Silver nanoparticle-oligonucleotide conjugates based on DNA with triple cyclic disulfide moieties

Optical and Chiroptical Stimuli-Responsive Chiral AgNPs@H-Leu-Poly(phenylacetylene) Nanocomposites in Water

Dynamic macroscopically chiral nanocomposites are prepared by combining silver nanoparticles (AgNPs) and dynamic helical poly(phenylacetylene)s (PPAs) bearing pendants functionalized with amino groups. These amino groups provide the nanocomposite with the ability to disperse in water along with high stability due to the interaction between the ammonium group and the AgNP. Moreover, the equilibrium between NH3+/NH2 produces a "blinking" contact between the PPA and the AgNPs, which allows total control of the dynamic helical behavior of the polymer. The use of acidic or neutral pH allows controlling the morphology of the nanocomposite, which consists of a nanosphere that has trapped inside it a single AgNP (pH = 2) or several AgNPs (pH = 7) with ca. 30 nm of diameter. These nanocomposites combine the optical and chiroptical stimuli-responsive properties of both components, AgNPs and PPAs. Thus, the controlled aggregation of the nanocomposite produced variations in the LSPR band of the AgNPs in a reversible manner. In turn, given that the chiral coating is selective to Ba2+, the presence of this metal ion caused a helical inversion of the chiral coating of the nanocomposite detected by electronic circular dichroism. Moreover, it is possible to distinguish between three metal ions in different oxidation states, such as Ce4+, Fe3+, and Hg2+, which produce different responses of the nanocomposite when oxidizing the AgNP to Ag+.

In Vivo Interactions of Nucleic Acid Nanostructures With Cells

Nucleic acid nanostructures, derived from the assembly of nucleic acid building blocks (e.g., plasmids and oligonucleotides), are important intracellular carriers of therapeutic cargoes widely utilized in preclinical nanomedicine applications, yet their clinical translation remains scarce. In the era of "translational nucleic acid nanotechnology", a deeper mechanistic understanding of the interactions of nucleic acid nanostructures with cells in vivo will guide the development of more efficacious nanomedicines. This review showcases the recent progress in dissecting the in vivo interactions of four key types of nucleic acid nanostructures (i.e., tile-based, origami, spherical nucleic acid, and nucleic acid nanogel) with cells in rodents over the past five years. Emphasis lies on the cellular-level distribution of nucleic acid nanostructures in various organs and tissues and the cellular responses induced by their cellular entry. Next, in the spirit of preclinical translation, this review features the latest interactions of nucleic acid nanostructures with cells in large animals and humans. Finally, the review offers directions for studying the interactions of nucleic acid nanostructures with cells from both materials and biology perspectives and concludes with some regulatory updates.

Smart Stimuli-Responsive Spherical Nucleic Acids: Cutting-Edge Platforms for Biosensing, Bioimaging, and Therapeutics

Spherical nucleic acids (SNAs) with exceptional colloidal stability, multiple modularity, and programmability are excellent candidates to address common molecular delivery-related issues. Based on this, the higher targeting accuracy and enhanced controllability of stimuli-responsive SNAs render them precise nanoplatforms with inestimable prospects for diverse biomedical applications. Therefore, tailored diagnosis and treatment with stimuli-responsive SNAs may be a robust strategy to break through the bottlenecks associated with traditional nanocarriers. Various stimuli-responsive SNAs are engineered through the incorporation of multifunctional modifications to meet biomedical demands with the development of nucleic acid functionalization. This review provides a comprehensive overview of prominent research in this area and recent advancements in the utilization of stimuli-responsive SNAs in biosensing, bioimaging, and therapeutics. For each aspect, SNA nanoplatforms that exhibit responsive behavior to both internal stimuli (including sequence, enzyme, redox reactions, and pH) and external stimuli (such as light and temperature) are highlighted. This review is expected to offer inspiration and guidance strategies for the rational design and development of stimuli-responsive SNAs in the field of biomedicine.

A simple and rapid colorimetric detection of Staphylococcus aureus relied on the distance-dependent optical properties of silver nanoparticles

The quick and accurate diagnosis of pathogens has appeared as a pressing issue in clinical diagnostics, environmental monitoring, and food safety. The available assays are suffering from limited capacities in simple, fast, low-cost, and on-site detection to increase prevention and proper treatment. Herein, we address these challenges by developing a simple, speedy, affordable, and ultrasensitive nanoplasmonic biosensor for colorimetric detection of cDNA from staphylococcal RNA relying on the distance-dependent optical features of silver nanostructures for the measurement of color variations and spectral shifts owing to the plasmon coupling generated by the cross-linking accumulation of AgNPs. The method described utilizes silver nanoparticles (AgNPs) immobilized with two different single-stranded oligonucleotides (ssDNA1 and ssDNA2) that specifically recognize the target DNA. Sandwich hybridization of target DNA with ssDNA1 and ssDNA2 induced color variations and spectral shifts of AgNPs, whereas test samples without the target DNA remained yellow as the initial color of colloidal silver. The designed nanoplasmonic biosensor demonstrated high specificity with the detection limit (LOD) of ∼1.8 amol target DNA (∼106 molecules per test) in the broad linear dynamic range from 0.01 to 100 nM, and LOD down to a few cells was attained for amplified bacterial nucleic acids and a linear range from 102 CFU mL-1 to 107 CFU mL-1. The sensing approach showed great potential for the timely diagnosis of pathogens in low-density samples, and it has considerable merits over traditional culture approaches and qPCR techniques.

Improving the sensing sensitivity of silver nanoparticle-based colorimetric biosensors from the point of salt

The sensing sensitivity was improved for silver nanoparticles (AgNPs)-based colorimetric biosensors by using the most suitable salt to induce AgNPs aggregation. As for the salt composed of low-affinity anion and monovalent cation, the cation-dependent charge screening effect was the driving force for AgNPs aggregation. Apart from the charge screening effect, both the bridging of multivalent cation to the surface ligand of AgNP and the interaction between anion and Ag contributed to inducing AgNPs aggregation. Considering the higher aggregation efficiency of AgNPs resulted in a narrower sensing range, salt composed of low-affinity anion and monovalent cation was recommended for AgNPs-based colorimetric analysis, which was confirmed by fourfold higher sensitivity of DNA-21 detection using NaF than NaCl. This work inspires further thinking on improving the sensing performance of metal nanomaterials-based sensors from the point of colloidal surface science.

