Lab-on-a-Chip Technology, as a Remote Distributed Format for Disease Analysis: Professor Jon Cooper, University of Glasgow

Previously, Lab-on-a-Chip technologies have exploited many aspects of microsystems technology, including sensor miniaturisation and microfluidics, in order to deliver a variety of applications, particularly those associated with DNA analysis, proteomics and diagnostics. Despite the numerous analytical advantages that are delivered as a consequence of device miniaturisation, the vast majority of all devices that have been proposed either as commercial instruments or as research projects, have required to be based on a laboratory bench. In contrast, Lab-on-a-Pill technology now has the proven ability to deliver both remote and-or distributed analysis, resulting in a wide range of potential applications, including those associated with biomedical analysis in the gastro-intestinal tract, process control in industry and the functional foods industry. Lab-on-a-Pill: The International Context of the Work: The invention of the transistor enabled the implementation of the first radiotelemetry ingestible capsules, which utilised simple circuits for in vivo telemetric studies of the gastro-intestinal (GI) tract [1]. These units could only transmit from a single sensor channel, and were difficult to assemble due to the use of discrete components [2]. The measurement parameters consisted of either temperature, pH or pressure. These first attempts of conducting real time non-invasive physiological measurements (understandably, given the extent of technology in 1957) suffered from poor reliability, low sensitivity and short lifetimes of the devices. Despite this, the first successful pH gut profiles were achieved in 1972 [3], with subsequent improvements in sensitivity and lifetime [4, 5]. Single channel radiotelemetry capsules have since found limited applications for the detection of disease and abnormalities in the GI tract [6-8] where restricted access prevents the use of traditional endoscopy [9]. Most radiotelemetry capsules utilise laboratory type sensors such as glass pH electrodes, resistance thermometers [10] or moving inductive coils as pressure transducers [11]. However, the relatively large size of these sensors limits the functional complexity of the pill for a given size of capsule.

The concept of remote and distributed miniaturised sensing has been most dramatically exemplified by the camera-on-a-pill technology, associated with video endoscopy within the gastro-instestinal tract [9]. The important contrast between this seminal work in video imaging (e.g. that produced by IMC, Korea and Given Imaging), and of our own work is that whilst the camera-on-a-pill seeks to create a visual image of the remote area being sensed, we wish to develop a remote chemical image of that site Name of Manufacturer Mackay/Jacobson, Nature, 179, 1239-40 (1957) HC Noiler, Telefunken, Germany (1965) M2A, Given Imaging, Israel (2001) Norika 3, RF System Lab , Japan (2002) Technology Endoradiosonde, Single transistor Heidelberg pH capsule Video Capsule CMOS camera Main Technical Specifications Battery, single channel (9x28 mm) Battery, single pH sensor (8x20 mm) Battery, 2 frames/s, 6 hour lifetime (11x26 mm) Induction, 30 frames/s, drug, prop, tracking, sampling (9x23 mm Battery, camera, drug release actuator, ultrasound (10x30 mm). Battery, ASIC, m-sensor, program, 40 hour lifetime (16 x 55 mm). Comparison

Temperature or pressure Wireless communicatio Small, utilised in medical research Video imaging (single channel) Video imaging, multiple function, excl. battery

Video Capsule, CCD camer

IMP, IMC, KIST Korea (1999-2009)

Endoscopic Microcapsule

Evolutionary. Contract negotiation with GU

IDEAS, Glasgow Uni. UK (2001-2004)

Microelectronic pill Chemical imagin

Sensor & system integr. multi capsule protocol.

Current Activity at the University of Glasgow: Our current research on sensor integration and onboard data processing has focused on the development of microsystems capable of performing simultaneous multiparameter physiological analysis both in vivo and in vitro. The technology has a range of applications in the detection of disease and abnormalities in medical research. Our overall aim has been to deliver enhanced sensor functionality, reduced size and low power consumption, through system level integration on a common integrated circuit platform comprising sensors, analogue and digital signal processing, and signal transmission. We have therefore created a platform which comprises a novel analytical microsystem incorporating a four channel microsensor array for real time determination of temperature, pH, conductivity and oxygen (work pioneered by Professor Jon Cooper and Dr Erik Johanessen). The sensors have been fabricated using standard

