Addressing Water Contamination and Associated Health Issues through Community-Based Interventions: A Case Study in Khon Kaen Province.

A recent study conducted in Khon Kaen Province, Thailand, evaluated the effectiveness of a technology-assisted intervention aimed at improving water quality and addressing related health issues in communities around key water bodies. The intervention targeted health concerns associated with water contamination, including chronic kidney diseases, skin conditions, hypertension, and neurological symptoms. The study included water quality assessments and health evaluations of 586 residents and implemented a Learning Innovation Platform (LIP) across 13 communities. Results showed significant improvements in the community, including a decrease in hypertension and skin-related health issues, as well as enhanced community awareness and proficiency in implementing simple water quality assessments and treatment. The study demonstrated the value of a comprehensive, technology-driven community approach, effectively enhancing water quality and health outcomes, and promoting greater community awareness and self-sufficiency in managing environmental health risks.

Characterizing a visual lateral flow device for rapid SARS-CoV-2 virus protein detection: pre-clinical and system assessment.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infections have affected more than 769 million individuals worldwide over the last few years. Although the pandemic is transitioning into an endemic, the COVID-19 outbreak is still a global concern. A rapid screening platform is needed for effective preventive and control measures. Herein, a visual rapid lateral flow platform for SARS-CoV-2 nucleocapsid protein detection is developed. Under optimal conditions, the system demonstrated good detection sensitivity and selectivity against tested respiratory viruses. The system provides direct visual detection with a limit of 0.7 ng of the nucleocapsid protein per mL of a sample (0.7 ng mL-1) within 15 minutes. Further, a correlation between direct visual detection and semi-quantitative analysis using a reader showed a similar detection limit (R2 = 0.9571). The repeatability and reproducibility studies highlighted the potential of the system for the rapid screening of SARS-CoV-2 infection, with variations within 5% and 10% at high and low protein concentrations, respectively. Subsequent pre-clinical validation to correlate the performance with the standard molecular approach (RT-PCR) using 170 nasopharyngeal swabs demonstrated 98% estimated sensitivity (95% CI, 89.35-99.95%) and 100% specificity (95% CI, 96.38-100%). The positive and negative predictive values were reported to be 100% and 99%, respectively, with an accuracy of 99.3%. With high viral load samples (Ct value ≤25, n = 47), the system demonstrated 100% detection sensitivity and specificity. The proposed technique provides a valuable platform for potential use in rapid screening, particularly during pandemics, where diagnostic capacity and mass screening are crucial.

Layer-by-Layer Biopolymer Assembly for the In Situ Fabrication of AuNP Plasmonic Paper-A SERS Substrate for Food Adulteration Detection.

Here, we introduce an environmentally friendly approach to fabricate a simple and cost-effective plasmonic paper for detecting food additives using surface-enhanced Raman spectroscopy (SERS). The plasmonic paper is fabricated by in situ growth of gold nanoparticles (AuNPs) on filter paper (FP). To facilitate this green fabrication process, we applied a double-layered coating of biopolymers, chitosan (CS) and alginate (ALG), onto the FP using a layer-by-layer (LbL) assembly through electrostatic interactions. Compared to single-layer biopolymer coatings, double-layered biopolymer-coated paper, ALG/CS/FP, significantly improves the reduction properties. Consequently, effective in situ growth of AuNPs can be achieved as seen in high density of AuNP formation on the substrate. The resulting plasmonic paper provides high SERS performance with an enhancement factor (EF) of 5.7 × 1010 and a low limit of detection (LOD) as low as 1.37 × 10-12 M 4-mercaptobenzoic acid (4-MBA). Furthermore, it exhibits spot-to-spot reproducibility with a relative standard deviation (RSD) of 8.2% for SERS analysis and long-term stability over 50 days. This paper-based SERS substrate is applied for melamine (MEL) detection with a low detection limit of 0.2 ppb, which is sufficient for monitoring MEL contamination in milk based on food regulations. Additionally, we demonstrate a simultaneous detection of ß-agonists, including ractopamine (RAC) and salbutamol (SAL), exhibiting the multiplexing capability and versatility of the plasmonic paper in food contaminant analysis. The development of this simple plasmonic paper through the LbL biopolymer assembly not only paves the way for novel SERS substrate fabrication but also broadens the application of SERS technology in food contaminant monitoring.

