We report automated DNA sequencing in 16-channel microchips. A microchip prefilled with sieving matrix is aligned on a heating plate affixed to a movable platform. Samples are loaded into sample reservoirs by using an eight-tip pipetting device, and the chip is docked with an array of electrodes in the focal plane of a four-color scanning detection system. Under computer control, high voltage is applied to the appropriate reservoirs in a programmed sequence that injects and separates the DNA samples. An integrated fourcolor confocal fluorescent detector automatically scans all 16 channels. The system routinely yields more than 450 bases in 15 min in all 16 channels. In the best case using an automated base-calling program, 543 bases have been called at an accuracy of >99%. Separations, including automated chip loading and sample injection, normally are completed in less than 18 min. The advantages of DNA sequencing on capillary electrophoresis chips include uniform signal intensity and tolerance of high DNA template concentration. To understand the fundamentals of these unique features we developed a theoretical treatment of cross-channel chip injection that we call the differential concentration effect. We present experimental evidence consistent with the predictions of the theory.

Self-poisoning is a common reason for acute presentation to hospital. Commonly involved drugs have been reported, but few data exist concerning the different combinations of agents or comparative doses ingested. The present study sought to better characterise the typical patterns of drug overdose that may present via the emergency department. Consecutive adults 16 years of age that presented to York Hospital owing to self-poisoning were studied for 2010-2011 inclusive. The primary outcome measure was reported dose, expressed as a multiple of the defined daily dose (DDD) to allow comparison between different agents. There were 1024 patients, including 622 women (60.7%), and median age was 32 years (range, 16 to 92 years). Overdose in men was associated with a higher overall quantity of drugs: arithmetic mean of 20 DDD multiples (95% CI, 15-26) versus 13 (11-15), p = 0.001. Overdose involved a single agent only in 538 patients (52.5%). The mean paracetamol dose was 4.0 (95% CI, 3.7-4.3) DDD multiples; the doses of antidepressants (19.4, 17.0-21.7, p < 0.0001) and benzodiazepines (18.0, 12.8-23.2, p < 0.0001) were comparatively higher. The types of agents involved in self-poisoning and common combinations of agents are characterised. Psychotropic medications were ingested in comparatively larger quantities than analgesic agents and had worse clinical outcome. Further work is required to understand the factors that determine the quantity of drug ingested in patients at risk of drug overdose so as to minimise the risk of significant toxicity.

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