Spherical nucleic acids-based nanoplatforms for tumor precision medicine and immunotherapy

Precise diagnosis and treatment of tumors currently still face considerable challenges due to the development of highly degreed heterogeneity in the dynamic evolution of tumors. With the rapid development of genomics, personalized diagnosis and treatment using specific genes may be a robust strategy to break through the bottleneck of traditional tumor treatment. Nevertheless, efficient in vivo gene delivery has been frequently hampered by the inherent defects of vectors and various biological barriers. Encouragingly, spherical nucleic acids (SNAs) with good modularity and programmability are excellent candidates capable of addressing traditional gene transfer-associated issues, which enables SNAs a precision nanoplatform with great potential for diverse biomedical applications. In this regard, there have been detailed reviews of SNA in drug delivery, gene regulation, and dermatology treatment. Still, to the best of our knowledge, there is no published systematic review summarizing the use of SNAs in oncology precision medicine and immunotherapy, which are considered new guidelines for oncology treatment. To this end, we summarized the notable advances in SNAs-based precision therapy and immunotherapy for tumors following a classification standard of different types of precise spatiotemporal control on active species by SNAs. Specifically, we focus on the structural diversity and programmability of SNAs. Finally, the challenges and possible solutions were discussed in the concluding remarks. This review will promote the rational design and development of SNAs for tumor-precise medicine and immunotherapy.

Inspired Beyond Nature: Three Decades of Spherical Nucleic Acids and Colloidal Crystal Engineering with DNA

The conception, synthesis, and invention of a nanostructure, now known as the spherical nucleic acid, or SNA, in 1996 marked the advent of a new field of chemistry. Over the past three decades, the SNA and its analogous anisotropic equivalents have provided an avenue for us to think about some of the most fundamental concepts in chemistry in new ways and led to technologies that are significantly impacting fields from medicine to materials science. A prime example is colloidal crystal engineering with DNA, the framework for using SNAs and related structures to synthesize programmable matter. Herein, we document the evolution of this framework, which was initially inspired by nature, and describe how it now allows researchers to chart paths to move beyond it, as programmable matter with real-world significance is envisioned and created.

Development of nucleic acid medicines based on chemical technology

Oligonucleotide-based therapeutics have attracted attention as an emerging modality that includes the modulation of genes and their binding proteins related to diseases, allowing us to take action on previously undruggable targets. Since the late 2010s, the number of oligonucleotide medicines approved for clinical uses has dramatically increased. Various chemistry-based technologies have been developed to improve the therapeutic properties of oligonucleotides, such as chemical modification, conjugation, and nanoparticle formation, which can increase nuclease resistance, enhance affinity and selectivity to target sites, suppress off-target effects, and improve pharmacokinetic properties. Similar strategies employing modified nucleobases and lipid nanoparticles have been used for developing coronavirus disease 2019 mRNA vaccines. In this review, we provide an overview of the development of chemistry-based technologies aimed at using nucleic acids for developing therapeutics over the past several decades, with a specific emphasis on the structural design and functionality of chemical modification strategies.

Aptamer-based colorimetric and lateral flow assay approaches for the detection of toxic metal ions, thallium(i) and lead(ii)

Thallium(i) and lead(ii) ions are heavy metals and extremely toxic. These metals are environmental pollutants, posing a severe risk to the environment and human health. In this study, two approaches were examined using aptamer and nanomaterial-based conjugates for thallium and lead detection. The first approach utilized an in-solution adsorption-desorption approach to develop colorimetric aptasensors for the detection of thallium(i) and lead(ii) using gold or silver nanoparticles. The second approach was the development of lateral flow assays, and their performance was tested with thallium (limit of detection is 7.4 μM) and lead ion (limit of detection is 6.6 nM) spiked into real samples. The approaches assessed are rapid, inexpensive, and time efficient with the potential to become the basis for future biosensor devices.

DNA-directed assembly of nanomaterials and their biomedical applications

In the past decades, DNA has been widely used in the field of nanostructures due to its unique programmable properties. Besides being used to form its own diverse structures such as the assembly of DNA origami, DNA can also be used for the assembly of nanostructures with other materials. In this review, different strategies for the functionalization of DNA on nanoparticle surfaces are listed, and the roles of DNA in the assembly of nanostructures as well as the influencing factors are discussed. Finally, the biomedical applications of DNA-assembled nanostructures were summarized. This review provided new insight into the application of DNA in nanostructure assembly.

DNA-Guided Metallization of Nanomaterials and Their Biomedical Applications

Precise control of the structure of metallic nanomaterials is critical for the advancement of nanobiotechnology. As DNA (deoxyribonucleic acid) can readily modify various moieties, such as sulfhydryl, carboxyl, and amino groups, using DNA as a directing ligand to modulate the morphology of nanomaterials is a promising strategy. In this review, we focus on the use of DNA as a template to control the morphology of metallic nanoparticles and their biomedical applications, discuss the use of DNA for the metallization of gold and silver, explore the factors that influence the process, and outline its biomedical applications. This review aims to provide valuable insights into the DNA-guided growth of nanomaterials. The challenges and future directions are also discussed.

Programming Nucleation and Growth in Colloidal Crystals Using DNA

Colloidal crystal engineering with DNA has advanced beyond controlling the lattice symmetry and parameters of ordered crystals to now tuning crystal habit and size. However, the predominately used slow-cooling procedure that enables faceted crystal habits also limits control over crystal size and uniformity because nucleation and growth cannot be separated. Here, we explore how DNA sequence design can be used to deliberately separate nucleation and growth in a given crystallization process. Specifically, two batches of complementary particles are created with one batch exhibiting perfectly complementary base pairs while the other has a strategically introduced mismatch. This design enables the weaker binding "growth" particles to participate in heterogeneous growth on the nucleates formed from the stronger binding "seed" particles, effectively eliminating secondary nucleation pathways. By eliminating secondary nucleation events, this approach improves crystal uniformity, as measured by polydispersity (from PDI = 0.201 to 0.091). By using this approach with two different particle cores (gold and silver), we show how core-shell colloidal crystals can be synthesized in a one-pot fashion. This work shows how tuning DNA interaction strength can profoundly impact crystal size, uniformity, and structure, parameters central to using such materials as device components.

