Polypyrrole Nanoparticles for Enhanced Cancer Low-Temperature Photothermal Therapy.

Introduction: Photothermal therapy (PTT) has a significant potential for its application in precision tumour therapy. However, PTT-induced hyperthermia may damage healthy tissues and trigger the expression of heat shock proteins (HSPs), thereby compromising the long-term therapeutic efficacy of PTT. Methods: In this study, a biomimetic drug delivery system comprising CuP nanozymes as the inner core and platelet membrane (PM) as the outer shell was successfully developed for administering synergistic chemodynamic therapy and mild PTT. PM is encapsulated on CuP to form this biomimetic nanoparticle (PM-coated CuP nanoparticles, PC). PC possesses peroxidase (POD) activity, can facilitate the conversion of hydrogen peroxide into ·OH, thereby inhibiting the expression of HSPs. Results: Upon exposure to low-power laser irradiation (0.5 W/cm2, 1064 nm), PC can convert near-infrared II laser energy into heat energy, thereby enabling the administration of enhanced mild PTT. In vitro and in vivo experiments have demonstrated that this synergistic approach can induce over 90% tumour eradication with favourable biocompatibility. Discussion: PC exhibits high efficacy and biocompatibility, making it a promising candidate for future applications.

Arrhythmic Effects Evaluated on Caenorhabditis elegans: The Case of Polypyrrole Nanoparticles.

Experimental studies and clinical trials of nanoparticles for treating diseases are increasing continuously. However, the reach to the market does not correlate with these efforts due to the enormous cost, several years of development, and off-target effects like cardiotoxicity. Multicellular organisms such as the Caenorhabditis elegans (C. elegans) can bridge the gap between in vitro and vertebrate testing as they can provide extensive information on systemic toxicity and specific harmful effects through facile experimentation following 3R EU directives on animal use. Since the nematodes' pharynx shares similarities with the human heart, we assessed the general and pharyngeal effects of drugs and polypyrrole nanoparticles (Ppy NPs) using C. elegans. The evaluation of FDA-approved drugs, such as Propranolol and Racepinephrine reproduced the arrhythmic behavior reported in humans and supported the use of this small animal model. Consequently, Ppy NPs were evaluated due to their research interest in cardiac arrhythmia treatments. The NPs' biocompatibility was confirmed by assessing survival, growth and development, reproduction, and transgenerational toxicity in C. elegans. Interestingly, the NPs increased the pharyngeal pumping rate of C. elegans in two slow-pumping mutant strains, JD21 and DA464. Moreover, the NPs increased the pumping rate over time, which sustained up to a day post-excretion. By measuring pharyngeal calcium levels, we found that the impact of Ppy NPs on the pumping rate could be mediated through calcium signaling. Thus, evaluating arrhythmic effects in C. elegans offers a simple system to test drugs and nanoparticles, as elucidated through Ppy NPs.

Novel Photodynamic/Photothermal Treatment of Fungal Keratitis Using Rose Bengal-Loaded Polypyrrole-Gold Nanoparticles in Wistar Albino Rats.

Purpose: Fungal keratitis is a potential corneal contagious disease mainly caused by yeast such as Candida albicans and filamentous fungi such as Aspergillus niger. The response of fungal keratitis to standard antifungals is limited by the poor bioavailability, the limited ocular penetration of antifungal drugs, and the development of microbial resistance. Photodynamic therapy using rose bengal (RB) as a photosensitizer was found to be effective in fungal keratitis management; however, the hydrophilicity of RB limits its corneal penetration. Polypyrrole-coated gold nanoparticles (AuPpy NP) were introduced as a nano-delivery system of RB with high loading capacity. It was proved that (RB-AuPpy NP) exhibited a combined photodynamic/photothermal effect. This study aims to use the combined photodynamic/photothermal effect of RB-AuPpy NP as a novel protocol for treating Fungal Keratitis in albino Wistar rats. Methods: The rats were infected by C. albicans and A. niger. Each infected group of rats was subdivided into groups treated by RB followed by radiation (photodynamic only), AuPpy NP followed by radiation (photothermal only), and RB-AuPpy NP followed by radiation (combined photodynamic/photothermal). Histopathological examination and slit lamp imaging were done to investigate the results. Results: The results revealed that 3 weeks post-treatment, the corneas treated by RB-AuPpy NP (combined photodynamic/photothermal effect) exhibited the best improvement compared to other groups. Conclusion: This protocol can be considered a promising one for Fungal Keratitis management that overcomes microbial resistance problems.

