Carbon "quantum" dots for bioapplications

Detection of GSH with a dual-mode biosensor based on carbon quantum dots prepared from dragon fruit peel and the T-Hg(II)-T mismatch

Glutathione (GSH) is commonly used as a diagnostic biomarker for many diseases. In this study, based on carbon quantum dots prepared from dragon fruit peel (D-CQDs) and the T-Hg(II)-T mismatch, a dual-mode biosensor was developed for the detection of GSH. This system consists of two single-stranded DNA (ssDNA). DNA1 was the T-rich sequence; DNA2 was attached to streptavidin-coated magnetic beads and consisted of T-rich and G-rich fragments. Due to the presence of Hg(II), the T-Hg(II)-T mismatch was formed between T-rich fragments of two ssDNA. In the presence of GSH, Hg(II) detached from dsDNA and bound with GSH to form a new complex. The G-rich fragment assembled with the hemin shed from D-CQDs to form the G-quadruplex/hemin complex. At this time, in fluorescence mode, the fluorescence of D-CQDs quenched by hemin could be restored. In colorimetric mode, after the magnetic beads separate, a visual signal could be produced by catalyzing the oxidation of ABTS using the peroxide-like activity of the G-quadruplex/hemin complex. This biosensor in both fluorescence mode and colorimetric mode had excellent selectivity and sensitivity, and the limit of detection was 0.089 µM and 0.26 µM for GSH, respectively. Moreover, the proposed dual-mode biosensor had good application prospects for detection of GSH.

Research Progress in Nanoparticle Inhibitors for Crude Oil Asphaltene Deposition

Currently, the alteration of external factors during crude oil extraction easily disrupts the thermodynamic equilibrium of asphaltene, resulting in the continuous flocculation and deposition of asphaltene molecules in crude oil. This accumulation within the pores of reservoir rocks obstructs the pore throat, hindering the efficient extraction of oil and gas, and consequently, affecting the recovery of oil and gas resources. Therefore, it is crucial to investigate the principles of asphaltene deposition inhibition and the synthesis of asphaltene inhibitors. In recent years, the development of nanotechnology has garnered significant attention due to its unique surface and volume effects. Nanoparticles possess a large specific surface area, high adsorption capacity, and excellent suspension and catalytic abilities, exhibiting unparalleled advantages compared with traditional organic asphaltene inhibitors, such as sodium dodecyl benzene sulfonate and salicylic acid. At present, there are three primary types of nanoparticle inhibitors: metal oxide nanoparticles, organic nanoparticles, and inorganic nonmetal nanoparticles. This paper reviews the recent advancements and application challenges of nanoparticle asphaltene deposition inhibition technology based on the mechanism of asphaltene deposition and nano-inhibitors. The aim was to provide insights for ongoing research in this field and to identify potential future research directions.

Aptamer SERS and RRS determination of trace lead ions using nitrogen-doped carbon dot to catalyze the new nano-gold reaction

Nitrogen-doped carbon dots (CDN) were prepared by microwave hydrothermal method using ammonium citrate (AC) and ethylenediaminetetraacetic acid (EDTA) as precursor. It was characterized by transmission electron microscopy (TEM) and infrared spectroscopy (IR). The CDN was found to catalyze the reduction of HAuCl4 to produce gold nanoparticles (AuNP), among which fructose was an effective reducing agent. Using malachite green (MG) as a molecular probe, the surface enhanced Raman scattering (SERS) intensity at 1617 cm-1 and the resonance Rayleigh scattering (RRS) intensity at 375 nm increased linearly with increasing CDN concentration, respectively. The catalytic activity of CDN is inhibited because the aptamer (Apt) can be adsorbed on the surface of the catalyst CDN. The aptamer (Apt)-Pb2+ reaction and CDN-Apt adsorbing reaction were competitive reaction. When there is Pb2+ that binds more tightly to Apt, Apt is desorbed, and the catalytic ability of CDN is restored. Accordingly, an Apt-mediated nanocatalytic amplification SERS/RRS platform for quantitative detection of lead ions was constructed. For the SERS method, the linear range was 0.5-120 nmol/L with DL of 0.11 nmol/L. For the RRS method, the Pb2+ concentration was linear in the range of 50-400 nmol/L with the RRS intensity, and the DL was 15.32 nmol/L. The analysis platform uses CDN catalyzed nanoreactions to generate AuNP products with SERS activity as a substrate, thus overcoming the shortcomings of Pb2+ without scattering activity, and realizing the possibility of SERS and RRS detection of metal ions. It was used for the determination of Pb2+ in real samples with relative standard deviations were 0.94-2.71 % and recovery was 99.00-103.70 %, respectively. In addition, the mechanism of CDN nanoenzyme heterogeneous catalysis of nano-gold reactions was discussed.