A toluidine blue/porous organic polymer/2D MoSe2 nanocomposite as an electrochemical signaling platform for a sensitive label-free aflatoxin B1 bioassay in some crops.

A label-free electrochemical immunosensor using a toluidine blue (TB)/porous organic polymer (POP)/two-dimensional molybdenum diselenide (2D MoSe2) nanocomposite is developed for highly sensitive detection of aflatoxin B1 (AFB1) in selected crops. A POP/2D MoSe2 composite material is employed to modify the surface of a screen-printed carbon electrode (SPCE). Subsequently, TB is adsorbed on the modified SPCE surface, and the resulting TB/POP/2D MoSe2 composite is then used to construct a biosensor. The new POP/2D MoSe2 nanocomposite offers a high surface-to-volume area and is a good electroactive and biocompatible adsorbent for loading TB probe and capture antibodies. Adsorbed TB onto the POP/2D MoSe2 nanocomposite is utilized as a redox probe for the signal amplification unit. This TB/POP/2D MoSe2 nanocomposite provides good electron transfer properties of TB redox probe, good electrical conductivity, good biocompatibility, and likable adsorption ability, thus obtaining a sufficient immobilization quantity of antibodies for the sensor construction. After immobilization of the anti-AFB1 antibody and blocking with BSA on the composite surface, the immunosensor is obtained for the detection of AFB1. Under optimum conditions, the sensor shows a linear logarithmic range of 2.5-40 ng mL-1 with a limit of detection (LOD) of 0.40 ng mL-1. The developed sensor provides several advantages in terms of simplicity, low cost, short analysis time, high selectivity, stability, and reproducibility. Additionally, the proposed immunosensor is successfully validated by the detection of AFB1 in rice, corn, and peanut samples. Utilizing the TB/POP/2D MoSe2 nanocomposite, this label-free electrochemical immunosensor demonstrates outstanding sensitivity and selectivity in detecting AFB1, making it a valuable tool for ensuring the safety of agricultural products and enhancing food security.

A new portable toluidine blue/aptamer complex-on-polyethyleneimine-coated gold nanoparticles-based sensor for label-free electrochemical detection of alpha-fetoprotein.

The quantification of alpha-fetoprotein (AFP) as a potential liver cancer biomarker which is generally found in ultratrace level is of significance in biomedical diagnostics. Therefore, it is challenging to find a strategy to fabricate a highly sensitive electrochemical device towards AFP detection through electrode modification for signal generation and amplification. This work shows the construction of a simple, reliable, highly sensitive, and label-free aptasensor based on polyethyleneimine-coated gold nanoparticles (PEI-AuNPs). A disposable ItalSens screen-printed electrode (SPE) is employed for fabricating the sensor by successive modifying with PEI-AuNPs, aptamer, bovine serum albumin (BSA), and toluidine blue (TB), respectively. The AFP assay is easily performed when the electrode is inserted into a small Sensit/Smart potentiostat connected to a smartphone. The readout signal of the aptasensor derives from the electrochemical response of TB intercalating into the aptamer-modified electrode after binding with the target. The decrease in current response of the proposed sensor is proportional to the AFP concentration due to the restriction of the electron transfer pathway of TB by a number of insulating AFP/aptamer complexes on the electrode surface. PEI-AuNPs improve SPE's reactivity and provide a large surface area for aptamer immobilization whereas aptamer provides selectivity to the target AFP. Consequently, this electrochemical biosensor is highly sensitive and selective for AFP analysis. The developed assay reveals a linear range of detection from 10 to 50000 pg mL-1 with R 2 = 0.9977 and provided a limit of detection (LOD) of 9.5 pg mL-1 in human serum. With its simplicity and robustness, it is anticipated that this electrochemical-based aptasensor will be a benefit for the clinical diagnosis of liver cancer and further developed for other biomarkers analysis.

