Fluorescent nanoparticles for intracellular sensing: A review

Adding colour to ion-selective membranes

An idea of using ion-exchanger salt containing optically active cations to prepare ion-selective membranes is proposed. Although the presence of an ion-exchanger in the composition of neutral ionophore based sensors is necessary, the choice of available salts for cation-selective sensors preparation, is usually limited to sodium or potassium compounds. In this work we propose application of an alternative salt, using a cation optically active both in absorption and emission mode as a mobile one. Thus, coloured ion-selective membranes can be obtained. This in turn opens new possibilities of monitoring the state of the receptor layer as well as allows direct analytical application of ion-selective membranes in simple optical mode with all benefits related to eliminating the necessity of using reference electrodes. As a model system Nile blue derivative of tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ion-exchanger was prepared and used to obtain potassium or calcium selective sensors. Selective exchange of ions between the membrane and solution, leading to an increase in optical signal of the solution, can be used to quantify the presence of analyte ions. Thus the sensor pretreatment process is becoming a source of analytical information. The applicability of this approach was verified in determining the presence of potassium ions in the vast majority of interfering ions, e.g. present as impurities in the reagent grade calcium chloride. The resulting potassium ions contents was well comparable with values obtained in course of ICP-MS approach.

Direct covalent attachment of fluorescent molecules on plasma polymerized nanoparticles: a simplified approach for biomedical applications

Polymeric nanoparticles surface functionalised with fluorescent molecules hold significant potential for advancing diagnostics and therapeutic delivery. Despite their promise, challenges persist in achieving robust attachment of fluorescent molecules for real-time tracking. Weak physical adsorption, pH-dependent electrostatic capture, and hydrophobic interactions often fail to achieve stable attachment of fluorescent markers. While covalent attachment offers stability, it often entails laborious multi-step wet-chemistry processes. This work demonstrates that plasma polymerised nanoparticles (PPNs) can directly and covalently attach fluorescent molecules with no need for additional interim treatment processes. For the first time, we provide evidence indicating the formation of covalent bonds between the fluorescent molecules and PPN surfaces. Two model fluorescent molecules, fluorescein isothiocyanate (FITC) and Nile blue (NB), were attached to PPNs in a one-step process. The attached molecules remained on nanoparticle surfaces even after detergent washing, as confirmed by a combination of X-ray photoelectron spectroscopy (XPS), fluorescence spectroscopy, flow cytometry, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) data. The robust attachment of fluorescent molecules on PPNs ensures their stability and functionality, enhancing the potential of these fluorescently labelled nanoparticles for diagnostic, therapeutic, and imaging applications.

Gold nanoclusters stabilized with dopa-containing ligands: Catalyst-indicator integrated probe for tumor cell screening

Elevated hydrogen peroxide (H2O2) levels not only inflict cellular damage but also serve as a harbinger for various diseases. Tumor cells, in particular, often exhibit an abundance of H2O2. Hence, the detection of this pivotal molecule assumes paramount importance in monitoring physiological states and expediting cancer diagnosis. To this end, we have ingeniously devised an enzyme-free and monomeric system for intracellular H2O2 detection. Our astute selection of dopa-containing peptidomimetics, replete with ortho-bisphenol and amino acid moieties, has engendered the synthesis of distinctive fluorescent gold nanoclusters (AuNCs). These nanoclusters not only function as a peroxidase-like catalyst, catalyzing the decomposition of H2O2 into hydroxyl radicals (·OH), but also serve as an indicator, with their fluorescence quenched in response to varying H2O2 concentrations. Experimental results evince that our GDpE-AuNCs exhibit remarkable sensitivity, boasting a detection limit of 0.49 μM and a linear range of 5-1000 μM. Moreover, the amalgamation of catalyst and indicator within a single structure, facilitating efficient cellular uptake, engenders intracellular H2O2 detection and discernment of tumor cells. This pioneering approach bequeaths a valuable assay probe for monitoring physiological states and ushering in early disease diagnosis.

Application of rare earth elements in dual-modality molecular probes

The unique 4f subshell electronic structure of rare earth elements endows them with exceptional properties in electrical, magnetic, and optical domains. These properties include prolonged fluorescence lifetimes, large Stokes shifts, distinctive spectral bands, and strong resistance to photobleaching, making them ideal for the synthesis of molecular probes. Each imaging technique possesses unique advantages and specific applicabilities but also inherent limitations due to its operational principles. Dual-modality molecular probes effectively address these limitations, particularly in applications involving high-resolution Magnetic Resonance Imaging (MRI) such as MRI/OI, MRI/PET, MRI/CT, and MRI/US. This review summarizes the applications, advantages, challenges, and current research status of rare earth elements in these four dual imaging modalities, providing a theoretical basis for the future development and application of rare earth elements in the field of dual-modality molecular probes.