Effect of Ultrasonication Parameters on the Structural, Morphological, and Electrical Properties of Polypyrrole Nanoparticles and Optimization by Response Surface Methodology.

Polypyrrole (PPy) nanoparticles are reliable conducting polymers with many industrial applications. Nevertheless, owing to disadvantages in structure and morphology, producing PPy with high electrical conductivity is challenging. In this study, a chemical oxidative polymerization-assisted ultra-sonication method was used to synthesize PPy with high conductivity. The influence of critical sonication parameters such as time and power on the structure, morphology, and electrical properties was examined using response surface methodology. Various analyses such as SEM, FTIR, DSC, and TGA were performed on the PPy. An R2 value of 0.8699 from the regression analysis suggested a fine correlation between the observed and predicted values of PPy conductivity. Using response surface plots and contour line diagrams, the optimum sonication time and sonication power were found to be 17 min and 24 W, respectively, generating a maximum conductivity of 2.334 S/cm. Meanwhile, the model predicted 2.249 S/cm conductivity, indicating successful alignment with the experimental data and incurring marginal error. SEM results demonstrated that the morphology of the particles was almost spherical, whereas the FTIR spectra indicated the presence of certain functional groups in the PPy. The obtained PPy with high conductivity can be a promising conducting material with various applications, such as in supercapacitors, sensors, and other smart electronic devices.

Oomicidal activity of polypyrrole nanoparticles against Pythium insidiosum.

This study evaluated in-vitro action of a new molecule, the polypyrrole nanoparticles (Ppy-NP), against Pythium insidiosum isolates using M38-A2/CLSI; the minimal inhibitory (MIC) and minimal oomicidal (MOC) concentrations were also determined. Additionally, changes in the hyphae wall of P. insidiosum CBS 575.85 treated with Ppy-NP were evaluated by scanning electron microscopy (SEM). The MIC100 and MOC for all isolates ranged from 8 to 32 µg mL-1, and the MIC90 and MIC50 were 16 µg mL-1. The SEM showed structural damage to the hyphae of P. insidisoum treated with Ppy-NP, as hyphae surfaces with less turgidity were found, thereby showing scaling and ruptures compared to the control (untreated hyphae). Our findings highlighted the anti-P. insidiosum properties of Ppy-NP proved to be a promising candidate for research using pythiosis experimental models.

Mangasese doped polypyrole nanoparticels for photothermal/chemodynamic therapy and immune activation.

Photothermal therapy (PTT) is a promising treatment that efficiently suppresses local cancer, but fails to induce a robust antitumor immune response against tumor metastasis and recurrence. In this study, a NIR responsive nano-immunostimulant (Mn/A-HP NI) is fabricated by entrapping manganese and azo-initiator (AIPH) into hyaluronic acid-based polypyrrole nanoparticle. The as-prepared Mn/A-HP NIs with a high photothermal conversion efficiencey of 20.17% dramatically induced the imunogenic cell death of tumor cells and triggered the release ATP and HMGB1. Meanwhile, the hyperthermia induced AIPH decomposition to produce alkyl radicals which further destroyed cancer cells. Furthermore, the Mn/A-HP NIs were capable of promoting the maturation and antigen cross-presentation ability of dendritic cells. Consequently, the multifunctional Mn/A-HP NIs provided a combined treatment via integrating PTT/chemo-dynamic therapy and immune activation for tumor therapy.

Spatiotemporal Temperature Distribution of NIR Irradiated Polypyrrole Nanoparticles and Effects of pH.

