IVDT_In Vitro Diagnostics Technology

IVD Technology, November/December 2012

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MOLECULAR DIAGNOSTICS would like to make a decision before the patient leaves the offi ce. For example, treatment of infl uenza virus is very time- sensitive and requires rapid results. Current lateral fl ow antigen-based tests satisfy the requirements for rapid tests; however, they suff er from rela- tively poor sensitivity.3 Portrait PA5000 System Overview C D B A A B Th e system described herein, termed Portrait PA5000, is a sample- to-result test platform (Figure 3). It is designed to require no user main- tenance and to be easy to operate through a simple user interface. Liquid clinical specimens are loaded into a self-contained single-use cartridge that contains all of the reagents necessary and collects all waste. Th e customer then enters patient information and initiates a test routine performed by the instrument; no additional hands- on steps are required. Cartridge Th e cartridge is designed as a meso- fl uidic device, processing relatively large microliter volumes to avoid the physical eff ects of fl uids that can be diffi cult to manage in microfl uidic devices. Th e cartridge contains all reagents necessary to perform the assay in blister packs except for the ampli- fi cation reagents, which are stored as a lyophilized pellet. Th e base of the injection-molded disposable cartridge includes features such as reaction chambers, a waste chamber, and chan- nels to direct the movement of fl uids. Integrated into the base cartridge are lance devices for the reagent blister packs, stirring devices, and lyophilized reagents. Reaction chambers and fl uid channels are covered with a clear layer of thermoplastic that is laser-welded to the base cartridge to form liquid-tight features. Th e reagent blister packs, thermal transfer pads, and hydropho- bic/oleophobic vents are then attached to complete the cartridge. To execute the biochemistry, there Detection chip Amplification chamber C D Sample input Blister packs with reagents Figure 3. Portrait cartridge and PA5000 analyzer spotted capture probes and is bonded into the cartridge detection chamber. Up to 8 × 8 arrays of nucleic acid probes can be applied to the chip sur- face using a noncontact print head. epitaxial silicon chip with Instrument are two chambers for sample prep, an amplifi cation chamber, a detection chamber, and a waste chamber that collects all liquid used in the assay. Th ree of the blister packs are avail- able for sample prep. Th e device is very fl exible for sample prep because of the presence of magnetizing and mixing capabilities, permitting mul- tiple extraction approaches including enzymatic, heat, and shearing as well as dilution, fi ltration, or magnetic par- ticle approaches to cell or nucleic acid capture. Th e amplifi cation chamber is designed for precise temperature control by using conduction heaters located above and below the chamber. Th e cartridge design includes thermal pads to optimize thermal conductiv- ity. Th e detection chip consists of a ~7-mm2 Th e instrument is controlled by a low-cost PC-based laptop computer. Great Basin's proprietary Portrait PA5000 analyzer application is installed on the laptop and controls the device through a single USB 2.0 connection. To minimize laboratory space requirements, the instrument dimensions are 6.5 × 21 × 17 in. Th e Portrait PA5000 analyzer comprises three primary subsystems: reagent fl ow control (valve motor drives, optical sensor), thermal control, and the opti- cal imaging system. Once the operator 20 IVD TECHNOLOGY | NOVEMBER/DECEMBER 2012 To execute an assay, a loaded cartridge is placed into an opened door. Once the door is closed, the cartridge is moti- vated into the instrument, where it is secured on a platform allowing access to the cartridge from above and below. Beneath the cartridge reside valve actuators, which can serve to control fl uidic movement, and lance actuators, which lance blister packs. Above the cartridge reside mix motors and step- per motors, which can fl atten blister packs and drive reagent into fl uidic channels. Th e mesofl uidic movements are achieved by compressing the blister packs or pressing on the diaphragm of the processing chambers with a motor and foot assembly. Compres- sion valves are used to isolate regions of the cartridge for mixing, amplifi ca- tion, and detection. Optical sensors located adjacent to the fl uid paths in the cartridge are used to determine fl uid movement and endpoints for chamber-fi lling activities. Multiple resistive heaters with thermocouple feedback are used to control tempera- ture for extraction, amplifi cation, and hybridization processes. Active stirring of the solutions is achieved by using magnetically coupled stir bars in the appropriate chambers. For isothermal DNA amplifi cation, the chamber is fl uidically isolated and maintained at 65° ±2°C by direct contact with a controlled heat source. For detection, the amplifi ed sample is diluted with hybridization buff er and introduced into a chamber where the modifi ed silicon chip is affi xed. As with prior steps, fl uidic movements and tempera- ture are controlled for the hybridiza- tion, washing, and signal development steps. Th e resulting visible features are inserts the cartridge into the Portrait PA5000 analyzer, enters required patient infor- mation, and initiates the assay sequence, the device performs the extraction sample dilution, amplifi cation, and detect step automatically and displays the result on the user interface and generates a report. ivdtechnology.com

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