A low cost and effective indirect competitive method is reported to detect five EDCs, 17-beta-estradiol (E2), estriol (E3), bisphenol A (BPA), diethylstilbestrol (DES), and nonylphenol (NP) simultaneously, based on suspension array technology (SAT). Five kinds of complete antigens (E2-BSA, E3-BSA, BPA-BSA, DES-BPA, NP-BSA) were coupled to different encoding microspheres using purpose-made solutions in our laboratory instead of commercially available amino coupling kits; the method was further optimized for determination and reducing  the cost. Encoding and signaling fluorescence of the particles are determined at 635/532 nm emission wavelengths. High-throughput curves of five EDCs were draw and the limit of detection (LOD) were between 0.0010 ng mL-1 ~ 0.0070 ng mL-1. Compared with traditional ELISA methods, the SAT exhibited better specificity and sensitivity. Experiments using spiked milk and tap water samples were also carried out, and the recovery was between 85 and 110%; the results also confirmed good repeatability and reproducibility. It illustrated great potential of the present strategy in the detection of EDCs in actual samples.

Nowadays, the biomolecular assay platforms built-up based on bead counting technologies have emerged to be powerful tools for the sensitive and high-throughput detection of disease biomarkers. In this mini-review, we classified the bead counting technologies into statistical counting platforms and digital counting platforms. The design principles, the readout strategies, as well as the pros and cons of these platforms are introduced in detail. Finally, we point out that the digital bead counting technologies will lead the future trend for the absolute quantification of critical biomarkers, and the integration of new signal amplification approaches and routine optical/clinical instruments may provide new opportunities in building-up easily accessible digital assay platforms.

Herein, a novel suspension array of polystyrene (PS) beads for simultaneous recognition and quantification of multiple cancer-associated microRNAs (miRNAs) using flow cytometry has been reported. The suspension array contained three moieties, streptavidin-modified PS beads, biotin-labeled substrate strands (17S) of the 17-8 DNAzyme and two split DNAzyme parts (PA, PB). 17S was labeled with 6-carboxyfluorescein (FAM) and Dabcyl on both sides of the ribonucleic acid. Once the target miRNAs appear, they can bind with the corresponding PA and PB to form an active secondary structure of DNAzyme. The active DNAzyme can cleave 17S and remove Dabcyl from the bead\'s surface, thus recovering the FAM\'s fluorescence intensity. Furthermore, the released target miRNA can autonomously move to the neighboring inactive DNAzyme for further cleavage, thus amplifying the fluorescence signal. Therefore, the target miRNAs can be quantified by reading the fluorescence intensity output from flow cytometry. The PS beads-based suspension array for the target miRNA in buffer shows good selectivity and high sensitivity. Via binding with a different pair of PA and PB, this suspension sensor array has successfully typed and quantified cancer-associated miRNAs of miR-21, miR-155, miR-335, and miR-122 in buffer and serum conditions.

Recent advances in miniaturization of analytical systems and newly emerging technologies offer platforms with greater automation and multiplexing capabilities than traditional biological binding assays. Multiplexed bioanalytical techniques provide control agencies and food industries with new possibilities for improved, more efficient monitoring of food and environmental contaminants. This review deals with recent developments in planar-array and suspension-array technologies, and their applications in detecting pathogens, food allergens and adulterants, toxins, antibiotics and environmental contaminants.

A one-step synthesis using the reversed-phase suspension polymerization method and ultraviolet light curing is proposed for preparing the Raman-encoded suspension array (SA). The encoded microcarriers are prepared by doping the Raman reporter molecules into an aqueous phase, and then dispersing the aqueous phase in an oil phase and curing by ultraviolet light irradiation. The multiplexed biomolecule detection and various concentration experiments confirm the qualitative and quantitative analysis capabilities of the Raman-encoded SA with a limit of detection of 52.68 pM. The narrow bandwidth of the Raman spectrum can achieve a large number of codes in the available spectral range and the independence between the encoding channel and the fluorescent label channel provides the encoding method with high accuracy. This preparation method is simple and easy to operate, low in cost, and high in efficiency. A large number of hydrogel-based encoding microbeads could be quickly obtained with good biocompatibility. Most importantly, concentrating plenty of Raman reporter molecules inside the microbeads increases the signal intensity and means the molecular assembly is not limited by the functional groups; thus, the types of materials available for Raman encoding method are expanded. Furthermore, the signal intensity-related encoding method is verified by doping different proportions of Raman reporter molecules with our proposed synthesis method, which further increases the detection throughput of Raman-encoded SA. Graphical Abstract.

A carbon nanotube (CNT)-mediated antibody-free suspension array (CASA) by integration of functionalized CNTs and aptamer (Apt) into xMAP® technology for simultaneous determination of typical endocrine-disrupting chemicals (EDCs) was developed . The interaction between CNTs and Apt acts as an effective and straightforward signal recognition, transformation, and amplification strategy. The amino-functionalized CNTs are covalently modified on the carboxyl-functionalized magnetic bead (MB) and further physically bridging with biotinylated Apt. CNTs on the surface of MBs not only increase the amount of Apt for target binding and signal amplification but also maintain the biological activity of Apt. After magnetic separation, the encoded MB address was distinguished and the concentration of the target in the liquid was negatively correlated with median fluorescence intensity. A series of environmental water samples were analysed by CASA, traditional immuno-SA, and competitive inhibition enzyme-linked immunosorbent assay for validation. The results obtained using CASA well matched for the multiplexed detection of various targets with dynamic concentration range from 6.40 × 10-5 to 4.00 μg L-1 within 1 h. The method also confirmed good selectively, accuracy, and consistency with high-performance liquid chromatography. Graphical abstractSchematic representation of amino-functionalized carbon nanotube (CNT)-bridged antibody-free suspension array for detecting of three typical endocrine-disrupting chemicals. The amino-functionalized CNTs are covalently modified and further physically interacted with biotinylated aptamer featuring in the recognition and binding with the target of interest.

