Course on Electrochemical nano-bio-sensing and Bio/CMOS interfaces 13. CMOS architectures for Bio-Sensing

Transcription

1 Course on Electrochemical nano-bio-sensing and Bio/CMOS interfaces 13. CMOS architectures for Bio-Sensing 1

2 Detection Architecture Voltage Follower Analog Adder Analog Shifter Current Amplifier Analog MUX Analog Integrator S.Carrara, EPFL - Lausanne 2

3 CMOS architectures for VLSI in DNA Detection 3

4 CMOS architectures for VLSI in Metabolites Detection 4

5 Detection Architecture V = Vo W R C A I = I(w-c) S.Carrara, EPFL - Lausanne 5

6 Detection Architecture I = 0 V = Vo Voltage Follower W R C Iw Current Amplifier S.Carrara, EPFL - Lausanne 6

7 The basic of Op. Amp. - + VOLTAGE FOLLOWER R Vin + W C TRANSIMPEDANCE AMPLIFIER - S.Carrara, EPFL - Lausanne 7

8 Introduction Potential Control Configuration GROUNDED COUNTER ELECTRODE Operational amplifier features: small bias current ( < pa) high input impedance ( > GΩ) high voltage gain ( > 104) low input offset voltage ( < 10 mv) accuracy stability (wide bandwidth) K.Iniewski. VLSI Circuits for biomedical applications. Artech House, pp Disadvantages: Many components (vulnerable to parameters mismatching) Cork July 12-17, 2009 GROUNDED COUNTER 8 Cristina Boero

9 Ground I = 0 V = Vo Voltage Follower W R C Iw Current Amplifier S.Carrara, EPFL - Lausanne 9

10 Introduction Current Measurement using a TRANSIMPEDANCE AMPLIFIER Advantages: small current can be measured by switching R m both potential and current are referred to ground K.Iniewski. VLSI Circuits for biomedical applications. Artech House, pp GROUNDED WORKING Cork July 12-17, Cristina Boero

11 Ground I = 0 V = Vo Voltage Follower W R C Iw Current Amplifier S.Carrara, EPFL - Lausanne 11

12 Applications in Drugs Monitoring P450 TARGETS CYP cytochromes 2C9 2D6 Drugs priciples Hypoglicemic agents, Angiotensin Blockers, Beta blockers Endogenous metabolic molecuels 2B4 Anti-obesity 3A4,5,7 3B6 HMG CoA Reductase Hinibitors, Anti-arrithmics, Calcium channels blockers Anti-neoplastic agents Anti-neoplastic agents 2C8 Anti-neoplastic agents 4A11 Arachidonic acid 11A1 Cholesterole 3A43 testosterone 12

13 Problem of multi-panel arrays response S1 S1 S1 S2 S1* S1* S1* S2* E1 E2 E3 E3 Bio-sensor Voltammogram Plot Intelligence 13

14 Peak signature from each single Drug D1 D2 D3 It is then possible to distinguish each single drug contribution from peaks in the Voltammogram 14

15 Peaks signature from each single Drug DX300 CP500 - fitting improvement (D) Current (ua) DX CP CP DX Potential (mv) Multiple detection of Cyclophosphamide (CP) and Dextrometorphane (DX) by using P450 3A4 15

16 The Heterotropic Kinetics HETERO ACTIVATION D2 D1 The presence of D2 activates The detection on D1 D2 D1 PARTIAL INHIBITION The presence of D2 inhibits The detection on D1 16

17 Multiple drugs detection: CYP3A4 Inhibition of CP detection CP DX Different amounts of CP and DX result in two very-well defined peaks once detected by P450 3A4 17

18 Multiple drugs detection: CYP2C CYP2C9 + Flurbiprofen 200 M Peak variation upon naproxen addiction Current (A) Activation of FL detection naproxen 0 um naproxen 200 um naproxen 300 um naproxen 400 um naproxen 500 um NP FL Potential vs Ag/AgCl (mv) Naproxen (NP) and Flurbiprofen (FL) also result in two very-well defined peaks once detected by P450 2C9 18

