ABSTRACT
BACKGROUND: Loxoscelism is the envenomation caused by the bite of Loxosceles spp. spiders. It entails severe necrotizing skin lesions, sometimes accompanied by systemic reactions and even death. There are no diagnostic means and treatment is mostly palliative. The main toxin, found in several isoforms in the venom, is sphingomyelinase D (SMD), a phospholipase that has been used to generate antibodies intended for medical applications. Nucleic acid aptamers are a promising alternative to antibodies. Aptamers may be isolated from a combinatorial mixture of oligonucleotides by iterative selection of those that bind to the target. In this work, two Loxosceles laeta SMD isoforms, Ll1 and Ll2, were produced in bacteria and used as targets with the aim of identifying RNA aptamers that inhibit sphingomyelinase activity. RESULTS: Six RNA aptamers capable of eliciting partial but statistically significant inhibitions of the sphingomyelinase activity of recombinant SMD-Ll1 and SMD-Ll2 were obtained: four aptamers exert ~17% inhibition of SMD-Ll1, while two aptamers result in ~25% inhibition of SMD-Ll2 and ~18% cross inhibition of SMD-Ll1. CONCLUSIONS: This work is the first attempt to obtain aptamers with therapeutic and diagnostic potential for loxoscelism and provides an initial platform to undertake the development of novel anti Loxoscelesvenom agents.
Subject(s)
Animals , Aptamers, Nucleotide/isolation & purification , Aptamers, Nucleotide/metabolism , Phosphoric Diester Hydrolases , Phosphodiesterase Inhibitors/isolation & purification , Spider Venoms/enzymology , Aptamers, Nucleotide/therapeutic use , Brown Recluse Spider/enzymology , Chromatography, Affinity , Cloning, Molecular , Gene Expression/genetics , Phosphodiesterase Inhibitors , Phosphodiesterase Inhibitors/pharmacology , Phosphoric Diester Hydrolases/classification , Sequence Analysis, DNA/methods , Spider Bites/drug therapy , Spider Venoms/classificationABSTRACT
OBJECTIVE@#To select specific DNA aptamer for determining ketamine by FluMag-SELEX.@*METHODS@#Based on magnetic beads with tosyl surface modification as solid carrier and ketamine as target, a random ssDNA library with total length of 78 bp in vitro was compounded. After 13 rounds screening, DNA cloning and sequencing were done. Primary and secondary, structures were analyzed. The affinity, specificity and Kd values of selected aptamer were measured by monitoring the fluorescence intensity.@*RESULTS@#Two ssDNA aptamers (Apt#4 and Apt#8) were successfully selected with high and specific abilities to bind ketamine as target with Kd value of 0.59 and 0.66 μmol/L. The prediction of secondary structure was main stem-loop and G-tetramer. The stem was the basis of stability of aptamer's structure. And loop and G-tetramer was the key of specific binding of ketamine.@*CONCLUSION@#FluMag-SELEX can greatly improve the selection efficiency of the aptamer, obtain the ketamine-binding DNA aptamer, and develop a new method for rapid detection of ketamine.