Chemiluminescence microfluidic system of gold nanoparticles enhanced luminol-silver nitrate for the determination of vitamin B12

Microfluidic assessment of nutritional biomarkers: Concepts, approaches and advances

Among various approaches to understand the health status of an individual, nutritional biomarkers can provide valuable information, particularly in terms of deficiencies, if any, and their severity. Commonly, the approach revolves around molecular sciences, and the information gained can support prognosis, diagnosis, remediation, and impact assessment of therapies. Microfluidic platforms can offer benefits of low sample and reagent requirements, low cost, high precision, and lower detection limits, with simplicity in handling and the provision for complete automation and integration with information and communication technologies (ICTs). While several advances are being made, this work details the underlying concepts, with emphasis on different point-of-care devices for the analysis of macro and micronutrient biomarkers. In addition, the scope of using different wearable microfluidic sensors for real-time and noninvasive determination of biomarkers is detailed. While several challenges remain, a strong focus is given on recent advances, presenting the state-of-the-art of this field. With more such biomarkers being discovered and commercialization-driven research, trends indicate the wide prospects of this advancing field in supporting clinicians, food technologists, nutritionists, and others.

Current Nanocarrier Strategies Improve Vitamin B12 Pharmacokinetics, Ameliorate Patients' Lives, and Reduce Costs

Vitamin B12 (VitB12) is a naturally occurring compound produced by microorganisms and an essential nutrient for humans. Several papers highlight the role of VitB12 deficiency in bone and heart health, depression, memory performance, fertility, embryo development, and cancer, while VitB12 treatment is crucial for survival in inborn errors of VitB12 metabolism. VitB12 is administrated through intramuscular injection, thus impacting the patients’ lifestyle, although it is known that oral administration may meet the specific requirement even in the case of malabsorption. Furthermore, the high-dose injection of VitB12 does not ensure a constant dosage, while the oral route allows only 1.2% of the vitamin to be absorbed in human beings. Nanocarriers are promising nanotechnology that can enable therapies to be improved, reducing side effects. Today, nanocarrier strategies applied at VitB12 delivery are at the initial phase and aim to simplify administration, reduce costs, improve pharmacokinetics, and ameliorate the quality of patients’ lives. The safety of nanotechnologies is still under investigation and few treatments involving nanocarriers have been approved, so far. Here, we highlight the role of VitB12 in human metabolism and diseases, and the issues linked to its molecule properties, and discuss how nanocarriers can improve the therapy and supplementation of the vitamin and reduce possible side effects and limits.

Rapid evaluation of oxygen vacancies-enhanced photogeneration of the superoxide radical in nano-TiO2 suspensions

Reactive oxygen species (ROS) play an important role in the photocatalytic degradation of pollutants and are closely related to the surface defects of a semiconductor. However, the characterization of surface defects is very complex and a deeper understanding of them remains a great challenge. In this work, a series of nano-TiO2 was synthesized and their optical properties due to surface defects were studied. The results showed that the surface oxygen vacancies on nano-TiO2 can induce chemiluminescence (CL) by luminol. The greater the number of surface oxygen vacancies, the stronger the luminescence signal, and the greater the production of reactive oxygen species. Further studies revealed that the CL intensity was positively correlated with the oxygen vacancy content on the surface of nano-TiO2. Moreover, there was also a clear correlation between the oxygen vacancies and photogenerated superoxide radicals (O2˙-) on nano-TiO2 suspensions. Therefore, a simple and rapid CL method was developed for evaluating the oxygen vacancy content and their implied ability to photogenerate O2˙- on nano-TiO2 and has great potential in distinguishing surface oxygen vacancies and judging photocatalytic performance in oxides.

A label-free multifunctional nanosensor based on N-doped carbon nanodots for vitamin B12 and Co2+ detection, and bioimaging in living cells and zebrafish

Multifunctional N-doped carbon nanodots (N-CNDs) with a fluorescence (FL) quantum yield (QY) of 13.6% have been synthesized via a facile one-step hydrothermal process using Artemisia annua and 1,2-ethylenediamine as precursors. As-prepared N-CNDs showed excellent FL properties and were developed as a multifunctional sensing platform for vitamin B₁₂ (VB₁₂) and Co²⁺ determination, and bioimaging in living cells and zebrafish. The FL of N-CNDs is quenched efficiently in the presence of VB₁₂ on the basis of the inner filter effect (IFE) or Co²⁺ by static quenching, respectively. EDTA as a masking agent enables Co²⁺ to be effectively eliminated and N-CNDs were used to selectively detect VB₁₂ in the presence of both VB₁₂ and Co²⁺. The present FL nanosensor can detect VB₁₂ and Co²⁺ in the linear ranges of 0.5-35 μM and 2.5-25 μM with the corresponding detection limits of 47.4 nM and 230.5 nM, respectively. The study proved that the determination of Co²⁺ was based on the static quenching to form a complex between the amino group of N-CNDs and Co²⁺. Inspired by these outstanding properties, practical applications of this nanosensor for the detection of VB₁₂ in actual samples (human serum, egg yolk, VB₁₂ tablets and VB₁₂ injection) and Co²⁺ in water samples were further verified with satisfactory results. The as-constructed N-CNDs have negligible toxicity and good biocompatibility, which facilitates utilization of N-CNDs in bioimaging of A549 cells and zebrafish, and sensing VB₁₂ in living cells.