photolithographic pattern integration, and are controlled using a custom made application specificintegrated circuit (ASIC), designed in Glasgow (by Dr Dave Cumming and Dr Wang Li) and fabricated by Europractice. The ASIC samples the data with 10 bit resolution prior to communication off chip as a single interleaved data stream. An integrated radio transmitter sends the signal to a local receiver (base station), prior to data acquisition on a computer. A receiver allows remote control of the Labon-a-Pills function, switching sensors and-or power on and off, on demand The sensors comprise a silicon diode to measure the body core temperature, whilst also compensating for temperature induced signal changes in the other sensors; an ion selective field effect transistor, ISFET to measure pH; a pair of direct contact gold electrodes to measure conductivity; and a three-electrode electrochemical cell, to detect the level of dissolved oxygen in solution. All of these measurements will, in the future, be used to perform in vivo physiological analysis of the GI-tract. These four sensors (pH, s, T, pO2) not only provide useful information for applications in industry and biomedicine per se, but also are a platform that will enable greater sensor functionality to be created (e.g. the electrochemical oxygen sensor could be readily modified in order to develop a sensor interface for the implementation of immunoassay technology). We have now presented real time wireless data transmission from a model in vitro experimental setup, for the first time, and are currently working with the Veterinary School at the University of Glasgow on performing multi-channel in vivo experiments. Extensive literature searching has revealed that we are the only group world-wide working at this state of the art in multi-channel remote wireless sensing (e.g. there is already a class of oesophageal pH sensors that are available in clinical practice). There has also recently been serious interest from two multinational electronics companies in obtaining IP generated through this work. References: 1. S. Mackay and B. Jacobson, "Endoradiosonde," Nature, vol. 179, pp. 1239-1240, 1957. 2. H. S. Wolff, "The radio pill," New Scientist, vol 12, pp. 419-421, 1961. 3. S. J. Meldrum, B. W. Watson, H. C. Riddle, R. L. Bown and G.E. Sladen, "pH Profile of gut as measured by radiotelemetry capsule," Brit. Med. Journal, vol 2, pp. 104-106, 1972.4. D. F. Evans, G. Pye, R. Bramley, A. G. Clark, T. J. Dyson and J. D. Hardcastle, "Measurement of gastrointestinal pH profiles in normal ambulant human subjects," Gut, vol. 29, no. 8, pp. 1035-1041, Aug. 1988. 5. R. H. Colson, B. W. Watson, P. D. Fairlclough, J. A. Walker-Smith, C. A. Campell, D.

Bellamy and S. M. Hinsull, "An accurate, long-term, pH sensitive radio pill for ingestion and implantation," Biotelem. Pat. Mon., vol. 8, no. 4, pp. 213-227, 1981. 6. S. S. Kadirkamanathan, E. Yazaki, D. F. Evans, C. C. Hepworth, F. Gong and C. P. Swain, "An ambulant porcine model of acid reflux used to evaluate endoscopic gastroplasty," Gut, vol. 44, no. 6, pp. 782-788, June 1999. 7. A. G. Press, I. A. Hauptmann, L. Hauptmann, B. Fuchs, K. Ewe and G. Ramadori, "Gastrointestinal pH profiles in patients with inflammatory bowel disease," Aliment Pharm. Therap., vol. 12, no. 7, pp. 673-678, Jul. 1998. 8. G. Pye, D. F. Evans, S. Ledingham and J. D. Hardcastle, "Gastrointestinal intraluminal pH in normal subjects and those with colorectal adenoma or carcinoma," Gut, vol. 31, no. 12, pp. 1355-1357, Dec. 1990. 9. G. Iddan, G. Meron, A. Glukhovsky and P. Swain, "Wireless capsule endoscopy," Nature, vol. 405, no. 6785, pp. 417, May 2000. 10. G. X. Zhou, "Swallowable or implantable body temperature telemeter - Body temperature radio pill," in Proc. IEEE Fifteenth Ann. Northeast Bioeng. Conference, Boston, MA, 1989, pp. 165-166. 11. S. Mackay, "Radio telemetering from within the body," Science, vol. 134, pp. 1196-1202,

Telemetering from within the body using a pressure-sensitive radio pill B. W. WATSON, B. ROSS, AND A. W. KAY
From the Regional Medical Physics Department and the University Department of Surgery, Royal Infirmary, Sheffield It has been an aim of the clinical physiologist to be able to measure continuously such physiological

variables as pressure, temperature, and hydrogen ion concentration under conditions of minimal disturbance to the subject or his environment. The development of miniature electronic components, such as the transistor, has made it possible to construct transducers and amplifiers within such a small space that studies can be undertaken in hitherto inaccessible parts of the human body. A radio transmitter with a total volume of approximately 2 cc. which can transmit information from the inside of the body was described in 1957 (Mackay and Jacobson, 1957). These devices have been further developed and they have been used mainly to investigate the gastrointestinal tract. Telemetering capsules ('radio pills') capable of recording pressure, temperature, and pH have been produced and a review of these devices is given elsewhere (Mackay, 1959, 1961; Jacobson, 1960; Wolff, 1961). They transmit a frequency modulated signal in the frequency range 300 Kc/s to 10 Mc/s. The pressure pill modifications described in this paper enable the construction of a simple, reliable and inexpensive device. SPECIFICATION 1 The device should be as small as possible and not greater than 3 cm. long by 1 cm. diameter. 2 The battery must be replaceable. Available pills in Great Britain permit of single studies only. 3 The transmissions should continue for not less than 50 hours. 4 The response to pressure should be linear. 5 It must possess a sensitivity which can be adjusted

