alkylation of dna br Experimental br Results and discussion

Experimental
Results and discussion
Conclusion A proof of concept direct conversion solid-state alkylation of dna dosimeter was fabricated by combining the large neutron capture cross-section of 10B with the charge trapping attributes of double layer sub-2nm Pt nanoparticles (Pt NPs) in scalable MOSCAP structures, where the planar neutron conversion layer doubles as the device dielectric. This device architecture successfully generates and traps electrons in the event of successful neutron capture, creating a measurable change in an ex-situ dosimeter response. The strong Coulomb blockade effect of the dual layer Pt NP structure is utilized to improve the charge retention capability significantly. The shift in C–V curve before and after neutron exposure is representative of the resultant generated electrons (after neutron exposure of the 10B-enriched dielectric) being trapped at the NP layer and can be used as a dosimeter. Tunable sensor dynamic range and sensitivity were also demonstrated by adjusting the gate voltage for monitoring the change in capacitance. These devices can be potentially used for in-situ neutron detection if the C–V characteristics are monitored in real-time with a specific sampling rate. The reported neutron detection mechanism in this study can be beneficial to advance the field of neutron detection and lead to future development of novel neutron detectors.
Acknowledgments This work was supported by the National Science Foundation under grant Nos. GOALI-0802157 and GOALI-1232178, as well as NanoTechnology Enterprise Consortium contract No. W15QKN-11-9-0001-RPP1. We would like to thank Dr. Charles Darr for his assistance with the manuscript preparation.
Introduction Magnetic nano-particles or magnetic beads show potential as bio-markers for medical diagnostics resulting from their unique physical properties that include high surface area to volume ratio, compatibility with biological samples and ability to be manipulated by external magnetic fields [8,12,15]. These properties of micro and nanosized magnetic particles have led to reports of lab on chip applications [14] with for example, Burls et al. demonstrating the detection of the cardiac marker Troponin I at sub-pico moles per liter concentrations with low cost disposable cartridges and the importance of the dynamic control of nanoparticles by magnetic fields during detection [1]. However, biosensing platforms based on magnetic nanoparticles can be adversely affected by sensor noise primarily from two primary sources: First non-specific binding of magnetic nanoparticles to sensor surfaces that produces erroneous excess signals, and secondly, detection techniques using magnetoresistive sensors such as giant magnetoresistance (GMR) sensors and Hall effect devices experience sensor noise due to external magnetic fields applied to manipulate nanoparticles [7].In this paper we report on the design and implementation of a sensing platform devised to resolve both of these issues by minimizing the non-specific binding of nanoparticles to sensing areas and optical detection of fluorescent magnetic nanoparticles. Magnetic nanoparticles can be manipulated with permanent magnets, micro-machined micro magnets, and micrometer sized current carrying lines [10]. Current lines provide the most precise localized control of particles on sensing surfaces and have been used to determine bonding forces between biotin & avidin [11]. Most of the current line patterns for biosensing reported to date have implemented linear current lines with only a few reports about circular lines [4,6]. Here we experimentally show that circular current lines are more efficient at collecting magnetic particles than linear current lines. This is supported by theoretical calculations of the forces produced by the two which show that the circular lines produce higher forces than the linear pattern and thus have a higher capture cross section for attracting MNPs to the sensing area. This effect is important for improving the speed and sensitivity of this sensing platform. Furthermore, sensitivity is improved by detecting the light from fluorescent magnetic nanoparticles rather than GMR or other such sensors thereby significantly reducing magnetic sensor noise described previously mentioned. Based on our experimental results, we estimate the theoretical limit of detection of our method to be 0.24pg/mL (1pM) for 180nm diameter fluorescent nanoparticles functionalized with biotin molecules.