Biomimetic two-dimensional nanozymes: synthesis, hybridization, functional tailoring, and biosensor applications.

Biological enzymes play important roles in mediating the biological reactions in vitro and in vivo due to their high catalytic activity, strong bioactivity, and high specificity; however, they have also some disadvantages such as high cost, low environmental stability, weak reusability, and difficult production. To overcome these shortcomings, functional nanomaterials including metallic nanoparticles, single atoms, metal oxides, alloys, and others have been utilized as nanozymes to mimic the properties and functions of natural enzymes. Due to the development of the synthesis and applications of two-dimensional (2D) materials, 2D nanomaterials have shown high potential to be used as novel nanozymes in biosensing, bioimaging, therapy, logic gates, and environmental remediation due to their unique physical, chemical, biological, and electronic properties. In this work, we summarize recent advances in the preparation and functionalization, as well as biosensor and immunoassay applications of various 2D material-based nanozymes. To achieve this aim, first we demonstrate the preparation strategies of 2D nanozymes such as chemical reduction, templated synthesis, chemical exfoliation, calcination, electrochemical deposition, hydrothermal synthesis, and many others. Meanwhile, the structure and properties of the 2D nanozymes prepared by conjugating 2D materials with nanoparticles, metal oxides, biomolecules, polymers, ions, and 2D heteromaterials are introduced and discussed in detail. Then, the applications of the prepared 2D nanozymes in colorimetric, electrochemical, fluorescent, and electrochemiluminescent sensors are demonstrated.

Novel and label-free colorimetric detection of radon using AuNPs and lead(II)-induced GR5 DNAzyme-based amplification strategy.

Radioactive radon decays into a stable daughter product, 210Pb, which was used as the detection target to determine the radon radiation dose in a new technique. Pb2+ triggers DNAzyme to cleave a molecular beacon (MB), resulting in the stem-loop structure opening and forming two single DNA strands (ssDNA). The ssDNA binds to unmodified gold nanoparticles and effectively prevents their aggregation in a salt solution. The detached enzyme strands continue to complement the remaining MB to amplify the response signal. The method proposed in this study exhibited a good linear relationship for Pb2+ and radon concentrations in the range of 6.22 × 102-1.02 × 105 Bq h/m3 with a detection limit of 186.48 Bq h/m3 using an ultraviolet-visible spectrometer. In practical applications, this sensitive method can avoid radioactive damage in field testing, and the detection limit meets the national standard in China. Importantly, this simple, highly sensitive strategy uses simple equipment and has a strong anti-interference ability. Graphical abstract.

A review of chemical 'spot' tests: A presumptive illicit drug identification technique.

Chemical 'spot' tests are a presumptive illicit drug identification technique commonly used by law enforcement, border security personnel, and forensic laboratories. The simplicity, low cost, and rapid results afforded by these tests make them particularly attractive for presumptive identification globally. In this paper, we review the development of these long-established methods and discuss color test recommendations and guidelines. A search of the scientific literature revealed the chemical reactions occurring in many color tests are either not actively investigated or reported as unknown. Today, color tests face many challenges, from the appearance of new psychoactive substances to concerns regarding selectivity, sensitivity, and safety. Advances in technology have seen color test reagents used in digital image color analysis, solid sensors, and microfluidic devices for illicit drug detection. This summarizes current research and suggests the future of presumptive color testing.

Reply to Letter to the Editor by Griffiths et al. commenting on Evans & Allen: Letter to the Editor concerning «A systematic review of controlled trials on visual stress using intuitive overlays or colorimeter» / Respuesta a la carta al editor de Griffiths et al., como comentario al documento de Evans & Allen: Carta al Editor en relación a «Revisión sistemática de ensayos controlados sobre estrés visual utilizando filtros intuitivos o colorímetro»

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A new colorimetric DPPH• scavenging activity method with no need for a spectrophotometer applied on synthetic and natural antioxidants and medicinal herbs.