Multi-deformable interpenetrating network thermosensitive hydrogel fluorescent device for real-time and visual detection of nitrite

Functionalized thermosensitive hydrogel materials exhibit excellent properties for the fabrication of sensing devices that enable real-time visual detection of food safety duo to their good plasticity and powerful loading capacity. Here, a ratiometric fluorescent device based on an interpenetrating network (IPN) thermosensitive hydrogel was designed to embed functionalized Au nanoclusters (Au NCs) and Blue Carbon dots (BCDs) composites in a multi-network structure to build a sensitive hazardous material nitrite (NO2-) chemsensor. The hydrogel was utilized poloxamer 407 (P407), lignin and cellulose to form stable IPN structure, which resulted in complementation and synergy, thereby strengthening its porous network structure. The combination of fluorescent nanoprobes with the porous network structure has the potential to enhance stable fluorescence signals and improve sensing sensitivity. Moreover, the thermosensitive liquid-solid transition characteristics of the hydrogel facilitate its preparation into diverse sensing devices following curing at room temperature. The hydrogel device, when combined with a smartphone system, converted image information into data information, thereby enabling the accurate quantification of NO2- with a detection limit of 9.38 nM in 2 s. The designed multi-functional hydrogel device is capable of real-time differentiation of NO2- dosage with the naked eye, offering a high-contrast, rapid-response sensing methodology for visual assessment of food freshness. This research contributes to the expansion of hydrogel materials applications and the detection of hazardous materials in food safety.

Conducting polymer functionalization in search of advanced materials in ionometry: ion-selective electrodes and optodes

Functionalized conducting polymers (FCPs) have recently garnered attention as ion-selective sensor materials, surpassing their intrinsic counterparts due to synergistic effects that lead to enhanced electrochemical and analytical parameters. Following a brief introduction of the fundamental concepts, this article provides a comprehensive review of the recent developments in the application of FCPs in ion-selective electrodes (ISEs) and ion-selective optodes (ISOs), particularly as ion-to-electron transducers, optical transducers, and ion-selective membranes. Utilizing FCPs in these devices offers a promising avenue for detecting and measuring ions in various applications, regardless of the sample nature and composition. Research has focused on functionalizing different conducting polymers, such as polyaniline and polypyrrole, through strategies such as doping and derivatization to alter their hydrophobicity, conductance, redox capacitance, surface area, pH sensitivity, gas and light sensitivity, etc. These modifications aim to enhance performance outcomes, including potential stability/emission signal stability, reproducibility and low detection limits. The advancements have led to the transition of ISEs from conventional zero-current potentiometric ion sensing to innovative current-triggered sensing approaches, enabling calibration-free applications and emerging concepts such as opto-electro dual sensing systems. The intrinsic pH cross-response and instability of the optical signal of ISOs have been overcome through the novel optical signal transduction mechanisms facilitated by FCPs. In this review, the characteristics of materials, functionalization approaches, particular implementation strategies, specific performance outcomes and challenges faced are discussed. Consolidating dispersed information in the field, the in-depth analysis presented here is poised to drive further innovations by broadening the scope of ion-selective sensors in real-world scenarios.

Self-Assembly of Hydrophobic Hyperbranched PLMA Homopolymer with -COOH End Groups as Effective Nanocarriers for Bioimaging Applications

Nanomedicine is a discipline of medicine that applies all aspects of nanotechnology strategies and concepts for treatment and screening possibilities. Synthetic polymer nanostructures are among the many nanomedicine formulations frequently studied for their potential as vectors. Bioimaging is a valuable diagnostic tool, thus, there is always a demand for new excipients/nanocarriers. In this study, hydrophobic hyperbranched poly(lauryl methacrylate) (PLMA) homopolymers comprised of highly hydrophobic LMA moieties with -COOH polar end groups were synthesized by employing reversible addition-fragmentation chain transfer (RAFT) polymerization. Ethylene glycol dimethacrylate (EGDMA) was utilized as the branching agent. End groups are incorporated through the RAFT agent utilized. The resulting amphiphilic hyperbranched polymer was molecularly characterized by size exclusion chromatography (SEC), Fourier transformation infrared spectroscopy (FT-IR), and 1H-NMR spectroscopy. Pyrene, curcumin, and IR-1048 dye were hydrophobic payload molecules successfully encapsulated to show how adaptable these homopolymer nanoparticles (prepared by nanoprecipitation in water) are as dye nanocarriers. This study demonstrates a simple way of producing excipients by generating polymeric nanoparticles from an amphiphilic, hyperbranched, hydrophobic homopolymer, with a low fraction of polar end groups, for bioimaging purposes.

Programmable Colloids with Analogous Hypercoordination Complex Architectures

Colloidal molecule clusters (CMCs) are promising building blocks with molecule-like symmetry, offering exceptional synergistic properties for applications in plasmonics and catalysis. Traditional CMC fabrication has been limited to simple molecule-like structures utilizing isotropic particles. Here, we employ molecular dynamics simulation to investigate the co-assembly of anisotropic nanorods (NRs) and the stimulus-responsive polymer (SRP) via reversible adsorption. The results of the simulation show that it is possible to fabricate hypercoordination complex structures with high symmetry from the co-assembly of NRs and the SRP, even in analogy to the Th(BH4)4 structure. The coordination number of these CMCs can be precisely programmed by adjusting the shape and size of the ends of the NRs and the SRP cohesion energy. Furthermore, a finite-difference time-domain simulation indicates these hypercoordination structures exhibit significantly enhanced optical activity and plasmonic coupling effects. These findings introduce a new design approach for complex molecule-like structures utilizing anisotropic nanoparticles and may expand the applications of CMCs in photonics.