A Photoelectrochemical Sensor Based on DNA Bio-Dots-Induced Aggregation of AuNPs for Methionine Detection

Based on DNA bio-dots-induced aggregation of gold nanoparticles (AuNPs), a methionine (Met) photoelectrochemical (PEC) sensor with CS-GSH-CuNCs/TiO2 NPs as the photoelectric conversion element and AuNPs as the specific recognition element was constructed. First, a TiO2 NPs/ITO electrode and CS-GSH-CuNCs were prepared, and then the CS-GSH-CuNCs/TiO2 NPs/ITO photosensitive electrode was obtained by self-assembly. Next, DNA bio-dots were modified to the upper surface of the electrode using a coupling reaction to assemble the DNA bio-dots/CS-GSH-CuNCs/TiO2 NPs electrode. Amino-rich DNA bio-dots were used to induce the aggregation of AuNPs on the electrode surface via Au-N interactions and prepare the AuNPs/DNA bio-dots/CS-GSH-CuNCs/TiO2 NPs electrode. Due to the fluorescence resonance energy transfer (FRET) between CS-GSH-CuNCs and AuNPs, the complexation chance of electron-hole (e--h+) pair in CS-GSH-CuNCs increased, which, in turn, led to a decrease in photocurrent intensity. When Met was present, AuNPs aggregated on the electrode surface were shed and bound to Met since the Au-S interaction is stronger than the Au-N interaction, resulting in the recovery of the photocurrent signal. Under optimal conditions, the photocurrent intensity of the PEC sensor showed good linearity with the logarithm of Met concentration in the range of 25.0 nmol/L-10.0 μmol/L with the limit of detection (LOD) of 5.1 nmol/L (S/N = 3, n = 10).

Bibliometric analysis of aptamer-conjugated nanoparticles for diagnosis in the last two decades

Objective.Aptamer-conjugated nanoparticles for diagnosis have recently gained increasing attention. Here, we performed a bibliometric analysis to provide an overview of this field over the past two decades.Methods. The terms 'aptamer, nanoparticles and diagnosis' were used to search for relevant original articles published in English from 2003 to 2022 in the Web of Science database. VOSviewer and CiteSpace software were employed to analyze the development process, knowledge structure, research hotspots, and potential trends in the field of aptamer-conjugated nanoparticles for diagnosis.Results. A total of 1076 original articles were retrieved, with a rapid increase in the annual output and citation. The journal 'Biosensors and Bioelectronics' has contributed the most in this field, and the most influential researcher, institution and country were Weihong Tan, the Chinese Academy of Sciences, China, respectively. Gold nanoparticles and quantum dots were the most used, but in the past three years, research hotspots focused on carbon dots and graphene quantum dots. Diagnostic directions primarily focused on cancer. The most used strategy was label-free electrochemical detection, but in the past two years, colorimetric analysis and fluorescence imaging emerged as hot topics.Conclusion.The bibliometric analysis reveals a rapid increase in the research on aptamer-conjugated nanoparticles for diagnosis, major contributors at the levels of journals, authors, institutions, and countries, and research preferences in diagnostic objects, nanoparticle types, and detection methods, as well as the evolution of research hotspots and future trends.

Development of a biomimetic DNA delivery system by encapsulating polyethyleneimine functionalized silicon quantum dots with cell membranes

Quantum dots (QDs) are renowned for their remarkable optoelectronic properties, making them suitable for applications such as bioimaging and optoelectronics. However, their use in gene delivery has been restricted due to the low DNA loading capacity. This study aimed to develop a biomimetic DNA delivery system by encapsulating polyethyleneimine (PEI) functionalized silicon QDs (SiQDs) with cell membranes and evaluate its potential as a gene vector in vitro. To achieve this, hydrophilic dispersed silicon QDs (PQDs) were prepared through a one-pot hydrothermal reaction of PEI and 3-Aminopropyltrimethoxysilane (APTMS). Subsequently, red blood cell membrane (RBCM) encapsulated biomimetic QDs (CM-PQDs) was obtained through the extrusion method. The CM-PQDs exhibited higher DNA loading capacity and better stability than naked SiQDs. The CM-PQDs/DNA complex was effectively taken up by cells, as observed through the fluorescence characteristics of QDs themselves. Both CM-P10QDs (prepared with PEI10k) and CM-P25QDs (prepared with PEI25k) could deliver DNA into cells and express the reporter protein successfully. CM-P25QDs showed a higher transfection efficiency of 77.32% in 293 T cells and 47.11% in HeLa cells than SiQDs and CM-P10QDs. The results also indicated that cell membrane encapsulation could effectively reduce the cytotoxicity of SiQDs further. Therefore, the study concludes that CM-PQDs have the potential to serve as a safe and traceable biomimetic gene delivery system.

