Multimodal Detection of a Small Molecule Target Using Stimuli-Responsive Liposome Triggered by Aptamer-Enzyme Conjugate

Recent advances in nucleic acid-functionalized metallic nanoparticles

Nucleic acid-functionalized metallic nanoparticles (N-MNPs) precisely integrate the advantageous characteristics of nucleic acids and metallic nanomaterials, offering various abilities such as resistance to enzymatic degradation, penetration of physiological barriers, controllable mobility, biomolecular recognition, programmable self-assembly, and dynamic structure-function transformation. These properties demonstrate significant potential in the field of biomedical diagnostics and therapeutics. In this review, we examine recent advancements in the construction and theranostic applications of N-MNPs. We briefly summarize the methodologies employed in the conjugation of nucleic acids with metallic nanoparticles and the formation of their superstructural assemblies. We highlight recent representative applications of N-MNPs in biomolecular diagnosis, imaging, and smart delivery of theranostic agents. We also discuss challenges currently faced in this field and provide an outlook on future development directions and application prospects.

Molecular engineering of functional DNA molecules toward point-of-care diagnostic devices

The pursuit of rapid, sensitive, and specific diagnostic methodologies is imperative across diverse applications, including the detection of pathogens and disease biomarkers, food safety testing and environmental monitoring. Point-of-care testing (POCT) is characterized by its portability, ease of use, rapidity, and affordability, emerging as an attractive alternative for traditional diagnostics. Over recent years, the incorporation of functional DNA (fDNA) into POC diagnostic devices has emerged as a groundbreaking advancement, significantly enhancing sensitivity, specificity, and user-friendliness. In this review, we explore the innovative applications of fDNA in POC devices, highlighting its potential to revolutionize diagnostics by providing rapid, portable, and precise solutions. We discuss the unique advantages of fDNA, including its stability in complex biological matrices and its ability to recognize a wide range of targets. Furthermore, we explore the potential synergy between fDNA and cutting-edge technologies, such as nanotechnology and artificial intelligence (AI), to forge a path toward more personalized and accessible healthcare solutions. Despite significant progress, challenges remain in translating these innovations from the bench to the clinic. This review aims to provide a comprehensive overview of the current status of fDNA-based POCT devices and future directions for their development, emphasizing their critical role in meeting the global demand for accessible, efficient, and precise diagnostic solutions.

A novel triple signal amplification platform of peroxide test strip for sensitive detection of adenosine triphosphate

Peroxide test strip (PTS) has been widely used for the point-of-care testing (POCT), but its poor sensitivity is a big obstacle for analyzing trace target. Herein, a triple signal amplifying platform integrating the liposome enrichment, the hybridization chain reaction (HCR) circuit, and the image analysis method was constructed to enhance the visual readout of PTS for the sensitive detection of adenosine triphosphate (ATP), an important biomarker of food spoilage. In the presence of ATP, the HCR amplifier was firstly initiated on the surface of magnetic beads (MBs), inducing a large number of glucose oxidase (GOD) imbedded liposomes to be attached. After the magnetic separation, the linked liposomes were destroyed and the enriched GOD was released to react with glucose to produce H2O2, which can enhance the color change of PTS. Finally, an image analysis method was developed to further amplify the colorimetric difference of human visual perception of PTS readout. This triple signal amplification strategy was used to detect ATP in the linear range from 50 to 250 nmol/L, and the limit of detection (LOD, 3σ/k) was 0.65 nmol/L. Finally, this method has been successfully applied for accurate and sensitive detection of ATP in watermelon juice, showing its great potential for quick determining whether food is spoiled.

Specific surface modification of liposomes for gut targeting of food bioactive agents

Liposomes have become a research hotspot in recent years as food delivery systems with attractive properties, including the bilayer structure assembled like the cell membrane, reducing the side-effect and improving environmental stability of cargos, controlling release, extending duration of functional ingredients, and high biodegradable and biocompatible abilities in the body. However, the conventional liposomes lack stability during storage and are weak in targeted absorption in the gastrointestinal track. At present, surface modification has been approved to be an effective platform to shield these barricades and help liposomes deliver the agents safely and effectively to the ideal site. In this review, the gastrointestinal stability of conventional liposomes, cargo release models from liposomes, and the biological fate of the core materials after release were emphasized. Then, the strategies in both physical and chemical perspectives to improve the stability and utilization of liposomes in the gastrointestinal tract, and the emerging approaches for improving gut targeting by specifically modified liposomes and the intestinal receptors relative to liposomes/cargos absorption were highlighted. Last but not the least, the safety, challenges, and opportunities for the improvement of liposomal bioavailability were also discussed to inspire new applications of liposomes as oral carriers.