New Single-Layered Paper-Based Microfluidic Devices for the Analysis of Nitrite and Glucose Built via Deposition of Adhesive Tape

A simple, low-cost technique has been developed for the rapid fabrication of single-layered paper-based microfluidic devices (μPADs). This technique, for the first time, made use of the deposition of patterned adhesive tape into the filter paper to construct hydrophobic barriers, with the help of toluene. Unlike other reported multi-layered μPADs that merely made use of adhesive tape as a separate layer for sealing or fluid flow controlling, the patterned adhesive tape was simultaneously dissolved and penetrated into the filter paper, which resulted in the successful transfer of the pattern from the tape to the filter paper. To demonstrate the effectiveness of this approach, nitrite and glucose were individually measured; detection limits as low as 0.015 ± 0.004 mM and 0.022 ± 0.006 mM were reported for nitrite and glucose, respectively. Multiplexed analysis of both analytes was also carried out with respective detection limits of 0.048 ± 0.005 mM and 0.025 ± 0.006 mM for nitrite and glucose. The application of the method was demonstrated by measuring nitrite and glucose in spiked artificial urine samples and satisfied recovery results were obtained.

Silicon nanoparticles synthesized using a microwave method and used as a label-free fluorescent probe for detection of VB12

A simple and rapid detection strategy for vitamin B₁₂ (VB₁₂ ) was established based on label-free silicon quantum dots (SiQDs); the detection mechanism was additionally investigated. SiQDs were synthesized using a one-step microwave method, and their fluorescence was stronger than that synthesized using the hydrothermal method. SiQDs fluorescence was quenched using VB₁₂ due to the inner filter effect (IFE), which was demonstrated using ultraviolet (UV) absorption spectra, fluorescence lifetime, transmission electron microscopy and zeta potential analysis. Subsequently, quercetin (Que) and doxorubicin (Dox) with absorption peaks that overlapped the excitation or emission peaks of SiQDs respectively were used as control groups to investigate the quenching mechanism. Results showed that quenching efficiency was related to the level of overlap between the adsorption peak of the quencher and the excitation or emission peaks of SiQDs. A greater level of overlap caused a higher quenching efficiency. Therefore, the sensitive quenching of VB₁₂ for SiQDs was due to the synergistic effect of the synchronous overlap between the absorption peak of VB₁₂ with the excitation and emission peaks of SiQDs. Fluorescence quenching efficiency increased linearly in the 0.5 to 16.0 μmol·L^-1 VB₁₂ concentration range, and the detection limit was 158 nmol·L^-1 . In addition, SiQDs were applied to determine VB₁₂ in tablets and human urine samples with satisfactory recoveries ranging from 97.7 to 101.1%.

A paper-based colorimetric microfluidic sensor fabricated by a novel spray painting prototyping process for iron analysis

A novel, simple, and low-cost spray painting technique has been developed for the fabrication of microfluidic paper-based devices. The devices that we developed utilize aerosol spray paint to build hydrophobic barriers and employ a hole puncher to obtain paper-based patterned layers and paper dots without using any specialized instruments (e.g., without a laser cutter). The entire manufacturing process is extremely simple, inexpensive, and rapid, which means that it can be applied broadly. Furthermore, the application of the device to iron detection was demonstrated. A linear relationship between the colour value and the iron concentration was observed from 0 to 0.02 g/L. The developed microfluidic paper-based device for iron detection exhibited a low detection limit (0.00090 g/L), good selectivity, and acceptable recovery.

Tuning the chemiluminescence of a luminol flow using plasmonic nanoparticles

We have discovered a strong increase in the intensity of the chemiluminescence of a luminol flow and a dramatic modification of its spectral shape in the presence of metallic nanoparticles. We observed that pumping gold and silver nanoparticles into a microfluidic device fabricated in polydimethylsiloxane prolongs the glow time of luminol. We have demonstrated that the intensity of chemiluminescence in the presence of nanospheres depends on the position along the microfluidic serpentine channel. We show that the enhancement factors can be controlled by the nanoparticle size and material. Spectrally, the emission peak of luminol overlaps with the absorption band of the nanospheres, which maximizes the effect of confined plasmons on the optical density of states in the vicinity of the luminol emission peak. These observations, interpreted in terms of the Purcell effect mediated by nano-plasmons, form an essential step toward the development of microfluidic chips with gain media. Practical implementation of the discovered effect will include improving the detection limits of chemiluminescence for forensic science, research in biology and chemistry, and a number of commercial applications.