The spatiotemporal temperature distributions of NIR irradiated polypyrrole nanoparticles (PPN) were evaluated by varying PPN concentrations and the pH of suspensions. The PPN were synthesized by oxidative chemical polymerization, resulting in a hydrodynamic diameter of 98 ± 2 nm, which is maintained in the pH range of 4.2-10; while the zeta potential is significantly affected, decreasing from 20 ± 2 mV to -5 ± 1 mV at the same pH range. The temperature profiles of PPN suspensions were obtained using a NIR laser beam (1.5 W centered at 808 nm). These results were analyzed with a three-dimensional predictive unsteady-state heat transfer model that considers heat conduction, photothermal heating from laser irradiation, and heat generation due to the water absorption. The temperature profiles of PPN under laser irradiation are concentration-dependent, while the pH increase only induces a slight reduction in the temperature profiles. The model predicts a value of photothermal transduction efficiency (η) of 0.68 for the PPN. Furthermore, a linear dependency was found for the overall heat transfer coefficient (U) and η with the suspension temperature and pH, respectively. Finally, the model developed in this work could help identify the exposure time and concentration doses for different tissues and cells (pH-dependent) in photothermal applications.

Fabrication of methylene blue-loaded ovalbumin/polypyrrole nanoparticles for enhanced phototherapy-triggered antitumour immune activation.

BACKGROUND: Phototherapy-triggered immunogenic cell death (ICD) rarely elicits a robust antitumour immune response, partially due to low antigen exposure and inefficient antigen presentation. To address these issues, we developed novel methylene blue-loaded ovalbumin/polypyrrole nanoparticles (MB@OVA/PPY NPs) via oxidative polymerization and π-π stacking interactions. RESULTS: The as-prepared MB@OVA/PPY NPs with outstanding photothermal conversion efficiency (38%) and photodynamic properties were readily internalized into the cytoplasm and accumulated in the lysosomes and mitochondria. Upon 808 nm and 660 nm laser irradiation, the MB@OVA/PPY NPs not only ablated tumour cells by inducing local hyperthermia but also damaged residual tumour cells by generating a large amount of reactive oxygen species (ROS), finally triggering the release of many damage-associated molecular patterns (DAMPs). Moreover, the MB@OVA/PPY NPs synergized with DAMPs to promote the maturation and improve the antigen presentation ability of DCs in vitro and in vivo. CONCLUSIONS: This work reported a PPY NPs-based nanoplatform to encapsulate the therepeutic proteins and absorb the functional molecules for combination therapy of tumours. The results demonstrated that the prepared MB@OVA/PPY NPs could be used as effective nanotherapeutic agents to eliminate solid tumours and trigger a powerful antitumour immune response.

Polypyrrole-Gold nanocomposites as a promising photothermal agent: Preparation, characterization and cytotoxicity study.

Photothermal nanomaterials with near-infrared absorption and high energy conversion efficiency have recently attracted significant interest. Polypyrrole-gold nanocomposites (PPy-Au NCs) as photothermal nanoagents are synthesized using ex-situ polymerization method of the modified pyrrole monomers. Microscopic and spectroscopic characterization techniques are used to reveal the surface structure, composition variation and photoelectric properties of PPy-Au NCs, gold nanorods (Au NRs) and polypyyrole nanoparticles (PPy NPs). Their cytotoxic effects on the viability of Ehrlich Ascites Carcinoma cells in the dark are demonstrated. The surface coating of Au NRs with PPy NPs shows an enhancement in the photothermal efficiency of the proposed photothermal nanoagent. The photothermal conversion of nanomaterials are examined using polarized polychromatic incoherent low-energy light source (the energy density of the light is 2.4 J/cm2 per minute and the specific power density is 40 mW/cm2).

(Rose Bengal)/(Eosin Yellow)-Gold-Polypyrrole Hybrids: A Design for Dual Photo-Active Nano-System with Ultra-High Loading Capacity.