Overcoming Major Barriers to Developing Successful Sensors for Practical Applications Using Functional Nucleic Acids

For many years, numerous efforts have been focused on the development of sensitive, selective, and practical sensors for environmental monitoring, food safety, and medical diagnostic applications. However, the transition from innovative research to commercial success is relatively sparse. In this review, we identify four scientific barriers and one technical barrier to developing successful sensors for practical applications, including the lack of general methods to (a) generate receptors for a wide range of targets, (b) improve sensor selectivity to overcome interferences, (c) transduce the selective binding to different optical, electrochemical, and other signals, and (d) tune dynamic range to match thresholds of detection required for different targets; and the costly development of a new device. We then summarize solutions to overcome these barriers using sensors based on functional nucleic acids that include DNAzymes, aptamers, and aptazymes and how these sensors are coupled to widely available measurement devices to expand their capabilities and lower the barrier for their practical applications in the field and point-of-care settings.

Engineering DNA/Fe-N-C single-atom nanozymes interface for colorimetric biosensing of cancer cells

Single atom nanozymes (SAzymes) represent the state-of-the-art technology in nanomaterial-based catalysis, which have attracted attentions in catalysis, cancer treatment, disinfection and biosensing fields. However, numerous SAzymes suffered from low aqueous dispersion and without recognition capacity, which impeded their applications in bioanalysis. Herein, we engineered DNA onto SAzymes to obtain the DNA/SAzymes conjugates, which significantly improved the aqueous dispersion and recognition ability of SAzymes. We synthesized iron SAzymes (Fe-N-C SAzymes) as the catalytic nanomaterials, and investigated the interactions between Fe-N-C SAzymes and DNA. We compared A₁₅, T₁₅ and C₁₅ adsorption of Fe-N-C SAzymes in HEPES containing 2 mM MgCl₂. We found that 50 μg mL^-1 Fe-N-C SAzymes produced nearly 100% A₁₅ adsorption, 90% T₁₅ adsorption and only 69% C₁₅ adsorption, indicating that adenine and thymine had higher adsorption affinity on Fe-N-C SAzymes. More importantly, DNA modification did not affect the peroxidase-like activity of Fe-N-C SAzymes and the bioactivity of the adsorbed DNA. Taking the advantage of the diblock DNA with one DNA sequence (adenine) binding to Fe-N-C SAzymes and the other DNA sequence (i.e., aptamer) binding to cancer cells, we designed Apt/Fe-N-C SAzymes for colorimetric detection of cancer cells, which offered new insights for the use of SAzymes in biomedicine.

Facile Method for Specifically Sensing Sphingomyelinase in Cells and Human Urine Based on a Ratiometric Fluorescent Nanoliposome Probe

Sphingomyelinase (SMase) is closely related to diseases like Niemann-Pick disease and atherosclerosis, and the development of a simple method for the assay of SMase activity is very useful to screen new potential inhibitors or stimulators of SMase or biomarkers of disease. Fluorophore-encapsulated nanoliposomes (FENs) are emerging as a new fluorescent probe for sensing the enzymatic activity. In this work, two fluorochromes (cy7 and IR780) were encapsulated into the liposome of sphingomyelin, and therefore, a sphingomyelin-based ratiometric FEN probe for the SMase activity assay was constructed. The probe shows high selectivity and sensitivity to acid SMase with a detection limit of 4.8 × 10^-4 U/mL. Sphingomyelin is the natural substrate of SMase; therefore, the probe has native ability for all kinds of SMase activity assays. Moreover, the probe has been successfully applied to the analysis of acid SMase activity in cells and urine samples. As far as we know, this is the first example of a nanoliposome fluorescence method for assaying acid SMase, and the method is biocompatible and much simpler than the existing ones, which might provide a new strategy for developing new methods for other important esterases.