Photoswitching the fluorescence of nanoparticles for advanced optical applications

The dynamic optical response properties and the distinct features of nanomaterials make photoswitchable fluorescent nanoparticles (PF NPs) attractive candidates for advanced optical applications. Over the past few decades, the design of PF NPs by coupling photochromic and fluorescent motifs at the nanoscale has been actively pursued, and substantial efforts have been made to exploit their potential applications. In this perspective, we critically summarize various design principles for fabricating these PF NPs. Then, we discuss their distinct optical properties from different aspects by highlighting the capability of NPs in fabricating new, robust photoswitch systems. Afterwards, we introduce the pivotal role of PF NPs in advanced optical applications, including sensing, anti-counterfeiting and imaging. Finally, current challenges and future development of PF NPs are briefly discussed.

Photoluminescence from FRET pairs coupled with Mie-resonant silicon nanospheres

Optically resonant nanoparticles decorated with donor-acceptor molecular pairs have been attracting attention for applications as nanoprobes in bioimaging and biosensing. We produced composite nanoparticles composed of donor-acceptor molecular pairs and silicon nanospheres (Si NSs) with diameters of 100-200 nm exhibiting Mie resonances in the visible range and studied the effect of Mie resonances on their photoluminescence properties. We showed that the photoluminescence spectra are strongly modified by Mie resonances and the spectral shape is controlled in a wide range by the Si NS size; by controlling the size, we can achieve the photoluminescence maximum from that of a donor molecule to that of an acceptor molecule almost continuously. From the photoluminescence decay properties in combination with theoretical calculations, we showed that the observed strong modification of the spectral shape is mainly due to the Purcell effect on donor and acceptor molecules, and the effect of Mie resonances on the Förster resonance energy transfer (FRET) rate is relatively small. We also showed that because of the large Purcell effect and the small FRET rate enhancement, Mie resonances decrease the FRET efficiency.

Exploring the current landscape of chitosan-based hybrid nanoplatforms as cancer theragnostic

In the last decade, investigators have put significant efforts to develop several diagnostic and therapeutic strategies against cancer. Many novel nanoplatforms, including lipidic, metallic, and inorganic nanocarriers, have shown massive potential at preclinical and clinical stages for cancer diagnosis and treatment. Each of these nano-systems is distinct with its own benefits and limitations. The need to overcome the limitations of single-component nano-systems, improve their morphological and biological features, and achieve multiple functionalities has resulted in the emergence of hybrid nanoparticles (HNPs). These HNPs integrate multicomponent nano-systems with diagnostic and therapeutic functions into a single nano-system serving as promising nanotools for cancer theragnostic applications. Chitosan (CS) being a mucoadhesive, biodegradable, and biocompatible biopolymer, has emerged as an essential element for the development of HNPs offering several advantages over conventional nanoparticles including pH-dependent drug delivery, sustained drug release, and enhanced nanoparticle stability. In addition, the free protonable amino groups in the CS backbone offer flexibility to its structure, making it easy for the modification and functionalization of CS, resulting in better drug targetability and cell uptake. This review discusses in detail the existing different oncology-directed CS-based HNPs including their morphological characteristics, in-vitro/in-vivo outcomes, toxicity concerns, hurdles in clinical translation, and future prospects.

Chemical Reactions in Living Systems

The term "in vivo ("in the living") chemistry" refers to chemical reactions that take place in a complex living system such as cells, tissue, body liquids, or even in an entire organism. In contrast, reactions that occur generally outside living organisms in an artificial environment (e.g., in a test tube) are referred to as in vitro. Over the past decades, significant contributions have been made in this rapidly growing field of in vivo chemistry, but it is still not fully understood, which transformations proceed efficiently without the formation of by-products or how product formation in such complex environments can be characterized. Potential applications can be imagined that synthesize drug molecules directly within the cell or confer new cellular functions through controlled chemical transformations that will improve the understanding of living systems and develop new therapeutic strategies. The guiding principles of this contribution are twofold: 1) Which chemical reactions can be translated from the laboratory to the living system? 2) Which characterization methods are suitable for studying reactions and structure formation in complex living environments?

