Targeted Delivery of Peptide Nucleic Acid by Biomimetic Nanoparticles Based on Extracellular Vesicle-coated Mesoporous Silica Nanoparticles.

BACKGROUND: Peptide nucleic acid (PNA) plays an important role in antimicrobial activity, but its cellular permeability is poor. To overcome this limitation, we constructed biomimetic nanoparticles by using extracellular vesicle (EV)-coated mesoporous silicon nanoparticles (MSNs) to deliver PNA to Staphylococcus aureus (S. aureus) and improve its antisense therapeutic effect. METHOD: MSN was prepared by the sol-gel method, and EV was extracted by affinity resin chromatography. EV was coated on MSN by simple sonication (50 W, 3 min) to prepare biomimetic nanoparticles with PNA-loaded MSN as the core and EV isolated from S. aureus as the shell. RESULTS: The MSN prepared by the sol-gel method had a uniform particle size (100 nm) and well-defined pore size for loading PNA with good encapsulation efficiency (62.92%) and drug loading (7.74%). The concentration of EV extracted by affinity resin chromatography was about 1.74 mg/mL. EV could be well coated on MSN through simple ultrasonic treatment (50 W, 3 min), and the stability and blood compatibility of MSN@ EV were good. Internalization experiments showed that EV could selectively enhance the uptake of biomimetic nanoparticles by S. aureus. Preliminary in vitro antibacterial tests revealed that PNA@MSN@EV exhibited enhanced antibacterial activity against S. aureus and had stronger bactericidal activity than free PNA and PNA@MSN at equivalent PNA concentrations (8 µM). CONCLUSION: Biomimetic nanoparticles based on EV-coated MSN offer a new strategy to improve the efficacy of PNA for the treatment of bacterial infections, and the technology holds promise for extension to the delivery of antibiotics that are traditionally minimally effective or prone to resistance.

Three-Dimensional Electrochemical Sensors for Food Safety Applications.

Considering the increasing concern for food safety, electrochemical methods for detecting specific ingredients in the food are currently the most efficient method due to their low cost, fast response signal, high sensitivity, and ease of use. The detection efficiency of electrochemical sensors is determined by the electrode materials' electrochemical characteristics. Among them, three-dimensional (3D) electrodes have unique advantages in electronic transfer, adsorption capacity and exposure of active sites for energy storage, novel materials, and electrochemical sensing. Therefore, this review begins by outlining the benefits and drawbacks of 3D electrodes compared to other materials before going into more detail about how 3D materials are synthesized. Next, different types of 3D electrodes are outlined together with common modification techniques for enhancing electrochemical performance. After this, a demonstration of 3D electrochemical sensors for food safety applications, such as detecting components, additives, emerging pollutants, and bacteria in food, was given. Finally, improvement measures and development directions of electrodes with 3D electrochemical sensors are discussed. We think that this review will help with the creation of new 3D electrodes and offer fresh perspectives on how to achieve extremely sensitive electrochemical detection in the area of food safety.

Advances in Portable Heavy Metal Ion Sensors.

Heavy metal ions, one of the major pollutants in the environment, exhibit non-degradable and bio-chain accumulation characteristics, seriously damage the environment, and threaten human health. Traditional heavy metal ion detection methods often require complex and expensive instruments, professional operation, tedious sample preparation, high requirements for laboratory conditions, and operator professionalism, and they cannot be widely used in the field for real-time and rapid detection. Therefore, developing portable, highly sensitive, selective, and economical sensors is necessary for the detection of toxic metal ions in the field. This paper presents portable sensing based on optical and electrochemical methods for the in situ detection of trace heavy metal ions. Progress in research on portable sensor devices based on fluorescence, colorimetric, portable surface Raman enhancement, plasmon resonance, and various electrical parameter analysis principles is highlighted, and the characteristics of the detection limits, linear detection ranges, and stability of the various sensing methods are analyzed. Accordingly, this review provides a reference for the design of portable heavy metal ion sensing.

DPP-Cu2+ Complexes Gated Mesoporous Silica Nanoparticles For pH and Redox Dual Stimuli-Responsive Drug Delivery.