Photoluminescent Nanoparticles for Chemical and Biological Analysis and Imaging

Research related to the development and application of luminescent nanoparticles (LNPs) for chemical and biological analysis and imaging is flourishing. Novel materials and new applications continue to be reported after two decades of research. This review provides a comprehensive and heuristic overview of this field. It is targeted to both newcomers and experts who are interested in a critical assessment of LNP materials, their properties, strengths and weaknesses, and prospective applications. Numerous LNP materials are cataloged by fundamental descriptions of their chemical identities and physical morphology, quantitative photoluminescence (PL) properties, PL mechanisms, and surface chemistry. These materials include various semiconductor quantum dots, carbon nanotubes, graphene derivatives, carbon dots, nanodiamonds, luminescent metal nanoclusters, lanthanide-doped upconversion nanoparticles and downshifting nanoparticles, triplet-triplet annihilation nanoparticles, persistent-luminescence nanoparticles, conjugated polymer nanoparticles and semiconducting polymer dots, multi-nanoparticle assemblies, and doped and labeled nanoparticles, including but not limited to those based on polymers and silica. As an exercise in the critical assessment of LNP properties, these materials are ranked by several application-related functional criteria. Additional sections highlight recent examples of advances in chemical and biological analysis, point-of-care diagnostics, and cellular, tissue, and in vivo imaging and theranostics. These examples are drawn from the recent literature and organized by both LNP material and the particular properties that are leveraged to an advantage. Finally, a perspective on what comes next for the field is offered.

A DNA-mediated crosslinking strategy to enhance cellular delivery and sensor performance of protein spherical nucleic acids

Intracellular delivery of enzymes is essential for protein-based diagnostic and therapeutic applications. Protein-spherical nucleic acids (ProSNAs) defined by protein core and dense shell of oligonucleotides have been demonstrated as a promising vehicle-free enzyme delivery platform. In this work, we reported a crosslinking strategy to vastly improve both delivery efficiency and intracellular sensor performance of ProSNA. By assembling individual ProSNA with lactate oxidase (LOX) core into a nanoscale particle, termed as crosslinked SNA (X-SNA), the enzyme delivery efficiency increased up to 5-6 times higher. The LOX X-SNA was later demonstrated as a ratiometric probe for quantitative detection of lactate in living cells. More importantly, X-SNA probe showed significantly improved sensor performance with signal-to-noise ratio 4 times as high as ProSNA when detecting intracellular lactate.

Differential Photoelectrochemical Biosensing Using DNA Nanospacers to Modulate Electron Transfer between Metal and Semiconductor Nanoparticles

As dynamic biorecognition agents such as functional nucleic acids become widely used in biosensing, there is a need for ultrasensitive signal transduction strategies, beyond fluorescence, that are robust and stable for operation in heterogeneous biological samples. Photoelectrochemical readout offers a pathway toward this goal as it offers the simplicity and scalability of electrochemical readout, in addition to compatibility with a broad range of nanomaterials used as labels for signal transduction. Here, a differential photoelectrochemical biosensing approach is reported, in which DNA nanospacers are used to program the response of two sensing channels. The differences in the motional dynamics of DNA probes immobilized on different channels are used to control the interaction between Au and TiO₂ nanoparticles positioned at the two ends of the DNA nanospacer to achieve differential signal generation. Depending on the composition of the DNA constructs (fraction of the DNA sequence i.e., double-stranded), the channels can be programmed to produce a signal-on or a signal-off response. Incident photon-to-current conversion efficiency, UV-vis spectroscopy, and flat-band potential measurement indicate that direct transfer of electrons between metallic and semiconductive nanoparticles is responsible for the signal-on response, and incident light absorption and steric hindrance are responsible for the signal-off response. The differential photoelectrochemical signal readout developed here increases the device sensitivity by up to three times compared to a single channel design and demonstrates a limit of detection of 800 aM.