Fluorescence-Based Mono- and Multimodal Imaging for In Vivo Tracking of Mesenchymal Stem Cells

The advancement of stem cell therapy has offered transformative therapeutic outcomes for a wide array of diseases over the past decades. Consequently, stem cell tracking has become significant in revealing the mechanisms of action and ensuring safe and effective treatments. Fluorescence stands out as a promising choice for stem cell tracking due to its myriad advantages, including high resolution, real-time monitoring, and multi-fluorescence detection. Furthermore, combining fluorescence with other tracking modalities-such as bioluminescence imaging (BLI), positron emission tomography (PET), photoacoustic (PA), computed tomography (CT), and magnetic resonance (MR)-can address the limitations of single fluorescence detection. This review initially introduces stem cell tracking using fluorescence imaging, detailing various labeling strategies such as green fluorescence protein (GFP) tagging, fluorescence dye labeling, and nanoparticle uptake. Subsequently, we present several combinations of strategies for efficient and precise detection.

Tetraphenylethylene-Based Photoluminescent Self-Assembled Nanoparticles: Preparation and Biological Evaluation

The conjugation of tetraphenylethylene (TPE) with podophyllotoxin, N-desacetylthiocolchicine, and cabazitaxel through a sebacic acid linker led to the formation of fluorescent nanoparticles. Dynamic light scattering (DLS) and photoluminescence spectroscopy were used for the identification and characterization of the fluorescent nanoparticles. The biological evaluation was determined in three human ovarian (KURAMOCHI, OVCAR3, OVSAHO) and three human breast (MCF7, SKBR 3, and MDA-MB231) cancer cell lines. In the case of cabazitaxel, the nanoparticles maintained the activity of the parent drug, at the low nanomolar range, while exhibiting high blue fluorescence. The internalization of the fluorescent NPs into cells was detected using immunofluorescence assay.

A wearable gloved sensor based on fluorescent Ag nanoparticles and europium complexes for visualized assessment of tetracycline in food samples

The abuse of tetracycline antibiotics leads to accumulating residues in the human body, seriously affecting human health. Establishing a sensitive, efficient, and reliable method for qualitative and quantitative detection of tetracycline (TC) is necessary. This study integrated silver nanoclusters and europium-based materials into the same nano-detection system to construct a visual and rapid TC sensor with rich fluorescence color changes. The nanosensor has the advantages of a low detection limit (10.5 nM), high detection sensitivity, fast response, and wide linear range (0-30 μM), which can meet the analysis requirements of different types of food samples. In addition, portable devices based on paper and gloves were designed. Through the smartphone's chromaticity acquisition and calculation analysis application (APP), the real-time rapid visual intelligent analysis of TC in the sample can be realized, which guides the intelligent application of multicolor fluorescent nanosensors.

Fluorescent detection of emerging virus based on nanoparticles: From synthesis to application

The spread of COVID-19 has caused huge economic losses and irreversible social impact. Therefore, to successfully prevent the spread of the virus and solve public health problems, it is urgent to develop detection methods with high sensitivity and accuracy. However, existing detection methods are time-consuming, rely on instruments, and require skilled operators, making rapid detection challenging to implement. Biosensors based on fluorescent nanoparticles have attracted interest in the field of detection because of their advantages, such as high sensitivity, low detection limit, and simple result readout. In this review, we systematically describe the synthesis, intrinsic advantages, and applications of organic dye-doped fluorescent nanoparticles, metal nanoclusters, up-conversion particles, quantum dots, carbon dots, and others for virus detection. Furthermore, future research initiatives are highlighted, including green production of fluorescent nanoparticles with high quantum yield, speedy signal reading by integrating with intelligent information, and error reduction by coupling with numerous fluorescent nanoparticles.

In vivo active-targeting fluorescence molecular imaging with adaptive background fluorescence subtraction

Using active tumor-targeting nanoparticles, fluorescence imaging can provide highly sensitive and specific tumor detection, and precisely guide radiation in translational radiotherapy study. However, the inevitable presence of non-specific nanoparticle uptake throughout the body can result in high levels of heterogeneous background fluorescence, which limits the detection sensitivity of fluorescence imaging and further complicates the early detection of small cancers. In this study, background fluorescence emanating from the baseline fluorophores was estimated from the distribution of excitation light transmitting through tissues, by using linear mean square error estimation. An adaptive masked-based background subtraction strategy was then implemented to selectively refine the background fluorescence subtraction. First, an in vivo experiment was performed on a mouse intratumorally injected with passively targeted fluorescent nanoparticles, to validate the reliability and robustness of the proposed method in a stringent situation wherein the target fluorescence was overlapped with the strong background. Then, we conducted in vivo studies on 10 mice which were inoculated with orthotopic breast tumors and intravenously injected with actively targeted fluorescent nanoparticles. Results demonstrated that active targeting combined with the proposed background subtraction method synergistically increased the accuracy of fluorescence molecular imaging, affording sensitive tumor detection.