Three-Dimensional Nucleic Acid Nanostructures Based on Self-Assembled Polymer-Oligonucleotide Conjugates of Comblike and Coil-Comb Chain Architectures

Spherical nucleic acids have emerged as a class of nanostructures, exhibiting a wide variety of properties, distinctly different from those of linear nucleic acids, and a plethora of applications in therapeutics and diagnostics. Herein, we report on preparation of 3D nucleic acid nanostructures, prepared by self-assembly of polymer-oligonucleotide conjugates. The latter are obtained by grafting multiple alkyne-functionalized oligonucleotide strands onto azide-modified homo-, block, and random (co)polymers of chloromethylstyrene via initiator-free click coupling chemistry to form conjugates of comblike and coil-comb chain architectures. The resulting conjugates are amphiphilic and form stable nanosized supramolecular structures in aqueous solution. The nanoconstructs are thoroughly investigated and a number of physical characteristics, in particular, molar mass, size, aggregation number, zeta potential, material density, number of oligonucleotide strands per particle, grafting density, and their relation to hallmark properties of spherical nucleic acids - biocompatibility, resistance against DNase I, cellular uptake without the need for transfection agents - are determined.

Array-based sensing and discrimination of segmented Baijiu using organic molecules-regulated PEI@Ag NPs@Ln as fluorescent probes

Quickly discriminating different segmented Baijiu can directly control its grade and indirectly affect the quality of the finished Baijiu. A fluorescence sensor array was constructed based on PEI-terminated silver nanoparticles and lanthanide metal ions (PEI@Ag NPs@Ln). Ag NPs were stably dispersed in the PEI-woven network, initially accompanied by excellent fluorescence signals. Organic molecules disrupted the PEI structure and dragged the Ag NPs out. The free Ag NPs sintered or aggregated with the diffusion, resulting in fluorescence quenching. The three lanthanide ions speed up the process, allowing different organic molecules to exhibit more distinct signals. Thus, this sensor was used to map 11 organic molecules' fingerprints and to discriminate segmented Baijiu. The whole process takes only 2 min. With the assistance of pattern recognition, segmented Baijiu from three cellars were successfully discriminated. Fast, effective and simple are highlights, which opens up its practical application potential in the detection field.

PD-L1 Aptamer-Functionalized Metal-Organic Framework Nanoparticles for Robust Photo-Immunotherapy against Cancer with Enhanced Safety

Immune checkpoint blockade has become a paradigm-shifting treatment modality to combat cancer, while conventional administration of immune checkpoint inhibitors, such as anti-PD-L1 antibody (α-PD-L1), often shows unsatisfactory immune responses and lead to severe immune-related adverse effects (irAEs). Herein, we develop a PD-L1 aptamer-based spherical nucleic acids (SNAs), which consists of oxaliplatin (OXA) encapsulated in a metal-organic framework nanoparticle core and a dense shell of aptPD-L1 (denoted as M@O-A). Upon light irradiation, this nanosystem enables concurrent photodynamic therapy (PDT), chemotherapy, and enhanced immunotherapy in one shot to inhibit both primary colorectal tumors and untreated distant tumors in mice. Notably, M@O-A shows scarcely any systemic immunotoxicity in a clinical irAEs-mimic transgenic mouse model. Collectively, this study presents a novel strategy for priming robust photo-immunotherapy against cancer with enhanced safety.

Symmetry-Breaking Dendrimer Synthons in Colloidal Crystal Engineering with DNA

Breaking symmetry in colloidal crystals is challenging due to the inherent chemical and structural isotropy of many nanoscale building blocks. If a non-particle component could be used to anisotropically encode such building blocks with orthogonal recognition properties, one could expand the scope of structural and compositional possibilities of colloidal crystals beyond what is thus far possible with purely particle-based systems. Herein, we report the synthesis and characterization of novel DNA dendrimers that function as symmetry-breaking synthons, capable of programming anisotropic and orthogonal interactions within colloidal crystals. When the DNA dendrimers have identical sticky ends, they hybridize with DNA-functionalized nanoparticles to yield three distinct colloidal crystals, dictated by dendrimer size, including a structure not previously reported in the field of colloidal crystal engineering, Si₂Sr. When used as symmetry-breaking synthons (when the sticky ends deliberately consist of orthogonal sequences), the synthesis of binary and ternary colloidal alloys with structures that can only be realized through directional interactions is possible. Furthermore, by modulating the extent of shape anisotropy within the DNA dendrimers, the local distribution of the nanoparticles within the crystals can be directed.

Nanoarchitectonics of Spherical Nucleic Acids with Biodegradable Polymer Cores: Synthesis and Evaluation

Spherical nucleic acids (SNAs) have gained significant attention due to their unique properties allowing them to overcome the challenges that face current nanocarriers used for gene therapies. The aim of this study is to synthesize and characterize polymer-oligonucleotide conjugates of different architecture and to evaluate the possibility of forming SNAs with biodegradable cores. Initially, two types of azide (multi)functional polyester-based (co)polymers were successfully synthesized and characterized. In the next step, short oligonucleotide strands were attached to the polymer chains applying the highly efficient and metal-free "click" reaction, thus forming conjugates with block or graft architecture. Both conjugates spontaneously self-assembled in aqueous media forming nanosized SNAs with a biodegradable polyester core and a surface of oligonucleotide chains as evidenced from dynamic and electrophoretic light scattering measurements. The nano-assemblies were in vitro evaluated for potential cytotoxicity. Furthermore, the interactions of the newly synthesized SNAs with membrane lipids were studied. The preliminary results indicate that both types of polymer-based SNAs are good candidates for potential application in gene therapy and that it is worth to be further evaluated.

Surface-enhanced Raman spectroscopy for characterization of filtrate portions of blood serum samples of typhoid patients

BACKGROUND

Surface-enhanced Raman spectroscopy (SERS) is explored to design a rapid screening method for the characterization and diagnosis of typhoid fever by employing filtrate fractions of blood serum samples obtained by centrifugal filtration with 50 KDa filters.

OBJECTIVES

The purpose of this study, to separate the filtrate portions of blood serum samples in this way contain proteins smaller than 50 kDa and removal of bigger size protein which allows to acquire the SERS spectral features of smaller proteins more effectively which are probably associated with typhoid disease. Disease caused by Salmonella typhi diagnose more effectively by using surface-enhanced Raman spectroscopy (SERS) and multivariate data analysis tools.

METHODS

SERS was used as a diagnostic tool for typhoid fever by comparison between healthy and diseased samples. For this purpose, all the samples were analyzed by comparing their SERS spectral features. Over the spectral range of 400-1800cm^-1, multivariate data analysis techniques such as Principal Component Analysis (PCA) and Partial Least Squares-Discriminant Analysis (PLS-DA) are applied to diagnose and differentiate different filtrate fractions of blood serum samples of patients of typhoid fever and healthy ones.

RESULTS

By comparing SERS spectra of healthy filtrate with that of filtrate of typhoid sample, the SERS spectral features associated with disease development are identified including PCA is found to be efficient for the qualitative differentiation of all of the samples analyzed. Moreover, PLS-DA successfully identified and classified healthy and typhoid positive blood serum samples with 97 % accuracy, 99 % specificity, 91 % sensitivity and 0.78 area under the receiver operating characteristic (AUROC) curve.