Liposomes with pH responsive 'on and off' switches for targeted and intracellular delivery of antibiotics

pH responsive drug delivery systems are one of the new strategies to address the spread of bacterial resistance to currently used antibiotics. The aim of this study was to formulate liposomes with 'On' and 'Off'' pH responsive switches for infection site targeting. The vancomycin (VCM) loaded liposomes had sizes below 100 nm, at pH 7.4. The QL-liposomes had a negative zeta potential at pH 7.4 that switched to a positive charge at acidic pH. VCM release from the liposome was quicker at pH 6 than pH 7.4. The OA-QL-liposome showed 4-fold lower MIC at pH 7.4 and 8- and 16-fold lower at pH 6.0 against both MSSA and MRSA compared to the bare drug. OA-QL liposome had a 1266.67- and 704.33-fold reduction in the intracellular infection for TPH-1 macrophage and HEK293 cells respectively. In vivo studies showed that the amount of MRSA recovered from mice treated with formulations was 189.67 and 6.33-fold lower than the untreated and bare VCM treated mice respectively. MD simulation of the QL lipid with the phosphatidylcholine membrane (POPC) showed spontaneous binding of the lipid to the bilayer membrane both electrostatic and Van der Waals interactions contributed to the binding. These studies demonstrated that the 'On' and 'Off' pH responsive liposomes enhanced the activity targeted and intracellular delivery VCM.

Functional DNA Molecules Enable Selective and Stimuli-Responsive Nanoparticles for Biomedical Applications

Nanoparticles (NPs) have enormous potential to improve disease diagnosis and treatment due to their intrinsic electronic, optical, magnetic, mechanical, and physiological properties. To realize their full potential for nanomedicine, NPs must be biocompatible and targetable toward specific biomolecules to ensure selective sensing, imaging, and drug delivery in complex environments such as living cells, tissues, animals, and human bodies. In this Account, we summarize our efforts to impart specific biocompatibility and biorecognition functionality to NPs by developing strategies to integrate inorganic and organic NPs with functional DNA (fDNA), including aptamers, DNAzymes, and aptazymes to create fDNA-NPs. These hybrid NPs take advantage of fDNA's ability to either bind targets or catalyze reactions in the presence of targets selectively and utilize their unique physicochemical properties including small size, low immunogenicity, and ease of synthesis and chemical modification in comparison with other molecules such as antibodies. By integrating inorganic NPs such as gold NPs, quantum dots, and iron oxide nanoparticles with fDNA, we designed stimuli-responsive fDNA-NPs that exhibit target induced assembly and disassembly of NPs, resulting in a variety of colorimetric, fluorescent, and magnetic resonance imaging (MRI)-based sensors for diagnostic of a broad range of analytes. To impart both biocompatibility and selectivity on inorganic NPs for targeted bioimaging, we have demonstrated DNA-mediated surface functionalization, shape-controlled synthesis, and coordinative assembly of such NPs as specific bioprobes. A highlight is provided on the construction of fDNA-based nanoprobes with light-activatable sensing and imaging functions, which provides precise control of recognition properties of fDNA with high spatiotemporal resolution. To explore the potential of organic NPs for biosensing applications, we have developed an enzyme-responsive fDNA-liposome as a universal sensing platform compatible with diverse biological targets as well as different detection methods including fluorescence, MRI, or temperature, making possible point-of-care diagnostics. To expand the application regime of organic NPs, we collaborated with the Zimmerman group to prepare single-chain block copolymer-based NPs and incorporated it with a variety of functions, including monovalent DNA for assembly, tunable surface chemistry for cellular imaging, and coordinative Cu(II) sites for catalyzing intracellular click reactions, demonstrating the potential of using organic NPs to create promising fDNA-NP systems with programmable functionalities. Furthermore, we survey our recent endeavor in integration of cell-specific aptamers with different NPs for targeted drug delivery, showing that introducing stimuli-responsive properties into NPs that target tumor microenvironments would enable safer and more effective therapy for cancers. Finally, current challenges and future perspectives in fDNA-mediated engineering of NPs for biomedical applications are discussed.