Unraveling the Strong Fluorescence Enhancement of HPBI Molecules by ZIF-8 Colloidal Suspensions via Adsorption Analysis

Enhancing the fluorescence of organic dye by colloidal particles is one of the most promising routes to optimize fluorescence detection. However, in addition to metallic particles, which serve as the most frequently used particles and have been found to employ the plasmonic resonance to provide strong fluorescence enhancement, neither new types of colloidal particles nor new fluorescence mechanisms have been intensively explored in recent years. In this work, strongly enhanced fluorescence was observed when 2-(2-hydroxyphenyl)-1H-benzimidazole (HPBI) molecules were simply mixed with zeolitic imidazolate framework-8 (ZIF-8) colloidal suspensions. Moreover, the enhancement factor ΔI = I_HPBI+ZIF-8/I_HPBI does not increase accordingly with the increasing amount of HPBI. To find out how the strong fluorescence was triggered and affected by the amount of HPBI, multiple techniques were applied to analyze the adsorption behavior. By combining analytical ultracentrifugation with first-principles calculations, we proposed that HPBI molecules were adsorbed onto the surface of ZIF-8 particles coordinatively and electrostatically, depending on the concentration of HPBI molecules. The coordinative adsorption would result in a new kind of fluorescence emitter. The new fluorescence emitters tend to distribute on the outer surface of ZIF-8 particles periodically. The distance between each fluorescence emitter is fixed and much smaller than the wavelength of the excitation light. Thus, it can be concluded that collective spontaneous emission might be triggered.

Single-Cell Classification Based on Population Nucleus Size Combining Microwave Impedance Spectroscopy and Machine Learning

Many recent efforts in the diagnostic field address the accessibility of cancer diagnosis. Typical histological staining methods identify cancer cells visually by a larger nucleus with more condensed chromatin. Machine learning (ML) has been incorporated into image analysis for improving this process. Recently, impedance spectrometers have been shown to generate all-inclusive lab-on-a-chip platforms to detect nucleus abnormities. In this paper, a wideband electrical sensor and data analysis paradigm that can identify nuclear changes shows the realization of a single-cell microfluidic device to detect nuclei of altered sizes. To model cells of altered nucleus, Jurkat cells were treated to enlarge or shrink their nucleus followed by broadband sensing to obtain the S-parameters of single cells. The ability to deduce important frequencies associated with nucleus size is demonstrated and used to improve classification models in both binary and multiclass scenarios, despite a heterogeneous and overlapping cell population. The important frequency features match those predicted in a double-shell circuit model published in prior work, demonstrating a coherent new analytical technique for electrical data analysis. The electrical sensing platform assisted by ML with impressive accuracy of cell classification looks forward to a label-free and flexible approach to cancer diagnosis.

Targeting of phagolysosomes containing conidia of the fungus Aspergillus fumigatus with polymeric particles

Conidia of the airborne human-pathogenic fungus Aspergillus fumigatus are inhaled by humans. In the lung, they are phagocytosed by alveolar macrophages and intracellularly processed. In macrophages, however, conidia can interfere with the maturation of phagolysosomes to avoid their elimination. To investigate whether polymeric particles (PPs) can reach this intracellular pathogen in macrophages, we formulated dye-labeled PPs with a size allowing for their phagocytosis. PPs were efficiently taken up by RAW 264.7 macrophages and were found in phagolysosomes. When macrophages were infected with conidia prior to the addition of PPs, we found that they co-localized in the same phagolysosomes. Mechanistically, the fusion of phagolysosomes containing PPs with phagolysosomes containing conidia was observed. Increasing concentrations of PPs increased fusion events, resulting in 14% of phagolysosomes containing both conidia and PPs. We demonstrate that PPs can reach conidia-containing phagolysosomes, making these particles a promising carrier system for antimicrobial drugs to target intracellular pathogens. KEY POINTS: • Polymer particles of a size larger than 500 nm are internalized by macrophages and localized in phagolysosomes. • These particles can be delivered to Aspergillus fumigatus conidia-containing phagolysosomes of macrophages. • Enhanced phagolysosome fusion by the use of vacuolin1 can increase particle delivery.

Real scenario of metal ion sensor: is conjugated polymer helpful to detect hazardous metal ion

Metal ions from natural and anthropogenic sources cause pollution to society and the environment is major concern in the present scenario. The deposition and contamination of metal ions in soil and water affect the biogeochemical cycles. Thus, it threatens the everyday life of living and non-living organisms. Reviews on the detection of metal ions through several techniques (Analytical methods, electrochemical techniques, and sensors) and materials (Nanoparticles, carbon dots (quantum dots), polymers, chiral molecules, metal-organic framework, carbon nanotubes, etc.) are addressed separately in the present literature. This review reveals the advantages and disadvantages of the techniques and materials for metal ion sensing with crucial factors. Furthermore, it focus on the capability of conjugated polymers (CPs) as metal ion sensors able to detect/sense hazardous metal ions from environmental samples. Six different routes can synthesize this type of CPs to get specific properties and better metal ion detecting capability in vast research areas. The metal ion detection by CP is time-independent, simple, and low cost compared to other materials/techniques. This review outlines recent literature on the conjugated polymer for cation, anion, and dual ion sensors. Over the last half decades published articles on the conjugated polymer are discussed and compared.

