One-shot genetic analysis in monolithic Silicon/Pyrex microdevices

Poly-L-histidine coated microfluidic devices for bacterial DNA purification without chaotropic solutions

We present a disposable polymeric microfluidic device capable of reversibly binding and purifying Salmonella DNA through solid phase extraction (SPE). The microfluidic channels are first oxygen plasma treated and simultaneously micro-nanotextured, and then functionalized with amine groups via modification with L-histidine or poly-L-histidine. L-Histidine and poly-L-histidine bind on the plasma treated chip surface, and are not detached when rinsing with DNA purification protocol buffers. A pH-dependent protocol is applied on-chip to purify Salmonella DNA, which is first bound on the protonated amines at a pH (5.0) lower than their pKa of surface amine-groups which is 6.0 and then released at a pH higher than the pKa value (10.5). It was found that modification with poly-L-histidine resulted in higher surface density of amine groups onto microfluidic channel. Using the chip modified with poly-L-histidine, high recovery efficiency of at least 550 ng of isolated Salmonella DNA as well as DNA purification from Salmonella cell lysates corresponding to less than 5000 cells or 0.026 ng of Salmonella DNA was achieved. The protocol developed does not require ethanol or chaotropic solutions typically used in DNA purification, which are known inhibitors for downstream operations such as polymerase chain reactions (PCR) and which can also attack some polymeric microfluidic materials. Therefore, the microfluidic device and the related protocol hold promise for facile incorporation in microfluidics and Lab-on-a-chip (LOC) platforms for pathogen detection or in general for DNA purification.

Role of oral fluids in DNA investigations

The assay of oral fluid (OF), a biofluid historically well-studied biochemically and physiologically, is a growing area of research with implications for basic and clinical purposes. In the last decade, it has gained considerable attention and lately, the use of OF has provided a substantial addition as an investigative tool in forensic and/or legal procedures. This article is an appraisal of various applications of OF sourced DNA in the field of forensic analysis. We have discussed the significance of different collection methods and their variations along with the application of specific analytical methods based on the condition of the sample. It is likely that the germaneness of OF assays will continue to expand thus providing a new instrument for investigation in criminal/legal proceedings.