Electrochemical thrombin aptasensor based on using magnetic nanoparticles and porous carbon prepared by carbonization of a zinc(II)-2-methylimidazole metal-organic framework

A homogeneous electrochemical aptasensor was obtained by modifying a glassy carbon electrode (GCE) with a porous carbon nanomaterial (Z-1000, about 70 nm, deteced by transmission electron microscopic) that was obtained by carbonization of a zinc(II)-2-methylimidazole metal-organic framework. Z-1000 possesses a large specific surface and outstanding electrochemical properties. A thrombin-binding aptamer (CP) was immobilized on the magnetite nanoparticles MNPs by the condensation reaction and further combined with reporter probe (RP) that is functionalized with electroactive methylene blue (MB). In the presence of thrombin, the CP was specifically recognized with it to form the CP/MNP/Thb complex, and the RP was dissociated from MNPs. The released RP was captured by the modified GCE through π-stacking interaction between nucleobases and carbon nanostructure. The electrical signal generated by MB can be monitored by differential pulse voltammetry (DPV). Under the optimized conditions, the DPV peak current at around -0.28 V (vs. SCE) increases with thrombin concentration. The sensor has a detection limit of 0.8 fM of thrombin and a linear range that extends from 10 fM to 100 nM. It was successfully applied to the analysis of spiked serum. The recoveries are 98.1-99.4% and RSDs are 3.9%-4.0%. Conceivably, this aptasensor scheme can be easily extended to other proteins and gives inspiration to manufacture sensitive aptasensor. Graphical abstract A homogeneous electrochemical aptasensor is obtained by modifying a glassy carbon electrode with the MOF-derived porous carbon. The sensor has a detection limit of 0.8 fM and a wide linear range from 10 fM to 100 nM for thrombin detection.

Photothermal Soft Nanoballs Developed by Loading Plasmonic Cu2- xSe Nanocrystals into Liposomes for Photothermal Immunoassay of Aflatoxin B1

Photothermal effects (PTEs) have been greatly concerned with the fast development of new photothermal nanomaterials. Herein we propose a photothermal immunoassay (PTIA) by taking mycotoxins (AFB1) as an example based on the PTEs of plasmonic Cu2- xSe nanocrystals (NCs). By loading plasmonic Cu2- xSe NCs into liposomes to form photothermal soft nanoballs (ptSNBs), on which aptamer of AFB1 previously assembled, a sandwich structure of AFB1 could be formed with the aptamer on ptSNBs and capture antibody. The heat released from the ptSNBs under NIR irradiation, owing to the plasmonic photothermal light-to-heat conversion through photon-electron-phonon coupling, makes the temperature of substrate solution increased, and the increased temperature has a linear relationship with the AFB1 content. Owing to the large amounts of plasmonic Cu2- xSe NCs in the ptSNBs, the PTEs get amplified, making AFB1 higher than 1 ng/mL detectable in food even if with a rough homemade immunothermometer. The proposal of PTIA opens a new field of immunoassay including developing photothermal nanostructures, new thermometers, PTIA theory, and so on.

Molecular Engineering of Functional Nucleic Acid Nanomaterials toward In Vivo Applications

Recent advances in nanotechnology and engineering have generated many nanomaterials with unique physical and chemical properties. Over the past decade, numerous nanomaterials are introduced into many research areas, such as sensors for environmental monitoring, food safety, point-of-care diagnostics, and as transducers for solar energy transfer. Meanwhile, functional nucleic acids (FNAs), including nucleic acid enzymes, aptamers, and aptazymes, have attracted major attention from the biomedical community due to their unique target recognition and catalytic properties. Benefiting from the recent progress of molecular engineering strategies, the physicochemical properties of nanomaterials are endowed by the target recognition and catalytic activity of FNAs in the presence of a target analyte, resulting in numerous smart nanoprobes for diverse applications including intracellular imaging, drug delivery, in vivo imaging, and tumor therapy. This progress report focuses on the recent advances in designing and engineering FNA-based nanomaterials, highlighting the functional outcomes toward in vivo applications. The challenges and opportunities for the future translation of FNA-based nanomaterials into clinical applications are also discussed.