from 50 cm. water to 300 cm. water full-scale deflection on the recorder. 6 The temperature stability should be such that the pressure measured is accurate to 10 % over the range of 95F. to 105F. 7 The frequency on which the pill transmits should be variable so that two or more pills can be used synchronously in one subject. 8 The characteristics of the diaphragm should not be affected by the body fluids encountered by the capsule. 9 The design should be flexible so that parameters other than pressure can be measured without necessitating major basic modifications of the capsule. The pills described so far have fallen short of these ideal requirements in one or more respects. All circuits use the variation in inductance. Pressure variations on a rubber or perspex diaphragm or a metal bellows cause movement of a ferrite core or disc which modifies an inductance in the circuit. Both rubber and perspex are affected by water and body fluids. To overcome this, silicone grease (Connell and Rowlands, 1960) or a silicone fluid seal is necessary between the diaphragm and the body fluids. Even when these precautions are taken, and a special rubber has been developed for this purpose (Jacobson, 1960), long-term changes still occur. The ferrite pot core (Rowlands and Wolff, 1960) seemed to offer the possibility of using a metal diaphragm. The inductance depends on the air gap between this disc and the core, variations in the gap causing a change in the inductance (L), and this in turn leads to a change in frequency of oscillations. The carrier frequency is in

the band 300 to 500 Kc/s and the modulation caused by a positive pressure is such as to decrease the frequency by approximately 20 Kc/s. The components are wired into a perspex former and sealed into the perspex body before the diaphragm assembly is undertaken. The mechanical layout is shown in Fig. 2. The body of the pill is machined from i in. diameter perspex rod. The metal diaphragm is a silver-plated 1 thou. thick copper disc 7-5 mm. in diameter. This rests on a shoulder machined into the perspex body. A brass spigot tapped the electronic components, so ensuring a rigid assembly and a good seal. If a slight leak still remains, silicone grease can be used in the battery end. In preliminary work, adhesives were used to attach the PRESSURE [cm.Hg] FIG. 4. Pressure characteristics. metal diaphragm but this had three disadvantages: first, a good seal between metal and perspex was difficult to obtain; secondly, spreading of the adhesive affected the properties of the disc; thirdly, it is necessary to be able to replace the diaphragm assembly quickly because damage can occur during recovery from the body or during the cleaning process which is necessary before the capsule is used in another clinical experiment. The completed pill together with the diaphragm assembly is shown in Fig. 3. PRESSURE CHARACTERISTIC Typical pressure curves are shown in Fig. 4. The maximum

sensitivity is 50 cm. H2O. Higher sensitivities can be achieved but stability considerations make it impractical. The error due to non-linearity is less than 5% of fullscale value. If it is required to measure pressures greater than 150 cm. H20 it is necessary to increase the thickness of the diaphragm in order to retain linearity. TEMPERATURE CHARACTERISTIC - Considerable care is needed in order to get a pill which is stable in a changing temperature environment. A temperaturesensitive reactance is not used in X/ the present circuit. Fortunately PILL the change in frequency due to M 8 component variations, particularly in the transistor, causes the frequency to decrease whereas the air which is contained within the pill expands with increase in temperature causing the frequency to increase; by adjusting the gap in the pot core it is usually possible to balance out the two effects. The differing temperature BATTERY VOLTAGEA FIG. 6. Frequency drift with change in battery voltage. -Q- 126 kcls/cm. Hg -E- 1J09 kc/s/cm. Hg

STABILITY frequency of the transmitter changes over the life of the pill, the base line of pressure measurements will drift. This is inconvenient for long-term studies of pressure changes and would preclude reliable analysis. Furthermore, frequency _ changes must be prevented if absolute pressure measurements are required. This effect may be due to a change in the circuit condition caused by variation in the battery voltage or to deterioration in the mechanical properties of the diaphragm. The Mallory cell type RM312 is used to power the pill. The cell has a stable voltage curve as the current is drained from it and regulation is within 0.5%. The voltage drops quickly from 1-35 volts to 1-32 volts over the first 30 minutes and then remains within the quoted regulation. The variation in frequency with battery voltage is shown in Fig. 6. It will be seen that, from battery changes alone, the pill is stable within the above period assuming that 30 minutes is allowed for the pill to stabilize after refuelling. The drift in I 5 base line during recordings from ingested pills corresponds to a change in the carrier frequency of less than 3%; FIG. 7. Radio receiver cireuit. .