Biomedical applications of metallic nanoparticles in cancer: Current status and future perspectives

The current advancements in nanotechnology are as an outcome of the development of engineered nanoparticles. Various metallic nanoparticles have been extensively explored for various biomedical applications. They attract lot of attention in biomedical field due to their significant inert nature, and nanoscale structures, with size similar to many biological molecules. Their intrinsic characteristics which include electronic, optical, physicochemical and, surface plasmon resonance, that can be changed by altering certain particle characteristics such as size, shape, environment, aspect ratio, ease of synthesis and functionalization properties have led to numerous applications in various fields of biomedicine. These include targeted drug delivery, sensing, photothermal and photodynamic therapy, imaging, as well as the modulation of two or three applications. The current article also discusses about the various properties of metallic nanoparticles and their applications in cancer imaging and therapeutics. The associated bottlenecks related to their clinical translation are also discussed.

DNA Templated Silver Nanoclusters for Bioanalytical Applications: A Review

Due to their unique programmability, biocompatibility, photostability and high fluorescent quantum yield, DNA templated silver nanoclusters (DNA Ag NCs) have attracted increasing attention for bioanalytical application. This review summarizes the recent developments in fluorescence properties of DNA templated Ag NCs, as well as their applications in bioanalysis. Finally, we herein discuss some current challenges in bioanalytical applications, to promote developments of DNA Ag NCs in biochemical analysis.

The effect of intermolecular electronic coupling on the exciton dynamics in perylene red nanoparticles

Understanding the transport mechanisms of electronic excitations in molecular systems is the basis for their application in light harvesting and opto-electronic devices. The exciton transfer properties depend pivotally on the intermolecular coupling and the latter on the supramolecular structure. In this work, organic nanoparticles of the perylene derivative Perylene Red are prepared with flash-precipitation under different conditions. We correlate their intermolecular couplings, optical spectra, quantum yields, emission lifetimes and their size and characterize their exciton dynamics upon excitation with ultrashort laser pulses by transient absorption spectroscopy. We find that the intermolecular coupling can be varied by changing the preparation conditions and thus the supramolecular structure. In contrast to the monomeric system, the generation of charge-transfer states is found after optical excitation of the nanoparticles. The time of the generation step is in the order of 100 ps and depends on the intermolecular coupling. The mobility of the originally excited excitons is determined from measurements with varying exciton density. To this end, we model the contribution of exciton-exciton annihilation to the exciton decay assuming three-dimensional incoherent diffusion. The extracted exciton diffusion constant of nanoparticles with stronger intermolecular coupling is found to be 0.17 nm2 ps-1 and thereby about ten times higher than in the particles with smaller coupling.

A spectrofluorometric analysis to evaluate transcutaneous biodistribution of fluorescent nanoparticulate gel formulations

The investigation of the absorption of drug delivery systems, designed for the transport of therapeutic molecules inside the body, could be relatively simplified by the fluorophore association and tracking by means of bio-imaging techniques (i.e., optical in vivo imaging or confocal and multiphoton microscopy). However, when a fluorescence signal comes out from the skin, its specific detection can be problematic. Skin high autofluorescence can hinder the observation of administered exogenous fluorophores conjugated to drug delivery systems, making it more challenging to detect their biodistribution. In the present study, we have developed a method based on the spectrofluorometric analysis of skin samples to discriminate the fluorescent signal coming from administered fluorescent molecules from the background. Moreover, we gave a semi-quantitative evaluation of the signal intensity. Thus, we distinguished two gel formulations loading the fluorophore rhodamine B (called GEL RHO and GEL SLN-RHO). The two formulations of gels, one of which containing solid lipid nanoparticles (GEL RHO-SLN), were administered on skin explants incubated in a bioreactor, and the penetration was evaluated at different time points (2 and 6 hours). Cryostatic sections of skin samples were observed with confocal laser scanning microscopy, and a spectrofluorometric analysis was performed. Significantly higher signal intensity in the samples administered with SLN-RHO GEL, with a preferential accumulation in the hair bulbs, was found. Reaching also the deeper layers of the hair shaft after 6 hours, the solid lipid nanoparticles thickened with polymer represent a suitable drug delivery system for transcutaneous administration.

Recent Advances in the Development and Applications of Conjugated Polymer dots

Conjugated polymer dots or semiconducting polymer nanoparticles (Pdots) are nanoparticles prepared based on organic polymers. Pdots have the advantages of lower cost, simple preparation process, good biocompatibility, excellent stability, easy...

Phytochemical profile and antiproliferative activities of acetone extracts of Asplenium polypodioides Blume. and A. dalhousiae Hook. in MDA-MB-231 breast cancer cells