Aptamer-Structure Switch Coupled with Horseradish Peroxidase Labeling on a Microplate for the Sensitive Detection of Small Molecules

Detection of small molecules with good sensitivity, high throughput, simplicity, and generality using aptamers is desired but still remains challenging. We described an aptamer-structure-switch assay coupled with horseradish peroxidase (HRP) labeling on microplates for sensitive absorbance and chemiluminescence detection of small molecules. This assay relies on competition for affinity binding to a limited HRP-labeled aptamer between small-molecule targets and immobilized short DNA strands complementary to the aptamer (cDNA) on a microplate. In the absence of targets, the HRP-labeled aptamer hybridizes with the cDNA on the microplate, and HRP catalyzes substrate into product, generating absorbance or chemiluminescence signals. The binding of small-molecule targets to aptamers causes displacement of HRP-labeled aptamers from the cDNA and signal decrease. In chemiluminescence-analysis mode, the assay achieved detection of aflatoxin B1 (AFB1), ochratoxin A (OTA), and adenosine triphosphate (ATP) with detection limits of 10 pM, 20 pM, and 20 nM, respectively. This assay does not require enzyme-labeled small molecules or the conjugation of small molecules on solid phase. HRP, as an enzyme label, here allows for easily obtainable and highly active signal amplification. This microplate assay is rapid and promising for high-throughput analysis. It shows potential for wide applications in the detection of small molecules.

Recent development in biodegradable nanovehicle delivery system-assisted immunotherapy

A schematic illustration of BNDS biodegradation and release antigen delivery for assisting immunotherapy.

A target-responsive liposome activated by catalytic hairpin assembly enables highly sensitive detection of tuberculosis-related cytokine

Here, we propose a new fluorescence method to detect tuberculosis-related cytokine by using a target-responsive liposome activated by catalytic hairpin assembly. The method combines a DNA self-assembly based amplification process with a liposome-based signal amplification process, therefore offering a very high sensitivity.

Next-Generation DNA-Functionalized Quantum Dots as Biological Sensors

DNA-functionalized quantum dots (DNA-QDs) have found considerable application in biosensing and bioimaging. Different from the first generation (I-G) DNA-QDs prepared via conventional bioconjugation chemistry, the second generation (II-G) DNA-QDs prepared via one-step DNA-templated QD synthesis features a defined number of DNA valencies (usually monovalency), which is preferable for controlled assembly and biological targeting. In this review, we summarize recent progress in designing QD probes based on II-G DNA-QDs for advanced sensing and imaging applications. It opens up new avenues for highly sensitive and intelligent sensing of a range of disease-relevant biomolecules in vitro and in living cells.

Controlled drug delivery vehicles for cancer treatment and their performance

Although conventional chemotherapy has been successful to some extent, the main drawbacks of chemotherapy are its poor bioavailability, high-dose requirements, adverse side effects, low therapeutic indices, development of multiple drug resistance, and non-specific targeting. The main aim in the development of drug delivery vehicles is to successfully address these delivery-related problems and carry drugs to the desired sites of therapeutic action while reducing adverse side effects. In this review, we will discuss the different types of materials used as delivery vehicles for chemotherapeutic agents and their structural characteristics that improve the therapeutic efficacy of their drugs and will describe recent scientific advances in the area of chemotherapy, emphasizing challenges in cancer treatments.

Improving the delivery of cancer therapies to tumor sites is crucial to reduce unwanted side effects and patient mortality rates. Pralay Maiti and colleagues at the Indian Institute of Technology in Varanasi, India, review the latest developments in drug delivery vehicles and treatment approaches designed to enhance the effectiveness of current cancer therapies. New nanoparticle-based carriers, hydrogels and hybrid materials that offer controlled and sustained drug release are showing great promise in animal models. Furthermore, materials that respond to stimuli such as heat, light, magnetic or electric fields are also being tested to aid target-specific drug delivery and, thus, avoid damage to healthy tissues. Although there are some challenges in translating these findings to the clinic, there is no doubt that technological advances are shaping better and safer treatment options.

Translating molecular detections into a simple temperature test using a target-responsive smart thermometer

While it has been well recognized that affordable and pocket-size devices play a major role in environmental monitoring, food safety and medical diagnostics, it often takes a tremendous amount of resources to develop such devices. Devices that have been developed are often dedicated devices that can detect only one or a few targets. To overcome these limitations, we herein report a novel target-responsive smart thermometer for translating molecular detection into a temperature test. The sensor system consists of a functional DNA-phospholipase A₂ (PLA₂) enzyme conjugate, a liposome-encapsulated NIR dye, and a thermometer interfaced with a NIR-laser device. The sensing principle is based on the target-induced release of PLA₂ from the DNA-enzyme conjugate, which catalyzes the hydrolysis of liposome to release the NIR dye inside the liposome. Upon NIR-laser irradiation, the released dye can convert excitation energy into heat, producing a temperature increase in solution, which is detectable using a thermometer. Considering the low cost and facile incorporation of the system with suitable functional DNAs to recognize many targets, the system demonstrated here makes the thermometer an affordable and pocket-size meter for the detection and quantification of a wide range of targets.