CONCLUSIONS

Surface enhanced Raman spectroscopy using silver nanoparticles SERS substrate, is found to be useful technique for the quick identification and evaluation of filtrate fractions of the blood serum samples of healthy and typhoid samples for disease diagnosis.

Gold-Silver Core-Shell Nanoparticle Crosslinking Mediated by Protease Activity for Colorimetric Enzyme Detection

Plasmonic nanoparticles produce a localized surface plasmon resonance (LSPR) under optical excitation. The LSPR of nanoparticles can shift in response to changes in the local dielectric environment and produce a color change. This color change can be observed by the naked eye due to the exceptionally large extinction coefficients (10⁸-10¹¹ M^-1 cm^-1) of plasmonic nanoparticles. Herein, we investigate the optical shifts (i.e., color change) of three unique gold-silver core-shell nanoparticle structures in response to changes in their dielectric environment upon nanoparticle aggregation. Aggregation is induced by a cysteine-containing peptide that has a sulfhydryl near its N and C termini, which crosslinks nanoparticles. Furthermore, we demonstrate that adding proline spacers between the cysteines impacts the degree of aggregation and, ultimately, the color response. Using this information, we construct a colorimetric enzyme assay, where the signal produced from nanoparticle aggregation is modulated by proteolysis. The degree of aggregation and the resulting optical shift can be correlated with enzyme concentration with high linearity (R² = 0.998). Overall, this study explores the optical properties of gold-silver core-shell nanoparticles in a dispersed vs aggregated state and leverages that information to develop an enzyme sensor with a spectral LOD of 0.47 ± 0.09 nM.

Silver nano-reporter enables simple and ultrasensitive profiling of microRNAs on a nanoflower-like microelectrode array on glass

MicroRNAs (miRNAs) are small non-coding RNAs with ~ 22 nucleotides, playing important roles in the post-transcriptional regulation of gene expression. The expression profiles of many miRNAs are closely related to the occurrence and progression of cancer and can be used as biomarkers for cancer diagnosis and prognosis. However, their intrinsic properties, such as short length, low abundance and high sequence homology, represent great challenges in miRNA detection of clinical samples. To overcome these challenges, we developed a simple, ultrasensitive detection platform of electrochemical miRNAs chip (e-miRchip) with a novel signal amplification strategy using silver nanoparticle reporters (AgNRs) for multiplexed, direct, electronic profiling of miRNAs. A two-step hybridization strategy was used to detect miRNAs, where the target miRNA hybridizes with a stem-loop probe to unlock the probe first, and the opened stem-loop can further hybridize with AgNRs for signaling amplification. To enhance the detection sensitivity, the gold nanoflower electrodes (GNEs) were constructed in the microaperture arrays of the e-miRchips by electroplating. With the optimal size of the GNEs, the e-miRchip showed excellent performance for miR-21 detection with a detection limit of 0.56 fM and a linear range extended from 1 fM to 10 pM. The e-miRchip also exhibited good specificity in differentiating the 3-base mismatched sequences of the target miRNA. In addition, the e-miRchip was able to directly detect miR-21 expression in the total RNA extracts or cell lysates collected from lung cancer cells and normal cells. This work demonstrated the developed e-miRchip as an efficient and promising miniaturized point-of-care diagnostic device for the early diagnosis and prognosis of cancers.

Graphical Abstract

Nucleic acid-based supramolecular structures: vesicular spherical nucleic acids from a non-phospholipid nucleolipid

Vesicular spherical nucleic acids are dynamic nucleic acid-based supramolecular structures that are held together via non-covalent bonds. They have promising applications as drug and nucleic acid delivery materials, diagnostic and imaging tools and platforms for development of various therapeutic schemes. In this contribution, we report on vesicular spherical nucleic acids, constructed from a non-phospholipid nucleolipid - an original hybrid biomacromolecule, composed of a hydrophobic residue, resembling that of the naturally occurring phospholipids, and a DNA oligonucleotide strand. The nucleolipid was synthesized by coupling of dibenzocyclooctyne-functionalized oligonucleotide and azidated 1,3-dihexadecyloxy-propane-2-ol via an azide-alkyne click reaction. In aqueous solution it spontaneously self-associated into nanosized supramolecular structures, identified as unilamellar vesicles composed of a self-closed interdigitated bilayer. Vesicular structures were also formed upon intercalation of the nucleolipid via its lipid-mimetic residue in the phospholipid bilayer membrane of liposomes prepared from readily available and FDA-approved lipids (1,2-dipalmitoyl-rac-glycero-3-phosphocholine and cholesterol). The vesicular structures are thoroughly investigated by light scattering (dynamic, static, and electrophoretic) and cryogenic TEM and the physical characteristics, in particular, number of strands per particle, grafting density, and conformation of the strands, were compared to those of reference spherical nucleic acids. Finally, the vesicular structures were shown to exhibit cellular internalization with no need of transfection agents and enhanced colloidal and nuclease stability.

Nanomaterials-enriched sensors for detection of chiral pharmaceuticals

Advancements in nanoscience and nanotechnology have opened new pathways to fabricate novel nanostructures with interesting properties that would be used for different applications. In this respect, nanostructures comprising chirality are one of the most rapidly developing research fields encompassing chemistry, physics and biology. Chirality, also known as mirror asymmetry, describes the geometrical property of an object that is not superimposable on its mirror image. This characteristic plays a crucial role because these identical forms of chiral species in pharmaceuticals or food additives may exhibit different effects on living organisms. Therefore, chiral analysis is an important field of modern chemical analysis in health-related industries that are reliant on the production of enantiomeric compounds involving pharmaceuticals. This review covers the recent advances dealing with the synthesis, design and advantageous analytical performance of nanomaterials-enriched sensors used for chiral pharmaceuticals. We conclude this review with the challenges existing in this research field and our perspectives on some potential strategies with cutting-edge approaches for the rational design of sensors for chiral pharmaceuticals. We expect this comprehensive review will inspire future studies in nanomaterials-enriched chiral sensors.