Zero-Dimensional Carbon Nanomaterials for Fluorescent Sensing and Imaging

Advances in nanotechnology and nanomaterials have attracted considerable interest and play key roles in scientific innovations in diverse fields. In particular, increased attention has been focused on carbon-based nanomaterials exhibiting diverse extended structures and unique properties. Among these materials, zero-dimensional structures, including fullerenes, carbon nano-onions, carbon nanodiamonds, and carbon dots, possess excellent bioaffinities and superior fluorescence properties that make these structures suitable for application to environmental and biological sensing, imaging, and therapeutics. This review provides a systematic overview of the classification and structural properties, design principles and preparation methods, and optical properties and sensing applications of zero-dimensional carbon nanomaterials. Recent interesting breakthroughs in the sensitive and selective sensing and imaging of heavy metal pollutants, hazardous substances, and bioactive molecules as well as applications in information encryption, super-resolution and photoacoustic imaging, and phototherapy and nanomedicine delivery are the main focus of this review. Finally, future challenges and prospects of these materials are highlighted and envisaged. This review presents a comprehensive basis and directions for designing, developing, and applying fascinating fluorescent sensors fabricated based on zero-dimensional carbon nanomaterials for specific requirements in numerous research fields.

Recent Advancements in Metal and Non-Metal Mixed-Doped Carbon Quantum Dots: Synthesis and Emerging Potential Applications

In nanotechnology, the synthesis of carbon quantum dots (CQDs) by mixed doping with metals and non-metals has emerged as an appealing path of investigation. This review offers comprehensive insights into the synthesis, properties, and emerging applications of mixed-doped CQDs, underlining their potential for revolutionary advancements in chemical sensing, biosensing, bioimaging, and, thereby, contributing to advancements in diagnostics, therapeutics, and the under standing of complex biological processes. This synergistic combination enhances their sensitivity and selectivity towards specific chemical analytes. The resulting CQDs exhibit remarkable fluorescence properties that can be involved in precise chemical sensing applications. These metal-modified CQDs show their ability in the selective and sensitive detection from Hg to Fe and Mn ions. By influencing their exceptional fluorescence properties, they enable precise detection and monitoring of biomolecules, such as uric acid, cholesterol, and many antibiotics. Moreover, when it comes to bioimaging, these doped CQDs show unique behavior towards detecting cell lines. Their ability to emit light across a wide spectrum enables high-resolution imaging with minimal background noise. We uncover their potential in visualizing different cancer cell lines, offering valuable insights into cancer research and diagnostics. In conclusion, the synthesis of mixed-doped CQDs opens the way for revolutionary advancements in chemical sensing, biosensing, and bioimaging. As we investigate deeper into this field, we unlock new possibilities for diagnostics, therapeutics, and understanding complex biological processes.

Carbon Dots: Classically Defined versus Organic Hybrids on Shared Properties, Divergences, and Myths

Carbon dots are defined as small carbon nanoparticles with effective surface passivation via organic functionalization. The definition is literally a description of what carbon dots are originally found for the functionalized carbon nanoparticles displaying bright and colorful fluorescence emissions, mirroring those from similarly functionalized defects in carbon nanotubes. In literature more popular than classical carbon dots are the diverse variety of dot samples from "one-pot" carbonization of organic precursors. On the two different kinds of samples from the different synthetic approaches, namely, the classical carbon dots versus those from the carbonization method, highlighted in this article are their shared properties and apparent divergences, including also explorations of the relevant sample structural and mechanistic origins for the shared properties and divergences. Echoing the growing evidence and concerns in the carbon dots research community on the major presence of organic molecular dyes/chromophores in carbonization produced dot samples, demonstrated and discussed in this article are some representative cases of dominating spectroscopic interferences due to the organic dye contamination that have led to unfound claims and erroneous conclusions. Mitigation strategies to address the contamination issues, including especially the use of more vigorous processing conditions in the carbonization synthesis, are proposed and justified.

Stable Carbon Dots from Microwave-Heated Carbon Nanoparticles Generating Organic Radicals for In Situ Additions

Carbon dots (CDots) are small carbon nanoparticles with effective surface passivation by organic functionalization. In the reported work, the surface functionalization of preexisting small carbon nanoparticles with N-ethylcarbazole (NEC) was achieved by the NEC radical addition. Due to the major difference in microwave absorption between the carbon nanoparticles and organic species such as NEC, the nanoparticles could be selectively heated via microwave irradiation to enable the hydrogen abstraction in NEC to generate NEC radicals, followed by in situ additions of the radicals to the nanoparticles. The resulting NEC-CDots were characterized by microscopy and spectroscopy techniques including quantitative proton and 13C NMR methods. The optical spectroscopic properties of the dot sample were found to be largely the same as those of CDots from other organic functionalization schemes. The high structural stability of NEC-CDots benefiting from the radical addition functionalization is highlighted and discussed.