PURPOSE: Enhancement of the photodynamic/photothermal efficiency of two water-soluble dyes, rose bengal (RB) and eosin yellow (EY), via conjugation to a polymeric nano-system gold-polypyrrole nanoparticle (AuPpy NPs). METHODOLOGY: A multi-step synthesis method and an in situ one-pot synthesis method were used. Loading percentage, particle size, zeta potential, morphology, UV-Vis-NIR spectrophotometry and in vitro photothermal activity were measured. Then, both hybrid nanocomposites were examined for their cytotoxicity and photocytotoxicity on HepG2 cell line as a model for cancer cells. RESULTS: Dyes loaded in the traditional multi-step method did not exceed 9% w/w, while in the one-pot synthesis method they reached ~67% w/w and ~75% w/w for EY-AuPpy NPs and RB-AuPpy NPs, respectively. UV-Vis-NIR spectrophotometry showed that both nano-systems exhibited intense absorption in the NIR region. The mean size of the nanoparticles was ~31.5 nm (RB-AuPpy NPs) and ~33.6 nm (EY-AuPpy NPs) with zeta potential values of -26.5 mV and -33 mV, respectively. TEM imaging revealed the morphology of both hybrids, showing ultra-nano spherical-shaped gold cores in the case of RB-AuPpy NPs, and different shapes of larger gold cores in the case of EY-AuPpy NPs, both embedded in the polymer film. Conjugation to AuPpy was found to significantly reduce the dark cytotoxicity of both RB and EY, preserving the photocytotoxicity of EY and enhancing the photocytotoxicity of RB. CONCLUSION: Gold-polypyrrole nanoparticles represent an effective delivery system to improve the photodynamic and photothermal properties of RB and EY. The in situ one-pot synthesis method provided a means to greatly increase the loading capacity of AuPpy NPs. While both hybrid nanocomposites exhibited greatly diminished dark cytotoxicity, RB-AuPpy NPs showed significantly enhanced photocytotoxicity compared to the free dyes. This pattern enables the safe use of both dyes in high concentrations with sustained action, reducing dose frequency and side effects.

MoS2/PPy Nanocomposite as a Transducer for Electrochemical Aptasensor of Ampicillin in River Water.

We report the design of an electrochemical aptasensor for ampicillin detection, which is an antibiotic widely used in agriculture and considered to be a water contaminant. We studied the transducing potential of nanostructure composed of MoS2 nanosheets and conductive polypyrrole nanoparticles (PPyNPs) cast on a screen-printed electrode. Fine chemistry is developed to build the biosensors entirely based on robust covalent immobilizations of naphthoquinone as a redox marker and the aptamer. The structural and morphological properties of the nanocomposite were studied by SEM, AFM, and FT-IR. High-resolution XPS measurements demonstrated the formation of a binding between the two nanomaterials and energy transfer affording the formation of heterostructure. Cyclic voltammetry and electrochemical impedance spectroscopy were used to analyze their electrocatalytic properties. We demonstrated that the nanocomposite formed with PPyNPs and MoS2 nanosheets has electro-catalytic properties and conductivity leading to a synergetic effect on the electrochemical redox process of the redox marker. Thus, a highly sensitive redox process was obtained that could follow the recognition process between the apatamer and the target. An amperometric variation of the naphthoquinone response was obtained regarding the ampicillin concentration with a limit of detection (LOD) of 10 pg/L (0.28 pM). A high selectivity towards other contaminants was demonstrated with this biosensor and the analysis of real river water samples without any treatment showed good recovery results thanks to the antifouling properties. This biosensor can be considered a promising device for the detection of antibiotics in the environment as a point-of-use system.

Safety Assessment of Polypyrrole Nanoparticles and Spray-Coated Textiles.

Polypyrrole (PPy) nanoparticles (NPs) are used for the coating of materials, such as textiles, with biomedical applications, including wound care and tissue engineering, but they are also promising antibacterial agents. In this work, PPy NPs were used for the spray-coating of textiles with antimicrobial properties. The functional properties of the materials were verified, and their safety was evaluated. Two main exposure scenarios for humans were identified: inhalation of PPy NPs during spray (manufacturing) and direct skin contact with NPs-coated fabrics (use). Thus, the toxicity properties of PPy NPs and PPy-coated textiles were assessed by using in vitro models representative of the lung and the skin. The results from the materials' characterization showed the stability of both the PPy NP suspension and the textile coating, even after washing cycles and extraction in artificial sweat. Data from an in vitro model of the air-blood barrier showed the low toxicity of these NPs, with no alteration of cell viability and functionality observed. The skin toxicity of PPy NPs and the coated textiles was assessed on a reconstructed human epidermis model following OECD 431 and 439 guidelines. PPy NPs proved to be non-corrosive at the tested conditions, as well as non-irritant after extraction in artificial sweat at two different pH conditions. The obtained data suggest that PPy NPs are safe NMs in applications for textile coating.

