Miniaturized devices towards an integrated lab-on-a-chip platform for DNA diagnostics

Abstract

Microfluidics is an emerging technology enabling the development of Lab-on-a-chip (LOC) systems for clinical diagnostics, drug discovery and screening, food safety and environmental analysis. LOC systems integrate and scale down one or several laboratory functions on a single chip of a few mm 2 to cm 2 in size, and account for many advantages on biochemical analyses, such as low sample and reagent consumption, low cost, reduced analysis time, portability and point-of-need compatibility. Currently, available nucleic acid diagnostic tests take advantage of Polymerase Chain Reaction (PCR) that allows exponential amplification of portions of nucleic acid sequences that can be used as indicators for the identification of various diseases. Here, we present a comparison between static chamber and continuous flow miniaturized PCR devices, in terms of energy consumption for devices fabricated on the same material stack, with identical sample volume and channel dimensions. The comparison is implemented by a computational study coupling heat transfer in both solid and fluid, mass conservation of species, and joule heating. Based on the conclusions of this study, we develop low-cost and fast DNA amplification devices for both PCR and isothermal amplification, and we implement them in the detection of mutations related to breast cancer. The devices are fabricated by mass production amenable technologies on printed circuit board (PCB) substrates, where copper facilitates the incorporation of on-chip microheaters, defining the thermal zones necessary for PCR or isothermal amplification methods.

The lab-on-PCB approach: tackling the μTAS commercial upscaling bottleneck

“…115,116 Furthermore, microfluidic devices for DNA amplification have been fabricated on 4-copper layer PCB substrates by using either CNC machining or photolithography of industrially used dry film photosensitive resists, for the formation of meandering microfluidic channels. 117,118 In the latter work also, copper facilitates the incorporation of on-chip resistive microheaters, serving both as thermal zones necessary for DNA amplification (Fig. 8A) and as temperature sensors 114 implemented for temperature regulation.…”

Miniaturized devices for isothermal DNA amplification addressing DNA diagnostics

“…They have a meandering shape, to maximize their electrical resistance in the space allocated for each thermal zone. Then, the microfluidic network is patterned by means of computer numerical control (CNC) micromilling, expanding the fabrication capability made possible by photolithography of thin dry films (Kaprou et al 2015) to higher microchannel depths. The design of the fluidic network is introduced using a Gerber file.…”

“…In addition to the work in (Kaprou et al 2015), an evaluation was performed employing the microdevice with the HDA method using Salmonella genomic DNA in order to detect Salmonella strains stemming from a 500 bacteria culture after cell lysis and purification step (Tsougeni et al 2016). This is a common procedure used in food safety controls.…”

“…In this work, we develop low-cost devices for fast DNA amplification (Kaprou et al 2015), focusing on HDA, and we implement them in the detection of mutations related to breast cancer as well as Salmonella detection. Genetic analysis of mutations in BRCA1 gene that are associated with breast and ovarian cancer is routine in many molecular biolog y laboratories and most of the detection methods employed are based on DNA amplification combined with fluorescent labels or gel electrophoresis.…”

Towards PCB-Based Miniaturized Thermocyclers for DNA Amplification

“…In the case of the thin microheater, a two-copper layer PCB was employed, with the resistive microheater patterned on one of the external copper layers reaching a resistance value of 23 Ohm, whereas the second one was used as a solid copper surface to improve the temperature uniformity across the heated area. The temperature coefficient of resistance for the copper track was determined in a previous work to be 0.0036 ± 0.0002 • C −1 [27].…”