The plants extracts are widely used in traditional medicines and hence considered a potential source for drug discovery. In this study, we assessed the phytochemical composition of Asplenium dalhousiae and Asplenium polypodioides in acetone extracts and checked its antiproliferative potential in MDA-MB-231 cells. We found that both plants are rich in phenolic and flavonoid compounds and are efficient in antioxidant activities. The total phenolic compounds in A. dalhousiae were 44.15 ± 1.38 µg/mg whereas in A. polypodioides were 27.73 ± 1.35 µg/mg. Total flavonoids in A. dalhousiae were 105.39 ± 2.92 µg/mg whereas in A. polypodioides were 101.56 ± 1.75 µg/mg. The ferric reducing power assay indicates 66.38 ± 2.6% reduction by A. dalhousiae whereas 78.43 ± 0.47% reduction by A. polypodioides. Similarly, the total antioxidant capacity of A. dalhousiae was found to be 59.95 ± 1.13 whereas for A. polypodioides the recorded value was 33.03 ± 1.67%. Using GCMS analysis, we identified 25 compounds in A. dalhousiae whereas 26 in A. polypodioides. Four of these compounds are common in both plants. The morphological study and MTT assay revealed that both plants have antiproliferative potential as both plants exerted significant effects on the shape of the MDA-MB-231 cells and inhibited cellular proliferation in time and dose dependent manner. We conclude that both Asplenium plants have potential anticancer compounds.

Dual Sensitivity─Potentiometric and Fluorimetric─Ion-Selective Membranes

Classical application of ion-selective membranes is limited to either electrochemical or optical experiments. Herein, the proposed ion-selective membrane system can be used in both modes; each of them offering competitive analytical parameters: high selectivity and linear dependence of the signal on logarithm of analyte concentration, high potential stability in potentiometric mode, or applicability for alkaline solutions in optical mode. Incorporation of analyte ions into the membrane results in potentiometric signals, as in a classical system. However, due to the presence of lipophilic positively charged ions, polymer backbones, full saturation of the membrane is prevented even for long contact time with solution. The presence of both positively charged and neutral forms of conducting polymers in the membrane results in high stability of potential readings in time. Optical signal generation is based on polythiophene particulates dispersed within the ion-selective membrane as the optical transducer. An increase of emission is observed with an increase of analyte contents in the sample.

Cubosome Based Ion-Selective Optodes-Toward Tunable Biocompatible Sensors

We report here on a new generation of optical ion-selective sensors benefiting from cubosomes or hexosomes-nanostructural lipid liquid phase. Cubosome as well as hexosome optodes offer biocompatibility, self-assembly preparation, high stability in solution, and unique, tunable analytical performance. The temperature trigger reversibly changes the lipid nanoparticle internal structure-changing analyte access to the bulk of the probe and ultimately affecting the response pattern. Thus, cubosome or hexosome optodes are highly promising alternatives to conventional polymeric based optical nanoprobes.

Recent advances in developing optical and electrochemical sensors for analysis of methamphetamine: A review

Recognition of misused stimulant drugs has always been a hot topic from a medical and judicial perspective. Methamphetamine (MAMP) is an addictive and illegal drug that profoundly affects the central nervous system. Like other illicit drugs, the detection of MAMP in biological and street samples is vital for several organizations such as forensic medicine, anti-drug headquarters and diagnostic clinics. By emerging nanotechnology and exploiting nanomaterials in sensing applications, a great deal of attention has been given to the design of analytical sensors in MAMP tracing. For the first time, this study has briefly reviewed all the optical and electrochemical sensors in MAMP detection from earlier so far. How various receptors with engineering nanomaterials allow developing novel approaches to measure MAMP have been studied. Fundamental concepts related to optical and electrochemical recognition assays in which nanomaterials have been used and relevant MAMP sensing applications have been comprehensively covered. Challenges, opportunities and future outlooks of this field have also been discussed at the end.

Stimuli-responsive polymer-based systems for diagnostic applications

Stimuli-responsive polymers exhibit properties that make them ideal candidates for biosensing and molecular diagnostics. Through rational design of polymer composition combined with new polymer functionalization and synthetic strategies, polymers with myriad responsivities, e.g., responses to temperature, pH, biomolecules, CO2, light, and electricity can be achieved. When these polymers are specifically designed to respond to biomarkers, stimuli-responsive devices/probes, capable of recognizing and transducing analyte signals, can be used to diagnose and treat disease. In this review, we highlight recent state-of-the-art examples of stimuli-responsive polymer-based systems for biosensing and bioimaging.

A "turn-on" and proximity ligation assay dependent DNA tweezer for one-step amplified fluorescent detection of DNA

A "turn-on" and proximity ligation assay dependent DNA tweezer was proposed for one-step amplified fluorescent detection of DNA. Target DNA can anneal with capture probe to form an entire long sequence. The formed long sequence can circularly open the hairpin, resulting the "turn-on" of DNA tweezers. A good linear relationship was shown from 40 pM to 20 nM with limit of detection of 10 pM. In addition, it has been successfully utilized to analysis DNA in human serum, representing a great and practical application future.

Photoluminescence-based immunochemical methods for determination of C-reactive protein and procalcitonin

Modern, sensitive, rapid, and selective analytical methods for the detection of inflammatory markers are a crucial tool for the assessment of inflammation state, efficacy of medical intervention, and the prediction of future diseases. Their development requires understanding of current state for point-of-care testing of inflammatory markers and identification of their crucial drawbacks. This review summarizes the progress in the application of luminescent labels for immunoassays. The luminescent labels became more popular in the latest decade due to their high sensitivity, selectivity, and robustness. This review presents a constructive analysis of different luminescent labels such as fluorescent organic dyes, quantum dots, long-lived emissive nanoparticles, and up-converting nanocrystals, as well as a range of the strategies for inflammatory markers determination. The advantages and disadvantages of all classes of luminescent labels are demonstrated, and the strategies of labels modification for their improvement are discussed. The current approaches for the creation of luminescent probes and robust assays are also highlighted.