Plasmon-Enhanced Electrocatalysis of Conductive Polymer-Based Nano-Heterojunction for Small Molecule Metabolites Diagnostics

Conductive polymers are promising electrode candidates in the nonenzymatic catalytic detection of small molecule metabolites, due to the tunable electronic conductivity and versatile modifiability. However, the complex catalytic reaction pathway of conductive polymers results in lower detection sensitivity and a narrower linear range compared with clinical metal-based and carbon-based electrodes. Localized surface plasmon resonance (LSPR), characterized by deep strong light-matter coupling, has great potential in driving surface catalytic reactions at an ultrafast rate. Here, we constructed a salix argyracea-like polypyrrole nanowires/silver nanoparticles (PPy/AgNPs) heterojunction electrode using polydopamine as a dopant and chelator. Through cyclic voltammetry, the Mott-Schottky curve, and COMSOL simulation, we demonstrated that the LSPR-excited photocarriers enhanced PPy/AgNPs electrode electrocatalysis. Thus, the detection current response and linear range were significantly improved under the LSPR excitation when taking glucose and hydrogen peroxide as models of small molecule metabolites. Furthermore, we discussed the LSPR-enhanced detection mechanism of PPy/AgNPs electrode from the aspects of the Tafel slope, the apparent electron diffusion coefficient, and the charge transfer resistance. This strategy opens a new avenue toward the design of LSPR-enhanced conductive polymer electrodes.

Determination of the Concentration of Silver Atoms in Hydrosol Nanoparticles

In this work, we propose a new method for determining the concentration of silver atoms in hydrosols of nanoparticles (NPs) stabilized with various capping agents. The proposed method is based on the determination of IBT absorption in the UV region (a broad band with a weakly pronounced shoulder at ~250 nm). To determine the extinction coefficient at 250 nm, we synthesized silver nanoparticles with average sizes of 5, 10, and 25 nm, respectively. The prepared nanoparticles were characterized by TEM, HRTEM, electron diffraction, XRD, DLS, and UV-Vis spectroscopy. It has been shown that the absorption characteristics of spherical NPs are not significantly influenced by the hydrosol preparation method and the type of stabilizer used. For particles with a size of 5-25 nm, the molar extinction coefficient of Ag0 atoms was found to be equal to 3500 ± 100 L mol-1 cm-1 at a wavelength of 250 nm. The results of the theoretical calculations of the molar extinction coefficients for spherical nanoparticles are in good agreement with the experimental values. ICP-MS analysis confirmed the applicability of this method in the concentration range of 5 × 10-7-1 × 10-4 mol L-1.

Hollow spherical nucleic acid structures based on polymer-coated phospholipid vesicles

A feasible one pot synthesis of hollow spherical nucleic acids (SNAs) using phospholipid liposomes is reported. These constructs are synthesized in a chemically straightforward process involving formation of unilamellar liposomes, coating the liposomes with a thin cross-linked polymeric layer, and grafting the latter with short (about 20 bases) DNA oligonucleotide strands. They consist of vesicular cores, composed of readily available phospholipid (1,2-dipalmitoyl-sn-glycero-phosphocholine), whereas the strands are deliberately arranged on the surface of the vesicular entities. The initial vesicular structure and morphology are preserved during the coating and grafting reactions. The novel hollow/vesicular SNAs are characterized with a hydrodynamic radius and radius of gyration of 78.3 and 88.5 nm, respectively, and moderately negative (-14.2 mV) ζ potential. They carry thousands (5868) of oligonucleotide strands per vesicle, which are not strongly radially oriented and adopt an unextended conformation as anticipated from the smaller value of the grafting density compared to the critical grafting density at the transition to brush conformation. The constructs are practically devoid of toxicity and exhibit high binding affinity to complementary nucleic acids. Unlike any other nucleic acid structural motif, they cross the cell membrane and enter cells without the need of transfection agents.

Interfacial charge transfer complex formation between silver nanoparticles and aromatic amino acids

The optical properties of surface-modified silver nanoparticles (Ag NPs) with aromatic amino acids tryptophan (Trp) and histidine (His) were examined using the cluster model for density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. Also, the redistribution of electronic charges upon chemisorption of ligand molecules onto silver's surfaces is determined. The obtained theoretical data, on one side, undoubtedly indicate the the formation of an interfacial charge transfer (ICT) complex between silver and this type of ligand, and, on the other side, partial oxidation of surface silver atoms accompanied by an increase of electron density in ligand molecules. The ICT complex formation, based on noble metal nanoparticles, has never been reported previously to the best of our knowledge. The experimental spectroscopic measurements support the theoretical data. A new absorption band in the visible spectral range appears upon surface modification of Ag NPs, and, when exposed to air, oxidation of surface-modified Ag NPs is significantly faster than the oxidation of the unmodified ones.

Label-free fluorescent aptasensor for chloramphenicol based on hybridization chain reaction amplification and G-quadruplex/N-methyl mesoporphyrin IX complexation

The use of the broad-spectrum antibiotic chloramphenicol (CAP) in food is strictly regulated or banned in many countries. Herein, for the sensitive, rapid, and specific detection of CAP in milk, a label-free fluorescence strategy was established based on guanine (G)-quadruplex/N-methyl mesoporphyrin IX (NMM) complex formation and hybridization chain reaction (HCR) amplification. In this system, CAP can specifically bind to an aptamer (Apt) to release an Apt-C sequence from double-stranded DNA (Apt·Apt-C). Apt-C, can further hybridize with a functional hairpin DNA probe to release a primer sequence. The released primer sequence causes HCR and the formation of a nicked double-helix polymer, which contains G-quadruplex DNA. The recognition of G-quadruplex DNA by the NMM fluorochrome results in fluorescence enhancement. Consequently, CAP can be quantitatively detected by measuring the fluorescence intensity at 612 nm. The reliability of the aptasensor method was confirmed by comparison with an enzyme-linked immunosorbent assay. The proposed aptasensor was found to have a limit of detection of 0.8 pg mL-1 for CAP. Moreover, when the aptasensor was applied to the detection of CAP in milk samples, the average recoveries were 99.8-108.3% with relative standard deviations of 4.5-5.2%. Thus, this CAP detection method, which is rapid with high sensitivity and selectivity, has considerable potential for a wide range of food analysis applications.

Glutathione-Sensitive Nanoglue Platform with Effective Nucleic Acids Gluing onto Liposomes for Photo-Gene Therapy

Liposomal spherical nucleic acids possess a high density of nucleic acids, e.g., DNA, on a liposomal core. There are two approaches to conjugate DNA onto the zwitterionic liposomes, i.e., covalent and noncovalent conjugation, otherwise using cationic liposomes. However, complex and expensive DNA chemical modification methods need to seek a novel and easy-operating approach to decorating DNA onto liposomes. Inspired by the nanoparticle solution as nanoglues for gels and biological tissues, we use MnO₂ nanosheets to "glue" DNA onto liposomes without DNA modification. In tumor cells with a high glutathione concentration, MnO₂-based nanoglues are degraded, generating water-soluble Mn²⁺ ions, further "unglue" DNA (i.e., DNAzyme), and liposomes. Using the intelligent liposomal nanoglue (DNAzyme/MnO₂/Lip) combining glutathione-sensitive MnO₂ nanosheets, gene silencing agent DNAzyme, and photosensitizer Chlorin e6 (Ce6) in liposomes, effective photo-gene therapy was demonstrated.