Fluorescent Immunoassay for the Detection of Pathogenic Bacteria at the Single-Cell Level Using Carbon Dots-Encapsulated Breakable Organosilica Nanocapsule as Labels

Herein, carbon dots (CDs)-encapsulated breakable organosilica nanocapsules (BONs) were facilely prepared and used as advanced fluorescent labels for ultrasensitive detection of Staphylococcus aureus. The CDs were entrapped in organosilica shells by cohydrolyzation of tetraethyl orthosilicate and bis[3-(triethoxysilyl)propyl]disulfide to form core-shell CDs@BONs, where hundreds of CDs were encapsulated in each nanocapsule. Immunofluorescent nanocapsules, i.e., anti-S. aureus antibody-conjugated CDs@BONs, were prepared to specifically recognize S. aureus. Before fluorescent detection, CDs were released from the BONs by simple NaBH₄ reduction. The fluorescent signals were amplified by 2 orders of magnitude because of hundreds of CDs encapsulated in each nanocapsule, compared with a conventional immunoassay using CDs as fluorescent labels. A linear range was obtained at the S. aureus concentration from 1 to 200 CFU mL^-1. CDs@BONs are also expected to expand to other systems and allow the detection of ultralow concentrations of targets.

Phospholipase A2-Induced Degradation and Release from Lipid-Containing Polymersomes

Hybrid vesicles, comprising blends of amphiphilic block copolymers and phospholipids, have attracted significant attention recently because of their unique combination of chemical and physical properties. We report a method to make unilamellar hybrid vesicles with diameters of 100 nm by mixing polybutadiene-block-poly(ethylene oxide) and phosphocholine lipids using a combination of solvent inversion and sonication. We show that homogeneous hybrid vesicles are formed when one component is a minor fraction. At compositions with balanced mass fractions, separate populations of similarly sized pure liposomes and hybrid vesicles are indicated. We investigate the release kinetics of calcein encapsulated in the lumen as hybrid large and giant unilamellar vesicles (LUVs and GUVs) of different compositions are exposed to phospholipase A₂ (PLA₂). PLA₂ hydrolyzes lipids, which leads to dissolution of lipid domains and provides a trigger for the release of calcein as pores are formed. We demonstrate that depending on the polymer mole fraction, block copolymers can either protect or boost the rate of lipid degradation and thereby the release rate from nanoscale hybrid vesicles. Strong indications of lipid phase separation into nanoscale domains in LUVs are observed. Most importantly, hybrid GUV with lipids in the fluid phase release calcein slowly as lipids in the liquid-disordered phase do not phase-separate, but they show the fastest release of all blends as LUVs. This indicates phase separation on the nanoscale in contrast to on the microscale, but it also indicates retained high mobility of lipids between the nanoscale domains, which is absent for lipids in the gel phase. Our results demonstrate several ways in which nanoscale hybrid vesicles can and should be optimized for PLA₂-triggered release of water-soluble compounds.

A ratiometric strategy -based electrochemical sensing interface for the sensitive and reliable detection of imidacloprid

A ratiometric electrochemical sensor was developed for selective and sensitive detection of imidacloprid. Modified poly(thionine) provided a built-in correction to endow the sensor with good accuracy and stability.