Graphene Loading with Polypyrrole Nanoparticles for Trace-Level Detection of Ammonia at Room Temperature.

The outstanding versatility of graphene for surface functionalization has been exploited by its decoration with synthesized polypyrrole (PPy) nanoparticles (NPs). A green, facile, and easily scalable for mass production nanocomposite development was proposed, and the resulting PPy@Graphene was implemented in chemoresistive gas sensors able to detect trace levels of ammonia (NH3) under room-temperature conditions. Gas exposure for 5 min revealed that the presence of nanoparticles decorating graphene entail greater sensitivity (13-fold) in comparison to the bare graphene performance. Noteworthy, excellent repeatability (0.7% of relative error) and a low limit of detection of 491 ppb were obtained, together with excellent long-term stability. Besides, an extensive material characterization was conducted, and vibration bands obtained via Raman spectroscopy confirmed the formation of PPy NPs, while X-ray spectroscopy (XPS) revealed the relative abundance of the different species, as polarons and bipolarons. Additionally, XPS analyses were conducted before and after NH3 exposure to assess the PPy aging and the changes induced in their physicochemical and electronic properties. Specifically, the gas sensor was tested during a 5-month period, demonstrating significant stability over time, since just a slight decrease (11%) in the responses was registered. In summary, the present work reports for the first time the use of PPy NPs decorating graphene for gas-sensing purposes, revealing promising properties for the development of unattended gas-sensing networks for monitoring air quality.

Polypyrrole-Based Nanorobots Powered by Light and Glucose for Pollutant Degradation in Water.

Novel photoactive and enzymatically active nanomotors were developed for efficient organic pollutant degradation. The developed preparation route is simple and scalable. Light-absorbing polypyrrole nanoparticles were equipped with a bi-enzyme [glucose oxidase/catalase (GOx/Cat)] system enabling the simultaneous utilization of light and glucose as energy sources for jet-induced nanoparticle movement and active radical production. The GOx utilizes glucose to produce hydrogen peroxide, which is subsequently degraded by Cat, resulting in the generation of active radicals and/or oxygen bubbles that propel the particles. Uneven grafting of GOx/Cat molecules on the nanoparticle surface ensures inhomogeneity of peroxide creation/degradation, providing the nanomotor random propelling. The nanomotors were tested for their ability to degrade chlorophenol, under various experimental conditions, that is, with and without simulated sunlight illumination or glucose addition. In all cases, degradation was accelerated by the presence of the self-propelled nanoparticles or light illumination. Light-induced heating also positively affects enzymatic activity, further accelerating nanomotor diffusion and pollutant degradation. In fact, the chemical and photoactivities of the nanoparticles led to more than 95% removal of chlorophenol in 1 h, without any external stirring. Finally, the quality of the purified water and the extent of pollutant removal were checked using an eco-toxicological assay, with demonstrated significant synergy between glucose pumping and sunlight illumination.

Enhanced anticancer effect of ROS-boosted photothermal therapy by using fucoidan-coated polypyrrole nanoparticles.

Nanomaterial mediated cancer/tumor photo driven hyperthermia has obtained great awareness. Nevertheless, it is a challenge for improving the hyperthermic efficacy lacking resistance to stimulated thermal stress. We thus developed a bioinspired nano-platform utilizing inclusion complexation between photosensitive polypyrrole (Ppy) nanoparticles (NP) and fucoidan (FU). This FU-Ppy NP proved to be an excellent P-selectin-mediated, lung cancer-cell/tumor targeting delivery and specific accumulation, could augment cancer/tumor oxidative stress levels through producing cellular reactive oxygen species. Potent ROS/photothermal combinational therapeutic effects were exhibited by the bioinspired FU-Ppy NP through a selective P-selectin cancer/tumor targeting aptitude for the lung cancer cells/tumor compared with other nano-formulations. The usage of FU-Ppy NP also involves the potential mechanism of suppressing the biological expression of tumor vascular endothelial growth factor (VEGF). This FU biological macromolecule-amplified photothermally therapeutic nano-platform has promising potential for future medical translation in eradicating numerous tumors.

Novel Semi-Interpenetrated Polymer Networks of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)/Poly (Vinyl Alcohol) with Incorporated Conductive Polypyrrole Nanoparticles.