A Critical Review of the Antimicrobial and Antibiofilm Activities of Green-Synthesized Plant-Based Metallic Nanoparticles

Metallic nanoparticles (MNPs) produced by green synthesis using plant extracts have attracted huge interest in the scientific community due to their excellent antibacterial, antifungal and antibiofilm activities. To evaluate these pharmacological properties, several methods or protocols have been successfully developed and implemented. Although these protocols were mostly inspired by the guidelines from national and international regulatory bodies, they suffer from a glaring absence of standardization of the experimental conditions. This situation leads to a lack of reproducibility and comparability of data from different study settings. To minimize these problems, guidelines for the antimicrobial and antibiofilm evaluation of MNPs should be developed by specialists in the field. Being aware of the immensity of the workload and the efforts required to achieve this, we set out to undertake a meticulous literature review of different experimental protocols and laboratory conditions used for the antimicrobial and antibiofilm evaluation of MNPs that could be used as a basis for future guidelines. This review also brings together all the discrepancies resulting from the different experimental designs and emphasizes their impact on the biological activities as well as their interpretation. Finally, the paper proposes a general overview that requires extensive experimental investigations to set the stage for the future development of effective antimicrobial MNPs using green synthesis.

Ultrastable Silver Nanoparticles for Rapid Serology Detection of Anti-SARS-CoV-2 Immunoglobulins G

Dipstick assays using silver nanoparticles (AgNPs) stabilized by a thin calix[4]arene-based coating were developed and used for the detection of Anti-SARS-CoV-2 IgG in clinical samples. The calixarene-based coating enabled the covalent bioconjugation of the SARS-CoV-2 Spike Protein via the classical EDC/sulfo-NHS procedure. It further conferred remarkable stability to the resulting bioconjugated AgNPs, as no degradation was observed over several months. In comparison with lateral-flow immunoassays (LFIAs) based on classical gold nanoparticles, our AgNP-based system constitutes a clear step forward, as the limit of detection for Anti-SARS-CoV-2 IgG was reduced by 1 order of magnitude and similar signals were observed with 10 times fewer particles. In real clinical samples, the AgNP-based dipstick assays showed impressive results: 100% specificity was observed for negative samples, while a sensitivity of 73% was determined for positive samples. These values match the typical sensitivities obtained for reported LFIAs based on gold nanoparticles. These results (i) represent one of the first examples of the use of AgNP-based dipstick assays in the case of real clinical samples, (ii) demonstrate that ultrastable calixarene-coated AgNPs could advantageously replace AuNPs in LFIAs, and thus (iii) open new perspectives in the field of rapid diagnostic tests.

Spherical Nucleic Acids as Precision Therapeutics for the Treatment of Cancer-From Bench to Bedside

Spherical Nucleic Acids (SNAs) emerged as a new class of nanotherapeutics consisting of a nanoparticle core densely functionalized with a shell of radially oriented synthetic oligonucleotides. The unique three-dimensional architecture of SNAs protects the oligonucleotides from nuclease-mediated degradation, increases oligonucleotide bioavailability, and in the absence of auxiliary transfection agents, enables robust uptake into tumor and immune cells through polyvalent association with cell surface pattern recognition receptors. When composed of gene-regulatory small interfering (si)RNA or immunostimulatory DNA or RNA oligonucleotides, SNAs silence gene expression and induce immune responses superior to those raised by the oligonucleotides in their "free" form. Early phase clinical trials of gene-regulatory siRNA-based SNAs in glioblastoma (NCT03020017) and immunostimulatory Toll-like receptor 9 (TLR9)-agonistic SNAs carrying unmethylated CpG-rich oligonucleotides in solid tumors (NCT03086278) have shown that SNAs represent a safe, brain-penetrant therapy for inhibiting oncogene expression and stimulating immune responses against tumors. This review focuses on the application of SNAs as precision cancer therapeutics, summarizes the findings from first-in-human clinical trials of SNAs in solid tumors, describes the most recent preclinical efforts to rationally design next-generation multimodal SNA architectures, and provides an outlook on future efforts to maximize the anti-neoplastic activity of the SNA platform.

Sub-1.5 nm-gapped heterodimeric plasmonic nanomolecules

A whole set of plasmonic nanodimers with prescribed binary compositions are constructed in solution to enable symmetry-broken strong plasmonic coupling.

Molecularly pure miktoarm spherical nucleic acids: preparation and usage as a scaffold for abiotic intracellular catalysis

We present a fullerene-based strategy that allows the synthesis of molecularly pure miktoarm spherical nucleic acids (SNAs) with diverse structures, which, with post-functionalization, could serve as efficient scaffolds for intracellular catalysis. The SNA structure promotes cell permeability, nucleic acid stability, and catalytic efficiency, making the platform ideal for in cellulo reactions. Consequently, the tris(triazole)-bearing miktoarm SNA was able to effectively mediate intracellular copper-catalyzed alkyne-azide cycloaddition at nanomolar level of copper, and facilitate the same reaction in live zebrafish.

Pyrophosphate-Enhanced Oxidase Activity of Cerium Oxide Nanoparticles for Colorimetric Detection of Nucleic Acids

In recent years, cerium oxide (CeO₂) nanoparticles (NPs) have drawn significant attention owing to their intrinsic enzyme mimetic properties, which make them powerful tools for biomolecular detection. In this work, we evaluated the effect of pyrophosphate (PPi) on the oxidase activity of CeO₂ NPs. The presence of PPi was found to enhance the oxidase activity of CeO₂ NPs, with enhanced colorimetric signals. This particular effect was then used for the colorimetric detection of target nucleic acids. Overall, the PPi-enhanced colorimetric signals of CeO₂ NPs oxidase activity were suppressed by the presence of the target nucleic acids. Compared with previous studies using CeO₂ NPs only, our proposed system significantly improved the signal change (ca. 200%), leading to more sensitive and reproducible colorimetric analysis of target nucleic acids. As a proof-of-concept study, the proposed system was successfully applied to the highly selective and sensitive detection of polymerase chain reaction products derived from Klebsiella pneumoniae. Our findings will benefit the rapid detection of nucleic acid biomarkers (e.g., pathogenic bacterial DNA or RNA) in point-of-care settings.