Stimuli-responsive liposomes for drug delivery

The ultimate goal of drug delivery is to increase the bioavailability and reduce the toxic side effects of the active pharmaceutical ingredient (API) by releasing them at a specific site of action. In the case of antitumor therapy, association of the therapeutic agent with a carrier system can minimize damage to healthy, nontarget tissues, while limit systemic release and promoting long circulation to enhance uptake at the cancerous site due to the enhanced permeation and retention effect (EPR). Stimuli-responsive systems have become a promising way to deliver and release payloads in a site-selective manner. Potential carrier systems have been derived from a wide variety of materials, including inorganic nanoparticles, lipids, and polymers that have been imbued with stimuli-sensitive properties to accomplish triggered release based on an environmental cue. The unique features in the tumor microenvironment can serve as an endogenous stimulus (pH, redox potential, or unique enzymatic activity) or the locus of an applied external stimulus (heat or light) to trigger the controlled release of API. In liposomal carrier systems triggered release is generally based on the principle of membrane destabilization from local defects within bilayer membranes to effect release of liposome-entrapped drugs. This review focuses on the literature appearing between November 2008-February 2016 that reports new developments in stimuli-sensitive liposomal drug delivery strategies using pH change, enzyme transformation, redox reactions, and photochemical mechanisms of activation. WIREs Nanomed Nanobiotechnol 2017, 9:e1450. doi: 10.1002/wnan.1450 For further resources related to this article, please visit the WIREs website.

Advances in the development of aptamer drug conjugates for targeted drug delivery

A key goal of modern medicine is target-specific therapeutic intervention. However, most drugs lack selectivity, resulting in 'off-target' side effects. To address the requirements of 'targeted therapy,' aptamers, which are artificial oligonucleotides, have been used as novel targeting ligands to construct aptamer drug conjugates (ApDC) that can specifically bind to a broad spectrum of targets, including diseased cells. Accordingly, the application of aptamers in targeted drug delivery has attracted broad interest due to their impressive selectivity and affinity, low immunogenicity, easy synthesis with high reproducibility, facile modification, and relatively rapid tissue penetration with no toxicity. Functionally, aptamers themselves can be used as macromolecular drugs, and they are also commonly used in biomarker discovery and targeted drug delivery. In this review, we will highlight the most recent advances in the development of aptamers and aptamer conjugates, and discuss their potential in targeted therapy. WIREs Nanomed Nanobiotechnol 2017, 9:e1438. doi: 10.1002/wnan.1438 For further resources related to this article, please visit the WIREs website.

Activatable probes for diagnosis and biomarker detection by MRI

Magnetic resonance imaging (MRI) is a non-invasive imaging technique with widespread use in diagnosis. Frequently, contrast in MRI is enhanced with the aid of a contrast agent, among which smart, responsive, OFF/ON or activatable probes are of particular interest. These kinds of probes elicit a response to selective stimuli, evidencing the presence of enzymes or acidic pH, for instance. In this review, we will focus on smart probes that are detectable by both ¹H and ¹⁹F MRI, frequently based on nanomaterials. We will discuss the triggering factors and the strategies employed thus far to activate each probe.

A glucose-activatable trimodal glucometer self-assembled from glucose oxidase and MnO2nanosheets for diabetes monitoring

For the first time a glucose-activatable trimodal glucometer with an exceptional enhanced enzymatic activity, self-assembled from glucose oxidase and MnO₂nanosheets for diabetes monitoringin vitro, has been presented.

Sensitive and selective detection of the p53 gene based on a triple-helix magnetic probe coupled to a fluorescent liposome hybridization assembly via rolling circle amplification

Developing a sensitive and selective sensing platform for the p53 gene and its mutation analysis is essential and may aid in early cancer screening and assessment of prognosis.

Recent Developments of Liposomes as Nanocarriers for Theranostic Applications

Liposomes are nanocarriers comprised of lipid bilayers encapsulating an aqueous core. The ability of liposomes to encapsulate a wide variety of diagnostic and therapeutic agents has led to significant interest in utilizing liposomes as nanocarriers for theranostic applications. In this review, we highlight recent progress in developing liposomes as nanocarriers for a) diagnostic applications to detect proteins, DNA, and small molecule targets using fluorescence, magnetic resonance, ultrasound, and nuclear imaging; b) therapeutic applications based on small molecule-based therapy, gene therapy and immunotherapy; and c) theranostic applications for simultaneous detection and treatment of heavy metal toxicity and cancers. In addition, we summarize recent studies towards understanding of interactions between liposomes and biological components. Finally, perspectives on future directions in advancing the field for clinical translations are also discussed.