The need for high-throughput screening has led to the miniaturization of the reaction volume of the chamber in bioassays. As the reactor gets smaller, surface tension dominates the gravitational or inertial force, and mixing efficiency decreases in small-scale reactions. Because passive mixing by simple diffusion in tens of microliter-scale volumes takes a long time, active mixing is needed. Here, we report an efficient micromixing method using magnetically rotating microparticles with patterned magnetization induced by magnetic nanoparticle chains. Because the microparticles have magnetization patterning due to fabrication with magnetic nanoparticle chains, the microparticles can rotate along the external rotating magnetic field, causing micromixing. We validated the reaction efficiency by comparing this micromixing method with other mixing methods such as simple diffusion and the use of a rocking shaker at various working volumes. This method has the potential to be widely utilized in suspension assay technology as an efficient mixing strategy.

We proposed a coding and decoding method of suspension array (SA) based on micro-quartz pieces (MQPs) with different optical thicknesses. The capture probes (cDNA) were grafted onto the surfaces of MQPs and specifically recognized and combined with the partial sequence of the target DNA (tDNA) to form a MQP-cDNA-tDNA complex. Quantum dot-labeled signal probes were then used to specifically recognize and bind another portion of the tDNA in the complex to form a double-probe sandwich structure. This optical thickness-encoded SA can be decoded and detected by a dual-wavelength digital holographic phase fluorescence microscope system. We conducted a series of DNA molecule detection experiments by using this encoding method. Control experiments confirmed the specificity of optical thickness-encoded SA in DNA detection. The concentration gradient experiments then demonstrated the response of the MQPs based SA to analyte concentration. Finally, we used the encoding method to detect three types of DNA in a single sample and confirmed the feasibility of the proposed optical thickness-encoded SA in multiplexed DNA detection. The detection results are stable, and the detection exhibits high specificity and good repeatability.

BACKGROUND: Meat fraud and adulteration incidents occur frequently in almost all regions of the globe, especially with the increase in the world\'s population. To ensure the authenticity of meat products, we developed a 10-plex xMAP assay to simultaneously detect ten animal materials: bovine, caprine, poultry, swine, donkey, deer, horse, dog, fox and mink.
RESULTS: This method was investigated by analyzing DNA extracts from raw muscle, muscle mixtures, meat products and animal feeds. Our results indicated that the species of interest can be identified, differentiated and detected down to 1 g kg-1 in binary mixtures or 0.01-0.001 ng of genomic DNA from specific species. Testing of 125 commercial samples showed a 97.4% coincidence rate with the method used in routine testing in our lab.
CONCLUSIONS: These results indicated that the method established in this study could detect ten animal materials simultaneously within 3 h, which provides a new, useful tool for animal ingredient analysis in meat products and animal feeds. © 2019 Society of Chemical Industry.

OBJECTIVE: More than 50% of congenital hearing loss is attributed to genetic factors. Data of gene mutation associated with hearing loss from large population studies in Chinese population are scarce. In this study, we conducted a comprehensive newborn genetic screening in China to establish the carrier frequency and mutation spectrum of deafness-associated genes.
METHODS: A total of 53,033 newborns were screened for hearing defects associated mutations. Twenty hot spot mutations in GJB2, GJB3, SLC26A4 and mitochondria12S rRNA were examined using suspension array analysis.
RESULTS: 14,185 newborns (26.75%) were identified with at least one mutated allele. 872 (1.64%) neonates carried homozygous mutations including 112 (0.21%) mitochondrial DNA homoplasmy, 228 (0.43%) were compound heterozygotes, and 11,985 (22.59%) were heterozygotes including 11 (0.02%) mitochondrial DNA heteroplasmy. Top five mutations included 109 G > A, 235 delC, 299-300 delAT in GJB2, IVS7-2 A > G in SLC26A4 and 1555 A > G in mitochondria12S rRNA. Notably, a total of 10,995 neonates (20.73%) carried 109 G > A in GJB2. Moreover, the allele frequencies of 109 G > A were detected 11.61% in Guangdong, 10.44% in Sichuan and 2.88% in Shandong, respectively, a significant difference in prevalence among these geographic regions (p<0.01). In addition, the high frequency of 109 G > A in GJB2 was confirmed by a TaqMan probe-based qPCR assay. Very recently, the ClinGen Hearing Loss Expert Panel reached a consensus and confirmed its pathogenic role in hearing impairment.
CONCLUSIONS: We delineated the mutation profile of common deafness-causing genes in the Chinese population and highlighted the high prevalence of 109 G > A pathogenic mutation. Our study may facilitate early diagnosis/intervention and genetic counseling for hearing impairment in clinical practice.