Novel Biorecognition Elements against Pathogens in the Design of State-of-the-Art Diagnostics

Infectious agents, especially bacteria and viruses, account for a vast number of hospitalisations and mortality worldwide. Providing effective and timely diagnostics for the multiplicity of infectious diseases is challenging. Conventional diagnostic solutions, although technologically advanced, are highly complex and often inaccessible in resource-limited settings. An alternative strategy involves convenient rapid diagnostics which can be easily administered at the point-of-care (POC) and at low cost without sacrificing reliability. Biosensors and other rapid POC diagnostic tools which require biorecognition elements to precisely identify the causative pathogen are being developed. The effectiveness of these devices is highly dependent on their biorecognition capabilities. Naturally occurring biorecognition elements include antibodies, bacteriophages and enzymes. Recently, modified molecules such as DNAzymes, peptide nucleic acids and molecules which suffer a selective screening like aptamers and peptides are gaining interest for their biorecognition capabilities and other advantages over purely natural ones, such as robustness and lower production costs. Antimicrobials with a broad-spectrum activity against pathogens, such as antibiotics, are also used in dual diagnostic and therapeutic strategies. Other successful pathogen identification strategies use chemical ligands, molecularly imprinted polymers and Clustered Regularly Interspaced Short Palindromic Repeats-associated nuclease. Herein, the latest developments regarding biorecognition elements and strategies to use them in the design of new biosensors for pathogens detection are reviewed.

L-cysteine capped silver nanoparticles as chiral recognition sensor for ketoprofen enantiomers

A simple, inexpensive but effective approach for visual chiral recognition of ketoprofen enantiomers was developed using L-cysteine capped silver nanoparticles (L-Cys-AgNPs) as a colorimetric sensor. Upon the addition of R-ketoprofen to L-Cys-AgNPs, rapid aggregation occurred, and the solution changed color from yellow to green. However, the presence of S-ketoprofen did not induce any color change. The results were characterized using UV-Vis, FESEM, FT-IR, SERS, and zeta potential measurements. The chiral assay described in this work is easily distinguished with the naked eyes or using a UV-Vis spectrometer. The sensor revealed a good linear response to ketoprofen enantiomers in the concentration range of 8.33-33.3 μM with a detection limit of 4.52 μM and relative standard deviation of 3.73%. The proposed method was utilized for the determination of ketoprofen racemic mixtures in water samples and commercial tablets. The method excels by its simplicity, low cost, and good availability of materials.

Patterns from drops drying on inclined substrates

The coffee ring effect results from the migration of particles in a drying particle laden drop and their subsequent deposition at the three phase contact line. The evaporative flux during the drying of sessile drops and the spatial distribution of particles in the coffee ring patterns exhibit azimuthal symmetry. It is possible to break this symmetry with the help of gravity by simply manipulating the inclination of the substrate on which the colloidal droplet undergoes drying. However, the effect of particle size, substrate wettability and inclination angle on the extent of asymmetry in the spatial distribution of particles over the deposit patterns has not been explored and is the subject of the current work. Our experiments on the drying of aqueous dispersions of polystyrene particles show that (i) asymmetry in the deposition of particles is observed irrespective of the diameter of the dispersed particles in the drying drop (ii) the degree of asymmetry increases with a decrease in wettability of the drop on the substrate and (iii) it is a non-monotonic function of the inclination angle of the substrate. These results indicate the possibility of additional particle transport mechanisms working in tandem with evaporation driven capillary flows and demand further investigation of the physics of pattern formation in drops drying on oriented substrates.

Surface-enhanced Raman spectroscopy for the identification of tigecycline-resistant E. coli strains

Tigecycline (TGC) is recognised as last resort of drugs against several antibiotic-resistant bacteria. Bacterial resistance to tigecycline due to presence of plasmid-mediated mobile TGC resistance genes (tet X3/X4) has broken another defense line. Therefore, rapid and reproducible detection of tigecycline-resistant E. coli (TREC) is required. The current study is designed for the identification and differentiation of TREC from tigecycline-sensitive E. coli (TSEC) by employing SERS by using Ag NPs as a SERS substrate. The SERS spectral fingerprints of E. coli strains associated directly or indirectly with the development of resistance against tigecycline have been distinguished by comparing SERS spectral data of TSEC strains with each TREC strain. Moreover, the statistical analysis including Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA) and Partial Least Squares-Discriminant Analysis (PLS-DA) were employed to check the diagnostic potential of SERS for the differentiation among TREC and TSEC strains. The qualitative identification and differentiation between resistant and sensitive strains and among individual strains have been efficiently done by performing both PCA and HCA. The successful discrimination among TREC and TSEC at the strain level is performed by PLS-DA with 98% area under ROC curve, 100% sensitivity, 98.7% specificity and 100% accuracy.

A first-in-human phase 0 clinical study of RNA interference-based spherical nucleic acids in patients with recurrent glioblastoma

Glioblastoma (GBM) is one of the most difficult cancers to effectively treat, in part because of the lack of precision therapies and limited therapeutic access to intracranial tumor sites due to the presence of the blood-brain and blood-tumor barriers. We have developed a precision medicine approach for GBM treatment that involves the use of brain-penetrant RNA interference-based spherical nucleic acids (SNAs), which consist of gold nanoparticle cores covalently conjugated with radially oriented and densely packed small interfering RNA (siRNA) oligonucleotides. On the basis of previous preclinical evaluation, we conducted toxicology and toxicokinetic studies in nonhuman primates and a single-arm, open-label phase 0 first-in-human trial (NCT03020017) to determine safety, pharmacokinetics, intratumoral accumulation and gene-suppressive activity of systemically administered SNAs carrying siRNA specific for the GBM oncogene Bcl2Like12 (Bcl2L12). Patients with recurrent GBM were treated with intravenous administration of siBcl2L12-SNAs (drug moniker: NU-0129), at a dose corresponding to 1/50th of the no-observed-adverse-event level, followed by tumor resection. Safety assessment revealed no grade 4 or 5 treatment-related toxicities. Inductively coupled plasma mass spectrometry, x-ray fluorescence microscopy, and silver staining of resected GBM tissue demonstrated that intravenously administered SNAs reached patient tumors, with gold enrichment observed in the tumor-associated endothelium, macrophages, and tumor cells. NU-0129 uptake into glioma cells correlated with a reduction in tumor-associated Bcl2L12 protein expression, as indicated by comparison of matched primary tumor and NU-0129-treated recurrent tumor. Our results establish SNA nanoconjugates as a potential brain-penetrant precision medicine approach for the systemic treatment of GBM.