On pills tested after recovery and refuelling, the pressure calibration has been found to be the same. the same frequency as that of the pill. The resulting audio signal is then amplified and counted on the rateFIG. 8. Radio receiver and recorder. meter. The ratemeter converts the 0 to 20 Kc/s audio signal into a 0 to 1 m.amp current which is recorded on a pen recorder. The receiver drifts less than + 1 Kc/s in 24 hours after an initial warm-up period of 30 minutes. The circuit will respond to 10 microvolts of signal at the input and the ratemeter is independent of signal strength from 10 microvolts to 100 millivolts. With this receiver it is possible to lose the signal if the pill is orientated in a critical position. In practice this happens rarely and if a clamp circuit holds the ratemeter until the signal returns the record is not seriously affected. The signal level can also be recorded but in our initial studies this has not been necessary. The clinical readings are made by adjusting the base line to 0-2 m.amps on the recording milliameter. If the signal is lost during the recording the needle returns to zero on the paper. The complete instrument together with the recorder is shown in Fig. 8. To date our clinical studies have been limited to the life of the pill (80 hours). The receiver described by Jacobson (1960) would seem to be the one of choice for studies over periods greater than three days. CLINICAL APPLICATION The telemetering capsule and the radio receiver described above have been used to study the effect of various abdominal operations on gastro-intestinal motility in

man. The capsule, previously sterilized by immersion in 0.5 % solution of hibitane in spirit for four hours, is inserted at the duodeno-jejunal flexure. Thus, without inconvenience to the patient, the pill can be monitored continuously from the end of the operation until the 185 Downloaded from gut.bmj.com on March 6, 2012 - Published by group.bmj.com186 Methods and techniques return of typical type 3 pressure waves is observed on the permanent record. The duration of small bowel paralysis after various operations, including resection of the vagus nerves to the stomach, has been determined and is soon to be reported. Changes in gastric motility are recorded by suturing a capsule to the gastric mucosa. The results of these studies have an important bearing on the postoperative management of patients undergoing gastrointestinal surgery. In some patients, recordings have been made simultaneously from the stomach and small intestine. This has been rendered feasible by the flexibility of the design of our telemetering device. In clinical experiments on the urinary bladder, the stability of our pill has permitted measurement of absolute pressures during postural changes, and recordings of intravesical pressure during normal micturition. CONCLUSIONS The pills described above have been shown capable of recording pressure changes over the period of the battery life (80 hours). The drifts in the recorder base line are small but these could be reduced considerably by improving the receiver. These improvements would seem to be essential if the

radio pill is to be used as a diagnostic technique in gastroenterology. The information collected over a period of three days is considerable, and some method of electrical recording such as magnetic tape is necessary in order that electronic analysis can be made. Collecting information from pills sutured in known parts of the intestine will aid this analysis. From our experience it is clear that economic considerations alone demand that the device be recoverable. Most clinical research projects require a large number of experiments and, furthermore, it is difficult to envisage adequate testing of a sealed device without loss of a large proportion of the useful life. In future developments a smaller device would seem to offer possibilities for studies in children but it is difficult to see how the present design could be reduced significantly. An externally energized pill would offer advantages if recordings over many months are envisaged and if it enabled the size to be reduced substantially. Recordings from dogs have been made by Jacobson and Lindberg (1960) over a period of three weeks and, using a larger battery, for as long as three months. We wish to express our thanks to Miss D. Wemm, Mr. H. Wood, and Mr. W. Dyson for technical assistance. Our thanks are also due to Mr. H. Wolff, of the Medical Research Council Bioengineering Laboratory, who has been responsible for much of the early developmental work on radio-telemetering in this country, for many

helpful discussions. Together with Solartron Electronics Ltd., Mr. Wolff developed the perspex diaphragm pill, experience with which has led to the modifications described. This work has been supported by the research funds of the United Sheffield Hospitals and the Sheffield Regional Hospital Board. REFERENCES Connell, A. M., and Rowlands, E. N. (1960). Wireless telemetering from the digestive tract. Gut, 1, 266-272. Jacobson, B. (1960). Development and use of endoradiosonde techniques. Progressive Report, Karolinska Institutet, Department of Medical Electronics. -, and Lindberg, B. (1960). F.M. receiving system for endoradiosonde techniques. IR.E. Transactions on Medical Electronics, October 1960, pp. 334-339. Mackay, R. S. (1959). Radio telemetering from within the human body. IR.E. Transactions on Medical Electronics, June 1959, pp. 100-105. (1961). Radio telemetering from within the body. Science, 134, 1196-1202. and Jacobson, B. (1957). Endoradiosonde. Nature (Lond.), 179, 1239-1240. Rowlands, E. N., and Wolff, H. S. (1960). The radio pill. Telemetering from the digestive tract. British Communications and Electronics, 7, 598-601. Wolff, H. S. (1961). 'The Radio Pill'. New Scientist, 12, 419-421