Peptide-Engineered Fluorescent Nanomaterials: Structure Design, Function Tailoring, and Biomedical Applications

Fluorescent nanomaterials have exhibited promising applications in biomedical and tissue engineering fields. To improve the properties and expand bioapplications of fluorescent nanomaterials, various functionalization and biomodification strategies have been utilized to engineer the structure and function of fluorescent nanomaterials. Due to their high biocompatibility, satisfied bioactivity, unique biomimetic function, easy structural tailoring, and controlled self-assembly ability, supramolecular peptides are widely used as versatile modification agents and nanoscale building blocks for engineering fluorescent nanomaterials. In this work, recent advance in the synthesis, structure, function, and biomedical applications of peptide-engineered fluorescent nanomaterials is presented. Firstly, the types of different fluorescent nanomaterials are introduced. Then, potential strategies for the preparation of peptide-engineered fluorescent nanomaterials via templated synthesis, bioinspired conjugation, and peptide assembly-assisted synthesis are discussed. After that, the unique structure and functions through the peptide conjugation with fluorescent nanomaterials are demonstrated. Finally, the biomedical applications of peptide-engineered fluorescent nanomaterials in bioimaging, disease diagnostics and therapy, drug delivery, tissue engineering, antimicrobial test, and biosensing are presented and discussed in detail. It is helpful for readers to understand the peptide-based conjugation and bioinspired synthesis of fluorescent nanomaterials, and to design and synthesize novel hybrid bionanomaterials with special structures and improved functions for advanced applications.

Visualization of O2/ATP cross-talk in living cells with a smart fluorescent nanoprobe

Herein, we propose a dual-responsive fluorescent nanoprobe to visualize the cross-talk between O2 and adenosine triphosphate (ATP) in living cells. We hope it will be a helpful tool for the further understanding of cellular metabolism and further facilitating risk warning in the process of adaptation to consistent environmental pressures in premalignant lesions.

Recent advances in semiconducting polymer dots as optical probes for biosensing

This review mainly summarized the recent results that used bright polymer dots (Pdots) for the detection of different analytes such as reactive oxygen species (ROS), metal ions, pH values, and a variety of biomolecules.

Enhancing upconversion emissions and temperature sensing properties by incorporating Mn2+ for KLu2F7:Yb3+/Er3+ nanocrystals based on thermally and non-thermally coupled levels

Pure phase KLu₂F₇:Yb³⁺/Er³⁺/Mn²⁺ nanocrystals were obtained for which the temperature sensitivity reached up to 45.11 × 10⁻³ K⁻¹ employing non-thermally coupled levels.

Variably Sized and Multi-Colored Silica-Nanoparticles Characterized by Fluorescence Correlation Methods for Cellular Dynamics

Controlling the uptake of nanoparticles into cells so as to balance therapeutic effects with toxicity is an essential unsolved problem in the development of nanomedicine technologies. From this point of view, it is useful to use standard nanoparticles to quantitatively evaluate the physical properties of the nanoparticles in solution and in cells, and to analyze the intracellular dynamic motion and distribution of these nanoparticles at a single-particle level. In this study, standard nanoparticles are developed based on a variant silica-based nanoparticle incorporating fluorescein isothiocyanate (FITC) or/and rhodamine B isothiocyanate (RITC) with a variety of accessible diameters and a matching fluorescent cobalt ferrite core-shell structure (Fe₂O₄/SiO₂). The physical and optical properties of the nanoparticles in vitro are fully evaluated with the complementary methods of dynamic light scattering, electron microscopy, and two fluorescence correlation methods. In addition, cell uptake of dual-colored and core/shell nanoparticles via endocytosis in live HeLa cells is detected by fluorescence correlation spectroscopy and electron microscopy, indicating the suitability of the nanoparticles as standards for further studies of intracellular dynamics with multi-modal methods.

Fluorescent Nanoparticles for Targeted Tumor Imaging and DNA Tracking Gene Delivery In Vitro/In Vivo

Fluorescence detection is desirable to track the gene transfer process in order to explain the mechanism. Here, a fluorescent nanoparticle, diketopyrrolopyrrole-based liposome (DPL), was prepared for DNA delivery and tumor imaging in vitro and in vivo. The process to deliver DNA into cells was detected in real time by DPL according to the fluorescent property. The transfection efficacies (TEs) for luciferase and enhanced green fluorescent protein (EGFP) analysis of DPL were 1.5 times those of the commercial transfection agent Lipo 2000. Importantly, the DPL/DNA system has high EGFP TE in vivo with tumor targeting ability. This work provided an effective strategy for monitoring transfection processes.