An Enhanced Lateral Flow Assay Based on Aptamer-Magnetic Separation and Multifold AuNPs for Ultrasensitive Detection of Salmonella Typhimurium in Milk

In this paper, a novel and ultrasensitive lateral flow assay (LFA) based on aptamer-magnetic separation, and multifold Au nanoparticles (AuNPs) was developed for visual detecting Salmonella enterica ser. Typhimurium (S. Typhimurium). The method realized magnetic enrichment and signal transduction via magnetic separation and achieved signal amplification through hybridizing AuNPs-capture probes and AuNPs-amplification probes to form multifold AuNPs. Two different thiolated single-strand DNA (ssDNA) on the AuNPs-capture probe played different roles. One was combined with the AuNPs-amplification probe on the conjugate pad to achieve enhanced signals. The other was connected to transduction ssDNA1 released by aptamer-magnetic capture of S. Typhimurium, and captured by the T-line, forming a positive signal. This method had an excellent linear relationship ranging from 8.6 × 102 CFU/mL to 8.6 × 107 CFU/mL with the limit of detection (LOD) as low as 8.6 × 100 CFU/mL in pure culture. In actual samples, the visual LOD was 4.1 × 102 CFU/mL, which did not carry out nucleic acid amplification and pre-enrichment, increasing three orders of magnitudes than unenhanced assays with single-dose AuNPs and no magnetic separation. Furthermore, the system showed high specificity, having no reaction with other nontarget strains. This visual signal amplificated system would be a potential platform for ultrasensitive monitoring S. Typhimurium in milk samples.

Construction of silver nanoparticles by the triple helical polysaccharide from black fungus and the antibacterial activities

Size controllable silver nanoparticles (AgNPs) were synthesized in situ on the polysaccharides-based nanotubes, which were formed by the triple-helix polysaccharide extracted from black fungus (AF1). The results of transmission electron microscope (TEM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) proved that AgNPs with the size from 10-25 nm were uniformly dispersed on the surface of AF1 dendritic nanotubes without affecting their tubular morphology. Moreover, due to the tubular structure, the loaded silver content of the composites (AgNPs and AF1 nanotube, AF1-Ag) could reach about 50% by thermogravimetric analysis (TG) evaluation. Thus, the smaller size of AgNPs and higher silver loading content suggest that the composites could be applied in the biomedical field. The antibacterial properties of AF1-Ag were evaluated as an example in the present work. As expected, the culture medium contained a few of AF1-Ag (10% ω%, c = 50 μg/mL) exhibited obvious antibacterial properties, and the effect of bacteriostasis increased with the increase of the amount of supported silver content. Taken together, the AF1-Ag with good antibacterial activity and good stability has the potential to be applied in the antibacterial field.

Interfacial interactions of SERS-active noble metal nanostructures with functional ligands for diagnostic analysis of protein cancer markers

Noble metal nanostructures with designed hot spots have been widely investigated as surface-enhanced Raman spectroscopy (SERS)-active substrates, particularly for selective and sensitive detection of protein cancer markers. For specific target recognition and efficient signal amplification, SERS probe design requires a choice of SERS-active nanostructures as well as their controlled functionalization with Raman dyes and target recognition entities such as antibodies. However, the chemical conjugation of antibodies and Raman dyes to SERS substrates has rarely been discussed to date, despite their substantial roles in detection schemes. The interfacial interactions of metal nanostructures with functional ligands during conjugation are known to be strongly influenced by the various chemical and physical properties of the ligands, such as size, molecular weight, surface charge, 3-dimensional structures, and hydrophilicity/hydrophobicity. In this review, we discuss recent developments in the design of SERS probes over the last 4 years, focusing on their conjugation chemistry for functionalization. A strong preference for covalent bonding is observed with Raman dyes having simpler molecular structures, whereas more complicated ones are non-covalently adsorbed. Antibodies are both covalently and non-covalently bonded to nanostructures, depending on their activity in the SERS probes. Considering that ligand conjugation is highly important for chemical stability, biocompatibility, and functionality of SERS probes, this review is expected to expand the understanding of their interfacial design, leading to SERS as one of the most promising spectroscopic analytical tools for the early detection of protein cancer markers.

Development of Antibody-Conjugated Gold and Magnetic Nanocomposites for the Colorimetric Detection of Influenza A Virus

A novel approach for the detection of influenza virus is of paramount importance for quick diagnosis and therapy. In this study monoclonal antibody (mAb)-conjugated MNPs/AuNPs were developed to detect the H1N1 virus. MNPs and AuNPs were synthesized and loaded with mAbs. The UV-vis spectra exhibited absorbance at 528 nm. XRD revealed the presence of crystalline particles with various diffraction peaks. FTIR confirmed the occurrence of capping molecules in the synthesized NPs. NP stability was evidenced by zeta measurements. The shape and size (mean size 15 nm) of the NPs were determined using SEM and transmission electron microscopy (TEM). In this study the mAb–AuNPs produced a redshift in the absorption spectrum due to plasmon coupling. The absorption increased when H1N1 concentration increased from 0 to 5.0 ng/mL, with the detection limit being 0.05 ng/mL. The sensitivity of mAb–AuNPs was greater than that of ELISA. Since the mAb-AuNP-based colorimetric immunosensor is simple, cost-effective, and rapidly detects H1N1, it has good prospects in pharmaceuticals and clinical diagnosis.

Aptamer-Based Detection of Circulating Targets for Precision Medicine

The past decade has witnessed ongoing progress in precision medicine to improve human health. As an emerging diagnostic technique, liquid biopsy can provide real-time, comprehensive, dynamic physiological and pathological information in a noninvasive manner, opening a new window for precision medicine. Liquid biopsy depends on the sensitive and reliable detection of circulating targets (e.g., cells, extracellular vesicles, proteins, microRNAs) from body fluids, the performance of which is largely governed by recognition ligands. Aptamers are single-stranded functional oligonucleotides, capable of folding into unique tertiary structures to bind to their targets with superior specificity and affinity. Their mature evolution procedure, facile modification, and affinity regulation, as well as versatile structural design and engineering, make aptamers ideal recognition ligands for liquid biopsy. In this review, we present a broad overview of aptamer-based liquid biopsy techniques for precision medicine. We begin with recent advances in aptamer selection, followed by a summary of state-of-the-art strategies for multivalent aptamer assembly and aptamer interface modification. We will further describe aptamer-based micro-/nanoisolation platforms, aptamer-enabled release methods, and aptamer-assisted signal amplification and detection strategies. Finally, we present our perspectives regarding the opportunities and challenges of aptamer-based liquid biopsy for precision medicine.