2,2-Diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging, the most commonly used antioxidant method with more than seventeen thousand articles cited, is very practical; however, as with most assays, it has the major disadvantage of dependence on a spectrophotometer. To overcome this drawback, the colorimetric determination of the antioxidant activity using a scanner and freely available Image J software was developed. In this new method, the mixtures of solutions of DPPH• and standard antioxidants or extracts of common medicinal herbs were dropped onto TLC plates, after an incubation period. The spot images were evaluated with Image J software to determine CSC50 values, the sample concentrations providing 50% colour reduction, which were very similar with the SC50 values obtained with spectrophotometric method. The advantages of the new method are the use of lower amounts of reagents and solvents, no need for costly spectrophotometers, and thus significantly lowered costs, and convenient implementation in any environment and situation.

A novel colorimetric PCR-based biosensor for detection and quantification of hepatitis B virus.

Hepatitis B virus (HBV) can cause viral infection that attacks the liver and it is a major global health problem that put people at a high risk of death from cirrhosis of the liver and liver cancer. HBV has infected one third of the worldwide population, and 350 million people suffer from chronic HBV infection. For these reasons, development of an accurate, sensitive and expedient detection method for diagnosing, monitoring and assessing therapeutic response of HBV is very necessary and urgent for public health and disease control. Here we report a new strategy for detection of viral load quantitation of HBV based on colorimetric polymerase chain reaction (PCR) with DNAzyme-containing probe. The special DNAzyme adopting a G-quadruplex structure exhibited peroxidase-like activity in the presence of hemin to report colorimetric signal. This method has shown a broad range of linearity and high sensitivity. This study builds important foundation to achieve the specific and accurate detection level of HBV DNA with a low-cost and effective method in helping diagnosing, preventing and protecting human health form HBV generally all over the world and especially in developing countries.

Nanoparticle-based immunoassays in the biomedical field.

Recent research has looked to develop innovative, powerful and novel biofunctionalized nanoparticles, controlling and tailoring their properties in a very predictable manner to meet the needs of clinic immunoassays in the biomedical field. This minireview briefly summarizes recent advances covering the last 3 years, exploiting nanoparticle-based electrochemical, optical, mass-sensitive, colorimetric and immunodipstick assays. The enormous signal enhancement associated with the use of nanoparticles and formation of nanoparticle-antibody-antigen assemblies provide the basis for sensitive detection of disease-related proteins or biomarkers. Rather than being exhaustive, this minireview focuses on selected examples to illustrate novel concepts and promising applications. Finally, a small amount of speculation of possible future developments in nanoparticle-based immunoassays is provided.

Interphase chromosome-specific multicolor banding (ICS-MCB): a new tool for analysis of interphase chromosomes in their integrity.

Biomedical research of interphase chromosomes in their integrity is hindered by technical limitations. We introduce a technology using microdissection-based engineering of DNA probes and fluorescence multicolor chromosome banding that allows studying interphase chromosome organization, numbers and rearrangements in somatic cells.

Locating basic Spanish colour categories in CIE L*u*v* space: Identification, lightness segregation and correspondence with English equivalents

Se realizaron cinco experimentos para identificar las categorías cromáticas básicas (CCB) del español y ubicarlas en el espacio CIE L*u*v*. Empleando una tarea de listas elicitadas y otra de denominación monolexémica libre, se confirmó la existencia de 11 CCB. Mediante una tarea de estimación de sinonimia, se concluyó que, en español, se emplean 2 términos sinónimos (morado y violeta) para denominar una categoría equivalente a la inglesa purple. Tres experimentos proporcionaron información acerca de la localización colorimétrica de las 11 CCB del español. Dos emplearon tareas de denominación monolexémica (libre y restringida) y el tercero requirió la señalización de prototipos y de buenos ejemplares. Se observó que las CCB del español y del inglés son esencialmente equivalentes en número y delimitación colorimétrica, por lo puede considerarse que nuestro trabajo extiende y complementa la investigación previa (sobre CCB inglesas) en lo referente a la localización de las categorías acromáticas en el espacio de color, los vínculos entre categorías cromáticas y acromáticas (ni rojo ni naranja tienen vínculos directos con las categorías acromáticas), y la dependencia de la claridad que muestra el uso de las CCB. Por último, destaca la existencia de 2 categorías próximas a ser básicas: beige y granate(AU)