Fabrication of paper-based SERS substrate using a simple vacuum filtration system for pesticides detection.

Herein, we describe a simple and cost-effective fabrication of a paper-based SERS substrate by coating poly(diallyldimethylammonium chloride) (PDADMAC) and gold nanostars (AuNSs) on the filter paper using a vacuum filtration system. The paper-based SERS substrates were fabricated and ready to be used within an hour without any complicated equipment or processes. The cationic polymer, PDADAMAC, was pretreated on the filter paper to improve the absorbability of negatively charged AuNSs through electrostatic interaction. The PDADMAC/AuNS paper significantly intensified the SERS signal of 4-mercaptobenzoic acid (4-MBA) compared to that of pure AuNS-coated paper due to the high density of AuNSs absorbed on the SERS substrate. The PDADMAC/AuNS paper substrate provided a SERS enhancement factor (EF) of 1.08 × 107 with a low detection limit of 1 nM 4-MBA. The substrate shows excellent spot-to-spot reproducibility with a relative standard deviation (RSD) of 5.03%, and substrate-to-substrate reproducibility with an RSD of 3.20% for the Raman shift at 1080 cm-1. The paper substrate was then applied for the rapid detection of pesticides with a low detection limit of 0.51 µM (0.13 ppm) for paraquat, and 0.38 µM (0.09 ppm) for thiram, using a handheld Raman spectrometer. The development of this simple and cost-effective paper-based SERS substrate, and its applications for on-site monitoring of pesticides, could be beneficial for food security and environmental safety.

Detection of a miRNA biomarker for cancer diagnosis using SERS tags and magnetic separation.

Detection of miR-29a, a biomarker of cancers, using SERS tags and magnetic separation is described. The assay was designed to detect the miR-29a sequence by taking the complementary sequence and splitting it into a capture and detection probe. The SERS tags comprised the highly Raman active molecule 4-mercaptobenzoic acid (4-MBA) and DNA detection probes assembled onto the surface of gold nanorods (AuNRs) through the self-assembly process. The capture DNA conjugated magnetic nanoparticles (MNPs) were applied as capture probes. The detection was based on the hybridisation and sandwich complex formation. The resultant hybridisation-dependent complexes were recovered and enriched from the samples by magnetic separation. The enriched solution containing target miRNA hybridised with capture probes were dropped on a foil-covered slide to form a droplet for SERS analysis. A characteristic spectrum of 4-MBA was observed to indicate the presence of the miR-29a in the samples. The sensitivity of the assay is examined by measuring the SERS signal of the samples containing different concentrations of the miR-29a. The SERS intensity appears to increase with the concentration of miR-29a. The limit of detection (LOD) was found to be 10 pM without any amplification process. In addition, the selectivity and feasibility of the assay in complex media are evaluated with the non-target miRNAs comprising different sequences from the target miR-29a. The system was capable of detecting the target miR-29a specifically with high selectivity. These results suggest that this solution-based SERS platform has a significant capability for simple, sensitive, and selective miR-29a analysis.

A gold nanoparticle-dye/poly(3-aminobenzylamine)/two dimensional MoSe2/graphene oxide electrode towards label-free electrochemical biosensor for simultaneous dual-mode detection of cancer antigen 15-3 and microRNA-21.

