Smartphone-assisted fluorescence-based detection of sunrise-type smart amplification process and a 3D-printed ultraviolet light-emitting diode device for the diagnosis of tuberculosis

Accurate and rapid diagnosis of infectious diseases plays a key role in clinical practice, especially in resource-limited countries. In this study, we integrated sunrise-type smart amplification process (s-SmartAmp), a convenient and sensitive isothermal amplification method for nucleic acid, into a portable 3D-printed device equipped with smartphone-assisted image analysis capabilities to develop a novel fluorescence-based sensing system for the on-site diagnosis of tuberculosis (TB). To increase the efficiency of fluorescence (or Förster) resonance energy transfer, two types of sunrise probe systems were compared to detect the IS6110 DNA sequence of TB. Subsequently, linear regression was conducted to compare the performance of s-SmartAmp and loop-mediated isothermal amplification (LAMP). The results indicated that, compared with LAMP, s-SmartAmp yielded more stable and precise results with lower background interference and high linear correlation coefficients (R2 = 0.9994 and 1, respectively) for the FAM-TAMRA and FITC-BHQ-1 probe system. The detection time was 45 min with a detection limit of 10 fg/μL. To evaluate the performance of our proposed on-site sensing system, we used s-SmartAmp 3D-printed ultraviolet light-emitting diode device to test multiple clinical samples of TB. Our findings suggest that the proposed system has the potential to achieve accurate and rapid on-site diagnosis of TB.

Copper nanoclusters on specific-primer PCR fragments with magnetic capture for the label-free fluorescent sensing of the T315I single nucleotide variant in the BCR–ABL1 gene

A simple and facile strategy using the all or none formation of dsDNA-templated copper nanoclusters on specific-primer PCR fragments was designed to fluorescently identify the T315I single nucleotide variant on the BCR–ABL1 gene.

Molecular inversion probe-rolling circle amplification with single-strand poly-T luminescent copper nanoclusters for fluorescent detection of single-nucleotide variant of SMN gene in diagnosis of spinal muscular atrophy

In this study, a simple fluorescent detection of survival motor neuron gene (SMN) in diagnosis of spinal muscular atrophy (SMA) based on nucleic acid amplification test and the poly-T luminescent copper nanoclusters (CuNCs) was established. SMA is a severely genetic diseases to cause infant death in clinical, and detection of SMN gene is a powerful tool for pre- and postnatal diagnosis of this disease. This study utilized the molecular inversion probe for recognition of nucleotide variant between SMN1 (c.840 C) and SMN2 (c.840 C  >  T) genes, and rolling circle amplification with a universal primer for production of poly-T single-strand DNA. Finally, the fluorescent CuNCs were formed on the poly-T single-strand DNA template with addition of CuSO₄ and sodium ascorbate. The fluorescence of CuNCs was only detected in the samples with the presence of SMN1 gene controlling the disease of SMA. After optimization of experimental conditions, this highly efficient method was performed under 50 °C for DNA ligation temperature by using 2U Ampligase, 3 h for rolling circle amplification, and the formation of the CuNCs by mixing 500 μM Cu²⁺ and 4 mM sodium ascorbate. Additionally, this highly efficient method was successfully applied for 65 clinical DNA samples, including 4 SMA patients, 4 carriers and 57 wild individuals. This label-free detection strategy has the own potential to not only be a general method for detection of SMN1 gene in diagnosis of SMA disease, but also served as a tool for detection of other single nucleotide polymorphisms or nucleotide variants in genetic analysis through designing the different sensing probes.

Fluorescent Double-Stranded DNA-Templated Copper Nanoprobes for Rapid Diagnosis of Tuberculosis

In this work, we investigate highly sensitive fluorescent Cu nanoparticles for use as rapid and specific nucleic acid amplification nanoprobes (NPs) for the diagnosis of tuberculosis. After applying polymerase chain reaction (PCR) to a tuberculosis (TB) sample, we demonstrate that the presence of the targeted IS6110 DNA sequence of TB can be easily and directly detected through the in situ formation of DNA-templated fluorescent Cu NPs and subsequently quantified using only a smartphone. Compared to traditional DNA analysis, this sensing platform does not require purification steps and eliminates the need for electrophoresis to confirm the PCR results. After optimization, this dsDNA-Cu NP-PCR method has the ability to analyze clinical TB nucleic acid samples at a detection limit of 5 fg/μL, and the fluorescent signal can be distinguished in only ∼3 min after the DNA has been amplified. Moreover, with the combination of smartphone-assisted imaging analysis, we can further reduce the instrument size/cost and enhance the portability. In this manner, we are able to eliminate the need for a fluorescent spectrophotometer to measure the clinical sample. These results demonstrate this platform's practical applicability, combining a smartphone and on-site analysis while retaining the detection performance, making it suitable for clinical DNA applications in resource-limited regions of the world.

Ultrasensitive turn-on fluorescent detection of trace thiocyanate based on fluorescence resonance energy transfer

Thiocyanate (SCN(-)) is a small anion byproduct of cyanide metabolism. Several methods have been reported to measure SCN(-) above the micromolar level. However, SCN(-) is derived from many sources such as cigarettes, waste water, food and even car exhaust and its effect is cumulative, which makes it necessary to develop methods for the detection of trace SCN(-). In this paper, a simple and ultrasensitive turn-on fluorescence assay of trace SCN(-) is established based on the fluorescence resonance energy transfer (FRET) between gold nanoparticles (AuNPs) and fluorescein. The detection limit is 0.09 nM, to the best of our knowledge, which has been the lowest detection LOD ever without the aid of costly instrumentation. The fluorescence of fluorescein is significantly quenched when it is attached to the surface of AuNPs. Upon the addition of SCN(-), the fluorescence is turned on due to the competition action between SCN(-) and fluorescein towards the surface of AuNPs. Under an optimum pH, AuNPs size and concentration, incubation time, the fluorescence enhancement efficiency [(IF-I0)/I0] displays a linear relationship with the concentration of SCN(-) in the range of 1.0 nM to 40.0 nM. The fluorescein-AuNP sensor shows absolutely high selectivity toward SCN(-) than other 16 anions. The common metal ions, amino acids and sugars have no obvious interference effects. The accuracy and precision were evaluated based on the recovery experiments. The cost effective sensing system is successfully applied for the determination of SCN(-) in milk products and saliva samples.