DNA methylation detection by a novel fluorimetric nanobiosensor for early cancer diagnosis.

A very sensitive and convenient fluorescence nanobiosensor for rapid detection of DNA methylation based on Fe3O4/Au core/shell nanoparticles has been developed. Specific site of CpG islands of adenomatous polyposis coli (APC), a well studied tumor suppressor gene, was used as the detection target DNA sequence. The characteristics of nanoparticles were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), UV-visible spectroscopy and X-ray diffraction (XRD) spectroscopy. Fe@Au nanoparticles functionalized by bounding of single stranded DNA (ssDNA) probe through sulfhydryl group at the 5' phosphate end. Then unmethylated and methylated complementary target ssDNA were hybridized with the immobilized ssDNA probe. Dipyridamole, a pharmaceutical agent used for the first time as a fluorescence probe which significantly interacted with hybridized unmethylated and methylated DNA. Upon the addition of the target unmethylated and methylated ssDNA, the fluorescence intensity increased in linear range by concentration of unmethylated ssDNA from 1.6 × 10(-15) to 6.6 × 10(-13)M with detection limit of 1.2 × 10(-16)M and on the other hand, fluorescence intensity declined linearly with concentration of 3.2 × 10(-15)-8.0 × 10(-13)M methylated DNA and detection limit was 3.1 × 10(-16)M. We have also shown that nanobiosensor could distinguish ratio of methylation in series of partially methylated DNA targets with identical sequences. A density functional theory (DFT) calculation was also performed to investigate the interaction between Dipyridamole with unmethylated and methylated cytosine. Finally real sample analysis suggested that nanobiosensor could have practical application for methylation detection in human plasma sample.

Interaction of hypertension and diabetes on renal function in black NIDDM subjects.

We studied renal function of 194 black subjects with duration of diagnosed NIDDM from 1 month to 36 years to determine the interaction of hypertension and diabetes on nephropathy. Renal function was assessed by isotopic GFR and RPF studies, and serum creatinine. One hundred seventeen of the 194 subjects had 24-hour urinary albumin excretion (AER). AER > 300 mg/24 h correlated with longer duration of NIDDM, decrease in GFR and RPF, and rise in serum Cr, and all subjects were hypertensive. AER 30 to 300 mg/24 h also correlated with a longer duration of NIDDM and 80% had hypertension. When 194 subjects were grouped according to duration of NIDDM and the presence or absence of hypertension, subjects who remained normotensive had normal renal function. In hypertensive subjects a decrease in GFR occurred with duration of NIDDM > 1 year and decrease in RPF with duration of NIDDM > 5 years. In hypertensive subjects with NIDDM > 10 years, 36% had impaired renal function (GFR < 80 ml/min/1.73 m2 or serum creatinine > 1.4 mg/dl) and 75% had microalbuminuria or clinical proteinuria. Within this group, those subjects who developed hypertension after their diagnosis of diabetes were likely to have evidence of nephropathy as compared to those subjects whose hypertension was diagnosed prior to or simultaneous with their diabetes: 17 of 20 (85%) versus 7 of 13 (54%), respectively (P = 0.05). These data provide insight into the relationship between hypertension and diabetes in the development of nephropathy in black NIDDM individuals.