A dual-mode electrochemical biosensor is successfully developed for simultaneous detection of two different kinds of breast cancer biomarkers, namely cancer antigen 15-3 (CA 15-3) and microRNA-21 (miRNA-21), for the first time. The sensor composes of a poly(3-aminobenzylamine)/two-dimensional (2D) molybdenum selenide/graphene oxide nanocomposite modified two-screen-printed carbon electrode array (dual electrode), functionalized individually with 2,3-diaminophenazine-gold nanoparticles and toluidine blue-gold nanoparticles. Both kinds of the redox probe-gold nanoparticles are employed as signaling molecules and supports for immobilization of anti-CA 15-3 antibodies and capture DNA-21 probes, respectively. Due to the good conductivity and high surface-to-volume ratio of the nanocomposite, high amount of the antibodies and capture probes can be immobilized on the modified dual-electrode, giving the efficient duplex detection. Consequently, the biosensor provides good selectivity, and high sensitivity for the dual target analyte detection. The experimental results show that this label-free biosensor exhibits good linear responses to the concentrations of both target analytes with the limits of detection (LODs) of 0.14 U mL-1 and 1.2 fM for CA 15-3 and miRNA-21, respectively. This assay strategy has a great potential to be further developed for the simultaneous detection of a variety of miRNAs and protein biomarkers for point-of-care (POC) diagnostic applications.

Electrochemical detection of matrix metalloproteinase-7 using an immunoassay on a methylene blue/2D MoS2/graphene oxide electrode.

Methylene blue (MB) adsorption onto a two-dimensional molybdenum disulfide (2D MoS2)/graphene oxide (GO) nanocomposite sitting on a screen-printed carbon electrode (SPCE) is used to develop a new sensitive label-free electrochemical immunosensor for the detection of matrix metalloproteinase-7 (MMP-7) cancer biomarkers. The 2D MoS2/GO nanocomposite deposited onto an SPCE provides a large specific surface area, fast electron transfer, and exceptional electrical conductivity. Furthermore, MB adsorbed onto the 2D MoS2/GO nanocomposite architecture can be used for signal amplification in electrochemical immunosensors. Moreover, an immunosensor platform was fabricated by the adsorption of anti-MMP-7 capture antibodies onto the MB/2D MoS2/GO nanocomposite surface via electrostatic interactions for the detection of the MMP-7 immunocomplex. Under optimum conditions, the label-free immunosensor exhibits a decrease in the current response for MB corresponding to the MMP-7 concentration. The sensor affords a linear logarithmic range of 0.010-75 ng mL-1 with a limit of detection (LOD) of 0.007 ng mL-1. The developed electrochemical immunosensor provides high selectivity, good reproducibility, and excellent stability. Furthermore, the proposed immunosensor can be applied for the detection of MMP-7 in human serum samples with good recovery. Thus, this device can be applied for the early clinical diagnosis of pancreatic and colorectal cancers.

An electrochemical biosensor for simultaneous detection of breast cancer clinically related microRNAs based on a gold nanoparticles/graphene quantum dots/graphene oxide film.

A label-free multiplexed electrochemical biosensor based on a gold nanoparticles/graphene quantum dots/graphene oxide (AuNPs/GQDs/GO) modified three-screen-printed carbon electrode (3SPCE) array is successfully constructed to detect miRNA-21, miRNA-155, and miRNA-210 biomarkers for the first time. Redox species (anthraquinone (AQ), methylene blue (MB), and polydopamine (PDA)) are used as redox indicators for anchoring capture miRNA probes, which hybridize with the complementary targets, miRNA-21, miRNA-155, and miRNA-210, respectively. After three target miRNAs are present, the square wave voltammetry (SWV) scan displays three well-separated peaks. Each peak indicates the presence of one miRNA, and its intensity quantitatively correlates with the concentration of the corresponding target analyte. This phenomenon results in the substantial decline of the SWV peak current of the redox probes. The developed AuNPs/GQDs/GO-based biosensor reveals excellent performance for simultaneous miRNA sensing. It offers a wide linear dynamic range from 0.001 to 1000 pM with ultrasensitive low detection limits of 0.04, 0.33, and 0.28 fM for the detection of miRNA-21, miRNA-155, and miRNA-210, respectively. It also presents high selectivity and applicability for the detection of miRNAs in human serum samples. This multiplex label-free miRNA biosensor has great potential for applications in breast cancer diagnosis.