OBJECTIVE: A simple pH and redox dual stimuli-responsive diketopyrrolopyrrole (DPP)-Cu2+ complexes gated mesoporous silica nanoparticles (MSN) were prepared for precise drug delivery and controlled drug release. METHOD: MSN was prepared by sol-gel method and then laminated. Carboxylic acid (CA)-Pyrrolo[3,4-c] pyrrole-1,4-dione, 2,5-dihydro-3,6-di-2-pyridinyl (PyDPP) was grafted onto the surface of amino-functionalized MSN (MSN-NH2) through a simple amide reaction and then complexed with Cu2+ to form gated molecules after doxorubicin (DOX) loading. RESULTS: Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Low-angle X-ray diffraction (XRD) showed that MSN with uniform particle size (100 nm) and porous structure was successfully prepared. The prepared MSN, MSN- NH2, and MSN-DPP were fully characterized by Zeta potential, Fourier transforms infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption- desorption. High DOX-loading capacity (18.22%) and encapsulation efficiency (89.16%) were achieved by optimizing the mass ratio of MSN to DOX. Release studies showed that the gated molecules of our designed DPP-Cu2+ complexes had a good blocking effect under physiological conditions (the cumulative release rate of drugs within 24 hours was only 4.18%) and responded well to the pH and redox glutathione (GSH) dual stimuli. In vitro cytotoxicity assay showed that MSN-DPP-Cu2+ had good biocompatibility in both Hep G2 cells and L02 cells (the relative cell viability of both cells within 48 hours was above 97%), and the MSN-DPP-Cu2+@DOX could be triggered for efficient drug release in Hep G2 cells. CONCLUSION: The MSN-DPP-Cu2+ described in this research may be a good delivery system for the controlled release of antitumor drugs and can provide a potential possibility for clinical application in the future.

Multiple amplification-based fluorometric aptasensor for highly sensitive detection of Staphylococcus aureus.

Rapid and accurate detection and identification of Staphylococcus aureus (S. aureus) are of great significance for food safety, environmental monitoring, early clinical diagnosis, and prevention of the spread of drug-resistant bacteria. Herein, we design a fluorometric aptasensor for ultra-sensitive, specific, and rapid detection of S. aureus. The apasensor combines the enrichment and separation of magnetic nanoparticles (MNPs), the biotin-streptavidin conjugation system, and a single S. aureus can release four signaling probes for signal amplification. Aptamer acts as a specific biorecognition element of S. aureus. Four FAM-labeled partially complementary sequences (FAM-pcDNAs) were used as signaling probes. The aptamers were sequential hybridized with the four FAM-pcDNAs to form aptamer&pcDNAs, which were then bound to MNPs via the biotin-streptavidin. When the aptamer specifically recognizes and binds to S. aureus, the FAM-pcDNAs signaling probes are replaced and released into the supernatant. The concentration of S. aureus can be quantified by measuring the fluorescence intensity (λexc/em = 492/520 nm) of the replaced signaling probe FAM-pcDNAs. The results show that the proposed fluorometric aptasensor displays good specificity, ultra-high sensitivity (1.23 cfu/mL), wide linear range (1 ~ 108 cfu/mL), and fast detection speed (~ 1.5 h). The recovery test verifies further that the proposed fluorometric aptasensor can detect S. aureus in spiked blood samples. Since aptamers are easy to customize, we believe that fluorometric aptasensors based on multiple amplification have broad prospects in the construction of practical high-performance biosensors for bacterial detection. KEY POINTS: • Multiple amplification-based fluorometric aptasensor for S. aureus is developed • The aptasensor displays high specificity with a LOD of 1.23 CFU/mL • The aptasensor can directly detect S. aureus in spiked blood samples.

Recent Advances in Aptasensors For Rapid and Sensitive Detection of Staphylococcus Aureus.

The infection of Staphylococcus aureus (S.aureus) and the spread of drug-resistant bacteria pose a serious threat to global public health. Therefore, timely, rapid and accurate detection of S. aureus is of great significance for food safety, environmental monitoring, clinical diagnosis and treatment, and prevention of drug-resistant bacteria dissemination. Traditional S. aureus detection methods such as culture identification, ELISA, PCR, MALDI-TOF-MS and sequencing, etc., have good sensitivity and specificity, but they are complex to operate, requiring professionals and expensive and complex machines. Therefore, it is still challenging to develop a fast, simple, low-cost, specific and sensitive S. aureus detection method. Recent studies have demonstrated that fast, specific, low-cost, low sample volume, automated, and portable aptasensors have been widely used for S. aureus detection and have been proposed as the most attractive alternatives to their traditional detection methods. In this review, recent advances of aptasensors based on different transducer (optical and electrochemical) for S. aureus detection have been discussed in details. Furthermore, the applications of aptasensors in point-of-care testing (POCT) have also been discussed. More and more aptasensors are combined with nanomaterials as efficient transducers and amplifiers, which appears to be the development trend in aptasensors. Finally, some significant challenges for the development and application of aptasensors are outlined.

Application strategies of peptide nucleic acids toward electrochemical nucleic acid sensors.

Peptide nucleic acids (PNAs) have attracted tremendous interest in the fabrication of highly sensitive electrochemical nucleic acid biosensors due to their higher stability and increased sensitivity than common DNA probes. The neutral pseudopeptide backbone of PNAs not only makes the PNA/DNA duplexes more stable but also provides many opportunities to construct ultrasensitive nucleic acid sensors. This review presents the details of various protocols for the construction of PNA-based electrochemical nucleic acid sensors. The crucial factors, origin, and development of PNA, immobilization methods of PNA probes and signal generation mechanisms, are discussed. This review aims to provide a reference for ultrasensitive PNA electrochemical biosensor preparation.