This paper reports the preparation and characterization of semi-interpenetrating polymer networks (semi-IPN) of poly(3-hydroxybutirate-co-3-hydroxyvalerate), PHBV, and poly (vinyl alcohol), PVA, with conductive polypirrole (PPy) nanoparticles. Stable hybrid semi-IPN (PHBV/PVA 30/70 ratio) hydrogels were produced by solvent casting, dissolving each polymer in chloroform and 1-methyl-2-pyrrolidone respectively, and subsequent glutaraldehyde crosslinking of the PVA chains. The microstructure and physical properties of this novel polymeric system were analysed, including thermal behaviour and degradation, water sorption, wettability and electrical conductivity. The conductivity of these advanced networks rose significantly at higher PPy nanoparticles content. Fourier transform infrared spectroscopy (FTIR) and calorimetry characterization indicated good miscibility and compatibility between all the constituents, with no phase separation and strong interactions between phases. A single glass transition was observed between those of pure PHBV and PVA, although PVA was dominant in its contribution to the glass transition process. Incorporating PPy nanoparticles significantly reduced the hydrogel swelling, even at low concentrations, indicating molecular interactions between the PPy nanoparticles and the hydrogel matrix. The PHBV/PVA semi-IPN showed higher thermal stability than the neat polymers and PHBV/PVA blend, which also remained in the tertiary systems.

On-Site Colorimetric Detection of Cholesterol Based on Polypyrrole Nanoparticles.

Herein, we report a facile method for cholesterol detection by coupling the peroxidase-like activity of polypyrrole nanoparticles (PPy NPs) and cholesterol oxidase (ChOx). ChOx can catalyze the oxidation of cholesterol to produce H2O2. Subsequently, PPy NPs, as a nanozyme, induce the reaction between H2O2 and 3,3',5,5'-tetramethylbenzidine (TMB). Under optimal conditions, the increase is proportional to cholesterol with concentrations from 10 to 800 µM in absorbance of TMB at 652 nm. The linear range for cholesterol is 10-100 µM, with a detection limit of 3.5 µM. This reported method is successfully employed for detection of cholesterol in human serum. The recovery percentage is ranged within 96-106.9%. Furthermore, we designed a facile and simple portable assay kit using the proposed system, realizing the on-site semiquantitative and visual detection of cholesterol in human serum. The cholesterol content detected from the portable assay kit were closely matching those obtained results from solution-based assays, thereby holding great potential in clinical diagnosis and health management.

A Label-Free Fluorescent Aptasensor for Detection of Staphylococcal Enterotoxin A Based on Aptamer-Functionalized Silver Nanoclusters.

Staphylococcal enterotoxin A (SEA) is a worldwide public health problem accounting for the majority of food poisoning which is produced by Staphylococcus aureus, threatening human health and leading to various foodborne diseases. Therefore, it is of great significance to develop a sensitive detection method for SEA to ensure food safety and prevent foodborne diseases in humans. In this study, an adaptive fluorescence biosensor for the detection of staphylococcal enterotoxin A (SEA) was designed and developed by combining DNA silver nanoclusters (DNA-AgNCs) with polypyrrole nanoparticles (PPyNPs). Fluorescent AgNCs, synthesized using aptamers as templates, were used as fluorescence probes, whose fluorescence was quenched by PPyNPs. In the presence of the target SEA, DNA-AgNCs were forced to desorb from the surface of PPyNPs through the binding of SEA with the aptamer-DNA-AgNCs, thereby resulting in fluorescence recovery. Under the optimized conditions, the relative fluorescence intensity (FI) showed a linear relationship with the SEA concentration in the range from 0.5 to 1000 ng/mL (Y = 1.4917X + 0.9100, R2 = 0.9948) with a limit of detection (LOD) of 0.3393 ng/mL. The sensor was successfully used to evaluate the content of SEA in milk samples, and the recovery efficiency of SEA was between 87.70% and 94.65%. Thus, the sensor shows great potential for application in food analysis. In short, the proposed platform consisted of an aptamer fluorescent sensor that can be used for the ultrasensitive detection of various toxins by taking advantage of the excellent affinity and specificity of corresponding aptamers.