A simple fluorescence-based lateral flow test platform for rapid influenza B virus screening.

A simple fluorescence-based lateral flow test platform for rapid influenza B virus screening as a model target molecule was successfully developed. In this work, Cy5-loaded silica nanoparticles were directly conjugated to monoclonal antibodies, specific to the influenza B nucleoprotein, via a direct physisorption method and used as detector probes. Using this approach, the signal response to the detection was further determined using a fluorescent signal intensity measurement method via a portable reader, in combination with fluorescence imaging analysis. The degree to which the fluorescence signal response is detected is proportional to the amount of the target virus protein present in the system, reflected by the accumulation of the formed particle-antibody conjugates within the test system. Under optimized conditions, the system is capable of detecting the influenza B virus protein at a level of 0.55 µg per test within 30 min, using small sample volumes as low as 100 µL (R2 = 0.9544). In addition to its simplicity, further application of the system in detecting the influenza B virus protein was demonstrated using the viral transport media as specimen matrices. It was also shown that the system can perform the detection without cross-reactivity to other closely related respiratory viruses.

Epitope-imprinted polydopamine electrochemical sensor for ovalbumin detection.

A novel, sensitive and selective electrochemical sensor based on epitope-imprinted polydopamine (PDA) was developed for ovalbumin (OVA) detection. Molecularly imprinted polydopamine was synthesized on an AuNP-coated screen-printed carbon electrode (SPCE) via electropolymerization in the presence of OVA IgE-binding epitope as the template. Key process parameters including template concentration, electropolymerization cycle, pH, time required for template removal and rebinding were optimized. Electrochemical detection of OVA was performed by differential pulse voltammetry (DPV) in 5 mM K3Fe(CN)6 and 0.1 M KCl as the supporting electrolyte. Under optimized conditions, the sensor demonstrated excellent sensitivity toward OVA with linear range from 23.25 to 232.50 nM (1 to 10 ppm), limit of detection (LOD) of 10.76 nM (0.46 ppm), and limit of quantification (LOQ) of 35.87 nM (1.54 ppm). The sensor also exhibited good selectivity against other proteins such as human serum albumin (HSA), bovine serum albumin (BSA), and lysozyme (LYZ). OVA in wine samples was detected with RSD of 5.63-10.82%, and recovery percentage of 104.74-105.96%. The developed method can be easily adapted to detect other allergic proteins in the food supply chain.

Aptamer-functionalised magnetic particles for highly selective detection of urinary albumin in clinical samples of diabetic nephropathy and other kidney tract disease.

We report a new highly selective detection platform for human albumin (HA) in urine based on aptamer-functionalised magnetic particles. Magnetic separation and re-dispersion was utilised to expose the HA-bound particles to a methylene blue solution. A second magnetic collection step was then used to allow the methylene blue supernatant to be reduced at an unmodified screen-printed electrode. Since methylene blue adsorbs to HA, the reduction current fell in proportion to HA concentration. There was no interference from compounds such as dopamine, epinephrine, vanillylmandelic acid, normetanephrine, metanephrine and creatinine in artificial urine at the concentrations at which they would be expected to appear. A calibration equation was derived to allow for the effect of pH on the response. This enabled measurement to be made directly in clinical urine samples of varying pH. After optimisation of experimental parameters, the total assay time was 40 min and the limit of detection was between 0.93 and 1.16 µg mL-1, depending on the pH used. HA could be detected up to 400 µg mL-1, covering the range from normoalbuminuria to macroalbuminuria. Analysis of urine samples of patients, with diabatic nephropathy, type I & II diabetes mellitus and chronic kidney disease, from a local hospital showed good agreement with the standard urinary human albumin detection method.

A highly sensitive electrochemical microRNA-21 biosensor based on intercalating methylene blue signal amplification and a highly dispersed gold nanoparticles/graphene/polypyrrole composite.