Design a New Strategy Based on Nanoparticle-Enhanced Chemiluminescence Sensor Array for Biothiols Discrimination

Array-based sensor is an interesting approach that suggests an alternative to expensive analytical methods. In this work, we introduce a novel, simple, and sensitive nanoparticle-based chemiluminescence (CL) sensor array for discrimination of biothiols (e.g., cysteine, glutathione and glutathione disulfide). The proposed CL sensor array is based on the CL efficiencies of four types of enhanced nanoparticle-based CL systems. The intensity of CL was altered to varying degrees upon interaction with biothiols, producing unique CL response patterns. These distinct CL response patterns were collected as “fingerprints” and were then identified through chemometric methods, including linear discriminant analysis (LDA) and hierarchical cluster analysis (HCA). The developed array was able to successfully differentiate between cysteine, glutathione and glutathione disulfide in a wide concentration range. Moreover, it was applied to distinguish among the above analytes in human plasma.

Amino acids as novel nucleophiles for silver nanoparticle-luminol chemiluminescence

The use of noble metal nanoparticles (NPs) as reductants in chemiluminescence (CL) has been reported only rarely owing to their high oxidation potentials. Interestingly, nucleophiles could dramatically lower the oxidation potential of Ag NPs, such that in the presence of nucleophiles Ag NPS could be used as reductants to induce the CL emission of luminol, an important CL reagent widely used in forensic analysis for the detection of trace amounts of blood. Although nucleophiles are indispensible in Ag NP-luminol CL, only inorganic nucleophiles such as Cl(-), Br(-), I(-) and S2O3 (2-) have been shown to be efficient. The effects of organic nucleophiles on CL remain unexplored. In this study, 20 standard amino acids were evaluated as novel organic nucleophiles in Ag NP-luminol CL. Histidine, lysine and arginine could initiate CL emission; the others could not. It is proposed that the different behaviors of 20 standard amino acids in the CL reactions derive from the interface chemistry between Ag NPs and these amino acids. UV/vis absorption spectra were studied to validate the interface chemistry. In addition, imidazole and histidine were chosen as a model pair to compare the behavior of the monodentate nucleophile with that of the corresponding multidentate nucleophile in Ag NP-luminol CL.

Luminol-based chemiluminescent signals: clinical and non-clinical application and future uses

Chemiluminescence (CL) is an important method for quantification and analysis of various macromolecules. A wide range of CL agents such as luminol, hydrogen peroxide, fluorescein, dioxetanes and derivatives of oxalate, and acridinium dyes are used according to their biological specificity and utility. This review describes the application of luminol chemiluminescence (LCL) in forensic, biomedical, and clinical sciences. LCL is a very useful detection method due to its selectivity, simplicity, low cost, and high sensitivity. LCL has a dynamic range of applications, including quantification and detection of macro and micromolecules such as proteins, carbohydrates, DNA, and RNA. Luminol-based methods are used in environmental monitoring as biosensors, in the pharmaceutical industry for cellular localization and as biological tracers, and in reporter gene-based assays and several other immunoassays. Here, we also provide information about different compounds that may enhance or inhibit the LCL along with the effect of pH and concentration on LCL. This review covers most of the significant information related to the applications of luminol in different fields.

Microfluidic opportunities in the field of nutrition

Nutrition has always been closely related to human health, which is a constant motivational force driving research in a variety of disciplines. Over the years, the rapidly emerging field of microfluidics has been pushing forward the healthcare industry with the development of microfluidic-based, point-of-care (POC) diagnostic devices. Though a great deal of work has been done in developing microfluidic platforms for disease diagnoses, potential microfluidic applications in the field of nutrition remain largely unexplored. In this Focus article, we would like to investigate the potential chances for microfluidics in the field of nutrition. We will first highlight some of the recent advances in microfluidic blood analysis systems that have the capacity to detect biomarkers of nutrition. Then we will examine existing examples of microfluidic devices for the detection of specific biomarkers of nutrition or nutrient content in food. Finally, we will discuss the challenges in this field and provide some insight into the future of applied microfluidics in nutrition.

Chemiluminescence detector based on a single planar transparent digital microfluidic device

We report on a compact and portable prototype of chemiluminescence detector based on a single planar single polar transparent electrowetting-on-dielectrics (EWOD) device. The coupling ground model was proposed to build the EWOD device, which could be driven under a single polar voltage. Such a design not only simplified the chip construction and control circuit, but also had the potential for the ball-like droplet to focus the fluorescence and enhance the detection sensitivity. Simulations and experiments both confirmed that the greater the contact angle, the stronger the detected optical signal, and thus the higher the sensitivity. The sensitivity of the prototype detector to H2O2 was 5.45 mV (mmol L(-1))(-1) and the detection limit was 0.01 mmol L(-1) when the contact angle of the EWOD surface was 120°. To further increase the sensitivity and decrease the detection limit, the contact angle of the EWOD device could be increased and the dark current of the photomultiplier decreased. The prototype shows potential applications as highly sensitive, cost effective and portable immuno-detectors, especially as a blood glucose monitor.