Indradumna Banerjee,1 Tagrid Salih,1 Anna Ohlander,2 and Aman Russom.1
Affiliates: [1] Division of Proteomics and Nanobiotechnology, KTH Royal Institute of Technology, Stockholm. Sweden. [2] Fraunhofer EMFT, Hansastrasse 27d, 80686 Munich, Germany.

We present a three dimensional slipdisc aimed at quantification of viral load in resource limited settings. The technique is a hybrid of Slipdisc technology, lab on foil technique and immiscible phase filtration achieved by adding an extra fluidic layer to Slipdisc. A lab on foil heater is used to heat the elution buffer in the detection chamber to carry out a LAMP assay.

Slipdisc, iFAST, Immiscible phase filtration, three dimensional slipchip technology, Lab on foil.

In this study, we introduce a three dimensional Slipdisc1 based on slipchip technology, aimed to be used at detection of HIV-1 viral load in resource limited settings. This method is based on magnetic bead based isolation of RNA from sample, followed by release of RNA in an elution buffer, followed by amplification of the initial concentration of RNA in an elution buffer. The novelty is the extraction method which is a one step method and involves using magnetic beads attached to sample DNA to pass through an immiscible oil phase2 for one step washing.

The three dimensional Slipdisc is based on a clockwork mechanism, involving a top plexiglass holder with grooves sequentially moving over a bottom counterpart maintained with four clocksprings. The clocksprings are initially engaged in the mini-grooves and the clockwork is in a semi locking position (Fig.1). However, the three dimensional slipdisc is different from the original Slipdisc due to the incorporation of a third fluidic layer on top of the original two layers. The top and middle superhydrohobic coated discs are placed on the bottom holder which has a slot cut out to accommodate the discs. After the slip step the bottom disc comes in direct contact with the topmost disc and magnetic beads can be transferred in between the top and the bottom layers (Fig.2). The top holder is mounted and locked through the same slot previously used to secure the bottom holder and the discs. The samples are loaded via apertures cut out on the top holder when the discs are placed onto their positions and the clockwork is engaged or in locked position. A fluidic path is established along a hydrophilic channel between the two discs.

Results and discussion
A one step extraction method is developed using food dyes such that magnetic beads attached to RNA pass from what is supposedly a lysis buffer to the elution buffer chamber through an immiscible oil phase (fig.2). The method is presently illustrated with food dyes. The elution buffer chamber is equipped with a lab on foil3 which is used to heat the elution buffer chamber to a temperature of 65 degree Centigrade. A characterization of a lab on foil heater with Temperature sensitive crystals is shown in fig.3. The range of colors on the crystals correspond to a temperature of 65 degree Centigrade.

A unique device combining three different lab on chip techniques: Slipdisc, lab on foil and iFAST is presented which can be a true answer to the mostly unmet need of a point of care device battery driven device for HIV diagnostics at resource limited settings. Currently, the device is being developed and soon is supposed to be tested with clinical samples.

1. Banerjee, I., et al. RSC Advances 7.56 (2017): 35048-35054.
2. Berry, Scott, et. al. Lab on a chip 11.10 (2011): 1747-1753.
3. Ohlander, Anna, et al. Lab on a Chip 13.11 (2013): 2075-2082.