Numerous clinical studies suggest that microRNAs (miRNAs) are indicative biomolecules for the early diagnosis of cancer. This work aims to develop a cost-effective and label-free electrochemical biosensor to detect miRNA-21, a biomarker of breast cancer. An electrochemical sensor is fabricated using a nanocomposite, consisting of graphene (GP), polypyrrole (PPY) and gold nanoparticles (AuNPs), modified onto a screen-printed carbon electrode (SPCE) to improve electron transfer properties and increase the degree of methylene blue (MB) intercalation for signal amplification. The GP/PPY-modified electrode offers good electrochemical reactivity and high dispersibility of AuNPs, resulting in excellent sensor performance. Peak current of the MB redox process, which is proportional to miRNA-21 concentration on the electrode surface, is monitored by differential pulse voltammetry (DPV). Under optimal conditions, this sensor is operated by monitoring the MB signal response due to the amount of hybridization products between miRNA-21 target molecules and DNA-21 probes immobilized on the electrode. The proposed biosensor reveals a linear range from 1.0 fM to 1.0 nM with a low detection limit of 0.020 fM. In addition, the miRNA-21 biosensor provides good selectivity, high stability, and satisfactory reproducibility, which shows promising potential in clinical research and diagnostic applications.

Pre-clinically evaluated visual lateral flow platform using influenza A and B nucleoprotein as a model and its potential applications.

A visual colorimetric rapid screening system based on a lateral flow device for simultaneous detection and differentiation between influenza A and B nucleoprotein as a model was developed. Monoclonal antibodies, specific for either influenza A or B nucleoproteins, were evaluated for their reactivities and were used as targeting ligands. With the best antibody pairs selected, the system exhibited good specificity to both viruses without cross reactivity to other closely related respiratory viruses. Further semi-quantitative analysis using a strip reader revealed that the system is capable of detecting influenza A and B protein content as low as 0.04 and 1 ng per test, respectively, using a sample volume as low as 100 µL, within 10 minutes (R 2 = 0.9652 and 0.9718). With a performance comparison to the commercial tests, the system demonstrated a four-to-eight-fold higher sensitivity. Pre-clinical evaluation with 101 nasopharyngeal swabs reveals correlated results with a standard molecular approach, with 89% and 83% sensitivity towards influenza A and B viruses, and 100% specificity for both viruses.

Hyaluronic acid-coated gold nanorods enhancing BMP-2 peptide delivery for chondrogenesis.

Bone morphogenic protein-2 (BMP-2) knuckle epitope peptide has been recently discovered and known to activate chondrogenesis. However, the applications of this soluble peptide remain very limited due to rapid diffusion resulting in poor cellular uptake into target cells. We herein designed nanoparticles made from hyaluronic acid functionalized gold nanorods (GNRs) to conjugate with thiolated BMP-2 knuckle epitope peptide via a two-step reaction. Hyaluronic acid was modified to have thiol functional groups to replace the cetyl trimethylammonium bromide ligands on the surface of GNRs. The thiolated peptides were subsequently reacted with hyaluronic acid on the surface on GNRs via a maleimide-hydrazide crosslinker. The conjugation was confirmed by the change of surface charge of GNRs and the plasmon shift. A colorimetric peptide assay suggested more than 69% of the thiolated peptides were conjugated with the hyaluronic acid coated gold nanorods. Moreover, in vitro cell viability showed that BMP-2 conjugated hyaluronic acid functionalized gold nanorods (B2HGR) were cytocompatible and did not cause cytotoxicity to fibroblast cells. The B2HGRs also significantly promote cellular uptake of the BMP-2 peptides in both human mesenchymal stem cells and porcine chondrocytes due to multivalent ligand binding to the BMP receptors on the cell surface resulting in receptor-mediated endocytosis. The enhanced cellular uptake was clearly observed under a confocal microscope resulting in the significant activation of type II collagen gene expression and glucosaminoglycan secretion in those cells. Furthermore, our delivery system is a proof-of-concept of using scaffolds in combination with nanodelivery platform to enhance cartilaginous repair. The peptide loading capacity and the release is not limited by the scaffolds. Therefore, our delivery platform has potential applications for cartilage regeneration in a preclinical and clinical setting in the future.

