A Simple, Rapid, and Highly Sensitive Electrochemical DNA Sensor for the Detection of α- and β-Thalassemia in China

Alpha and beta-Thalassemia mutations in Hubei area of China

Background

Thalassemia is a group of inherited hemoglobic disorders resulting from defects

in the synthesis of one or more of the hemoglobin chains, which is one of the most prevalent inherited disorders in southern China. Only few studies reported the molecular characterization of α- and β-Thalassemia in Hubei Province in the central of China.

Methods

A total of 4889 clinically suspected cases of thalassemia were analyzed by Gap-PCR, PCR-based reverse dot blot (RDB).

Results

1706 (33.8%) subjects harbored thalassemia mutations, including 539 (11.0%) subjects with α-thalassemia, 1140 (23.3%) subjects with β-thalassemia mutations, and 25 (0.51%) subjects with both α- and β-thalassemia mutations. Seven genotypes of α-thalassemia mutations and 29 genotypes of β-thalassemia mutations were characterized. --^SEA/αα (66.05%), −α^3.7/αα (24.12%), and -α^4.2/αα (3.71%) accounted for 93.88% of the α-thalassemia mutations. βIVS-II-654/βN, βCD41–42/βN, βCD17/βN, βCD27–28/βN, βCD71–72/βN, β − 28/βN, β − 29/βN, βCD43/βN, βE/βN, accounting for 96.40% of all β-thalassemia genotypes. Furthermore, mean corpuscular volume (MCV) and mean corpuscular Hb (MCH) were sensitive markers for both β-thalassemia and α-thalassemia with --^SEA/αα, but not -α^3.7/αα and -α^4.2/αα. Conclusions: Our data indicated great heterogeneity and extensive spectrum of thalassemias in Hubei province of China.

Electrochemical nucleic acid hybridization biosensor based on poly(L-Aspartic acid)-modified electrode for the detection of short oligonucleotide sequences related to hepatitis C virus 1a

This work describes, for the first time, the fabrication of poly(L-aspartic acid) (PAA) film modified pencil graphite electrode (PGE) for the detection of hepatitis C Virus 1a (HCV1a). The presence of PAA on the electrode surface can provide free carboxyl groups for covalent binding of biomolecules. The PGE surface was first coated with PAA via electropolymerization of the L-aspartic acid, and avidin was subsequently attached to the PAA modified electrode by covalent attachment. Biotinylated HCV1a probes were immobilized on avidin/PAA/PGE via avidin-biotin interaction. The morphology of PAA/PGE was examined using a scanning electron microscope. The hybridization events were monitored with square wave voltammetry using Meldola's blue (MDB). Compared to non-complementary oligonucleotide sequences, when hybridization was carried out between the probe and its synthetic targets or the synthetic polymerase chain reaction analog of HCV1a, the highest MDB signal was observed. The linear range of the biosensor was 12.5 to 100 nM and limit of detection was calculated as 8.7 nM. The biosensor exhibited favorable stability over relatively long-term storage. All these results suggest that PAA-modified electrode can be used to nucleic acid biosensor application and electropolymerization of L-aspartic acid can be considered as a good candidate for the immobilization of biomolecules.

Analysis of Gene Mutation Types of α- and β-Thalassemia in Fuzhou, Fujian Province in China