Five experiments were performed to identify the basic Spanish colour categories (BCCs) and to locate them in the CIE L*u*v* space. The existence of 11 BCCs was confirmed using an elicited list task and a free monolexemic naming task. From the results provided by a synonymicity estimation task, it was concluded that, in Spanish, 2 synonymous terms (morado and violeta) are used to name a category equivalent to the English category purple. Three experiments provided information about the colourimetric localization of the 11 Spanish BCCs. Two experiments used monolexemic naming tasks (free and restricted) and a third required the free signalling of prototypes and good exemplars. It was observed that Spanish and British BCCs are essentially equivalents in number and colourimetric delimitation and, therefore, our work can be considered to extend and complement previous research (on English BCCs) insofar as achromatic categories in colour space localization, the links between chromatic and achromatic categories (red and orange have no direct links with achromatic categories), and the dependence of the use of BCCs on lightness are concerned. Lastly, our results indicate the existence of 2 categories that are nearly basic: beige and garnet(AU)

Spectrophotometric and colorimetric determination of protein concentration.

This unit describes spectrophotometric and colorimetric methods for measuring the concentration of a sample protein in solution. Absorbance measurement at 280 nm is used to calculate protein concentration by comparison with a standard curve or published absorptivity values for that protein. An alternate protocol uses absorbance at 205 nm to calculate the protein concentration. Both methods can be used to quantitate total protein in crude lysates and purified or partially purified protein. Use of a spectrofluorometer or a filter fluorometer to measure the intrinsic fluorescence emission of a sample solution is also described. The measurement is compared with the emissions from standard solutions to determine the concentration of purified protein. The Bradford colorimetric method, based upon binding of the dye Coomassie brilliant blue to an unknown protein, is also presented, as is the Lowry method, which measures colorimetric reaction of tyrosyl residues in an unknown.

Ensayo colorimétrico de hibridación en microplacas para la detección de Mycobacterium leprae 16s rRNA en muestras clínicas

Se ha desarrollado un ensayo colorimétrico de hibridación en microplacas para simplificar la detección de Mycobacterium leprae en muestras clínicas. La técnica detecta los productos amplificados por un ensayo muy sensible RT-PCR con diana sobre una secuencia especie-específica del rRNA 16S bacteriano. El test detectó hasta 10 bacilos aislados de los nódulos linfáticos de ratones desnudos infectados o biopsias cutáneas humanas. La sensibilidad para el diagnóstico en nuestras clínicas se evaluó en 58 biopsias cutáneas de 58 pacientes de lepra sin tratar. El ensayo detectó amplificados RT-PCR de M. leprae en el 100 por ciento de las biopsias de pacientes con lepra multibacilar y el 80 por ciento de biopsias de pacientes paucibacilares, con una sensibilidad total de 91.3 por ciento. El test resultó ser muy específico ya que no se detectaron amplificaciones en las biopsias de pacientes normales o afectados de otras enfermedades distintas a la lepra. La variante colorimétrica es más rápido, sensible y simplifica la detección de los amplificados RT-PCR comparado con el análisis por Southern blot. Puede ser útil para el diagnóstico de los casos difíciles de lepra y como el RNA se degrada rápidamente después de la inactivación celular siendo útil para la evaluación de la respuesta al tratamiento y distinción de recidivas de reacción (AU)

Frederic Ives Medal paper. History and current status of a physiologically based system of photometry and colorimetry.

The CIE chromaticity diagram, which has been in common use for more than 60 years, disguises essential relations among cone excitations that become transparent in a system developed with D. I. A. MacLeod and initially proposed by the author to the CIE in 1979. This proposal led to the formation of a CIE committee to consider an ideal version of the system, to be employed either as a supplement to, or an alternative for, the 1931 "standard observer". After 15 years, the task remains unfinished. The history of debate within the original committee and that of its successor (which is still active today) is briefly reviewed. Among cone fundamentals that might be chosen, a set derived and published by Stockman, MacLeod, and Johnson [J. Opt. Soc. Am. A 10, 2491 (1993)] is favored here, and some of the advantages for displaying visual data in a system based on these fundamentals are illustrated.