Nanotechnology in therapeutics: a focus on nanoparticles as a drug delivery system.

Continuing improvement in the pharmacological and therapeutic properties of drugs is driving the revolution in novel drug delivery systems. In fact, a wide spectrum of therapeutic nanocarriers has been extensively investigated to address this emerging need. Accordingly, this article will review recent developments in the use of nanoparticles as drug delivery systems to treat a wide variety of diseases. Finally, we will introduce challenges and future nanotechnology strategies to overcome limitations in this field.

Pattern recognition of cancer cells using aptamer-conjugated magnetic nanoparticles.

Biocompatible magnetic nanosensors based on reversible self-assembly of dispersed magnetic nanoparticles into stable nanoassemblies have been used as effective magnetic relaxation switches (MRSw) for the detection of molecular interactions. We report, for the first time, the design of MRSw based on aptamer-conjugated magnetic nanoparticles (ACMNPs). The ACMNPs capitalize on the ability of aptamers to specifically bind target cancer cells, as well as the large surface area of MNPs to accommodate multiple aptamer binding events. The ACMNPs can detect as few as 10 cancer cells in 250 µL of sample. The ACMNPs' specificity and sensitivity are also demonstrated by detection in cell mixtures and complex biological media, including fetal bovine serum, human plasma, and whole blood. Furthermore, by using an array of ACMNPs, various cell types can be differentiated through pattern recognition, thus creating a cellular molecular profile that will allow clinicians to accurately identify cancer cells at the molecular and single-cell level.

Smart multifunctional nanostructure for targeted cancer chemotherapy and magnetic resonance imaging.

Targeted chemotherapy and magnetic resonance imaging of cancer cells in vitro has been achieved using a smart multifunctional nanostructure (SMN) constructed from a porous hollow magnetite nanoparticle (PHMNP), a heterobifunctional PEG ligand, and an aptamer. The PHMNPs were prepared through a three-step reaction and loaded with the anticancer drug doxorubicin while being functionalized with PEG ligands. Targeting aptamers were then introduced by reaction with the PEG ligands. The pores of the PHMNPs are stable at physiological pH, but they are subject to acid etching. Specific binding and uptake of the SMN to the target cancer cells induced by aptamers was observed. In addition, multiple aptamers on the surface of one single SMN led to enhanced binding and uptake to target cancer cells due to the multivalent effect. Upon reaching the lysosomes of target cancer cells through receptor-mediated endocytosis, the relatively low lysosomal pH level resulted in corrosion of the PHMNP pores, facilitating the release of doxorubicin to kill the target cancer cells. In addition, the potential of using SMN for magnetic resonance imaging was also investigated.

Detection of lysozyme magnetic relaxation switches based on aptamer-functionalized superparamagnetic nanoparticles.

Magnetic relaxation switch (MRSw) detection is based on aggregate formation or dissociation when magnetic nanoparticles (MNPs) bind to target molecules. In the aggregated state, the dephasing rate of nearby proton spins is higher than in the dispersed state, resulting in a decrease in the spin-spin relaxation time, T(2). In this work, an MRSw-based nanosensor for lysozyme (Lys) protein detection was achieved using iron oxide nanoparticles conjugated with either Lys aptamer or linker DNA, which can hybridize with the extended part of the aptamer to form clusters. Upon the addition of Lys, the aptamers bind with their targets, leading to disassembly of clusters and an increase in T(2). A detection limit in the nanomolar range was achieved for Lys detection in both buffer and human serum. The determination of Lys level in different types of cancer cell lysates was also performed to demonstrate detection in real clinical samples.