The aim of this study was to explore the type and distribution of α- and β-thalassemia (α- and β-thal) mutations/deletions in Fuzhou, Fujian Province, People's Republic of China (PRC). For patients whose mean corpuscular volume (MCV) and mean corpuscular hemoglobin (Hb) (MCH) conforms to the characteristics of thalassemia, gap-polymerase chain reaction (gap-PCR) and PCR-reverse dot-blot assays were used to detect α- and β-thal mutations/deletions. Four hundred and twenty-eight cases of thalassemia were detected in 752 suspected cases of thalassemia, including 248 cases of α-thal (57.9%), 175 cases of β-thal (40.9%), and five cases of compound α/β-thal (1.2%). The major genetic types of α-thal were - -^SEA (Southeast Asian; HBA1) and -α^3.7 (rightward; HBA2) deletions, and the carrier rate was 24.9 and 3.3%, respectively. The major genetic types of β-thal were IVS-II-654 (C>T) (HBB: c.316-197C>T), codons 41/42 (-TTCT) (HBB: c.126_129delCTTT), codon 17 (A>T) (HBB: c.52A>T), codons 27/28 (+C) (HBB: c.84_85insC) and -28 (A>G) (HBB: c.-78A>G), and the carrier rate was 9.8, 7.3, 3.5, 1.1 and 0.8%, respectively. The genotypes of α- and β-thal in Fuzhou (Fujian Province, PRC) are characterized by a wide range of distribution, high carrier rate, genetic diversity and genetic heterogeneity. Therefore, it is necessary to detect the thalassemia mutations in the suspected population of this area.

Development of Visual Detection of α-Thalassemia-1 (the - -SEA Deletion) Using pH-Sensitive Loop-Mediated Isothermal Amplification

Detection of α-thalassemia-1 (α-thal-1) carriers provides valuable insight for genetic consulting in prevention and control programs for couples who are at risk of conceiving a fetus with severe thalassemia, both Hb Bart's hydrops fetalis and hemolytic Hb H disease. The traditional method is complicated, time-consuming and requires high instrument cost and expertise. Loop-mediated isothermal amplification (LAMP) based on pH-sensitive dye technology, shows all the characteristics required of a real-time analysis with simple operation for potential use in the clinical diagnosis of high incidence α-thal-1 [Southeast Asian (SEA) or - -^SEA deletion]. Four primers specific for six distinct regions of the α-globin gene deletion were designed and analyzed by LAMP using the pH-indicator dye, phenol red. The amplification of the - -^SEA deletion changed the color of phenol red from pink to orange. The diagnostic ability of detection of the - -^SEA deletion by pH-sensitive LAMP was validated using both known and unknown blood samples and compared to the conventional polymerase chain reaction (PCR) method. Color inspection of pH-sensitive LAMP products could clearly identify the - -^SEA deletion. There was no cross reaction with a normal α-globin gene, α-thal-1 Thai (- -^THAI deletion), α-thal-2 [-α^3.7 (rightward) and -α^4.2 (leftward) deletion] and β-thalassemia (β-thal). Detection of the SEA deletion by pH-sensitive LAMP was consistent as compared to conventional PCR. The pH-sensitive LAMP method developed for this deletion carrier diagnosis has high sensitivity, specificity, simplicity, and requires simple instrumentation that makes it applicable for resource-limited laboratories in rural areas of developing countries.

Investigating the potential of multiwalled carbon nanotubes based zinc nanocomposite as a recognition interface towards plant pathogen detection

The emergence of nanotechnology has opened new horizons for constructing efficient recognition interfaces. This is the first report where the potential of a multiwalled carbon nanotube based zinc nanocomposite (MWCNTs-Zn NPs) investigated for the detection of an agricultural pathogen i.e. Chili leaf curl betasatellite (ChLCB). Atomic force microscope analyses revealed the presence of multiwalled carbon nanotubes (MWCNTs) having a diameter of 50-100nm with zinc nanoparticles (Zn-NPs) of 25-500nm. In this system, these bunches of Zn-NPs anchored along the whole lengths of MWCNTs were used for the immobilization of probe DNA strands. The electrochemical performance of DNA biosensor was assessed in the absence and presence of the complementary DNA during cyclic and differential pulse voltammetry scans. Target binding events occurring on the interface surface patterned with single-stranded DNA was quantitatively translated into electrochemical signals due to hybridization process. In the presence of complementary target DNA, as the result of duplex formation, there was a decrease in the peak current from 1.89×10^-04 to 5.84×10^-05A. The specificity of this electrochemical DNA biosensor was found to be three times as compared to non-complementary DNA. This material structuring technique can be extended to design interfaces for the recognition of the other plant viruses and biomolecules.