19 Peaks Amplitude is affected by the presence of other drugs Dependence from the other drug concentrations Charging current Faradic currents The Gaussian decomposition in cytochrome P450 based detection has to account for heterotropic kinetics 19

20 Detection Architecture? - + VOLTAGE FOLLOWER R Vin + W C TRANSIMPEDANCE AMPLIFIER - S.Carrara, EPFL - Lausanne 20

21 Input Signal Generation f(t) A I(τ ) T = f ( t) dt = A f(t) t 0 A2 t I(τ ) = T f ( t) dt = A2 > 0 A S.Carrara, EPFL - Lausanne 21

22 Input Signal Generation I (τ ) = f ( t) dt = f (t) t f (t) t = t t S.Carrara, EPFL - Lausanne 22

23 23

24 CMOS front-end demands 1. Precise Current measurements 2. Multiplexing for different molecules 3. Reliability in Temperature 4. Reliability in ph 5. Multiplexing Molecular Detection with T and ph 24

25 1. Precise Current measurements Current-to-frequency converter 25

26 2. Multiplexing for different molecules Different working electrodes are multiplexed to the current-to-frequency converter 26

27 3. Reliability in Temperature 27

28 3. Reliability in Temperature For VLSI, FET Transistor based circuits are more suitable than BJT 28

29 4. Reliability in ph In CV, The peak position is ph dependant 29

30 4. Reliability in ph The Ion-Sensitive FET measure the solution ph 30

31 5. Multiplexing Molecular detection with T and ph The switches also multiplex the T and ph measure 31

32 CMOS architectures for VLSI in DNA Detection 32

33 Electrochemical Interface AVERAGE IONS POSITION Ion planes are formed at the interface when electrodes immersed in solution are polarized 33

34 Electrochemical Interface IONS DISPLACEMENT New IONS POSITION Previous IONS POSITION Ion planes are formed at the interface when electrodes immersed in solution are polarized 34

35 The DNA Detection Principle R ct Applied voltage (e.g. V<0) DNA molecules ELECTRODE C dl C R S A d ELECTRODE Ions displacement Unlabeled ssdna may be detected with capacitance measurements as due to charge displacement 35

36 Current Based Capacitance Measurement (CBCM) I AVG i( t) = I i ( t) = I dc 2 + dc + 1 T / 2 0 C Frequency! T i C ( t) dt I I = 2 dc AVG + CV step THE CAPACITANCE! f Method for a precise Capacitance measurement 36

37 CMOS for CBCM detection The circuit assures the square signal generator, an inverters, and an integrator to calculate the average current 37

38 The Chip Electrodes Layout 38

39 The VLSI Implementation of the Chip (CBCM method) the Chip (CBCM method) (CBCM = Charge Base Capacitance Mode) 39

40 The problem of overlapping signals Ck and Ck_ signals need to be not-overlapping in order to assure the correct square signal generation 40

41 The circuit solution A simple logical circuit and a digital multiplexer assures not-overlapping Ck and Ck_ signals 41

42 The Measurements Set-up The Chip has been mounted onto a PCB for PC remote control and testing 42

43 Liquid Measurement set-up Chip is glued on a PCB Fluidic cell Output PCB pads Bonding wires Two different Chambers 1mmX1mm 43

44 DNA detection in CBCM mode Large differences in C values The chip-by-chip reproducibility has been not so high: the problem is on the chip electrodes cleaning 44

45 DNA detection in CBCM mode Large Standard deviation The reproducibility on the same chip-spot is not so high: here the problem is on the nanoscale aperture in the probes surfaces 45

46 Capacitance vs Frequency The trends of the measured capacitance vs frequency decrease the accuracy of the measurements in CBCM mode 46

47 Frequency to Capacitance Measurement (FTCM) Principle: Frequency To Capacitance Mode V A V out I ref V B V ref V A -V B =V ref V A -V B = -V ref V ref V out T T=f(C)? t t Linear behavior 47

48 T 2RC Current Based Capacitance Measurement (CBCM) t V = RC c( t) Vch arge 1 e T c( ) Vref = Vch arge 1 e 2 T T ( ) = V = RC ref RIref 1 e 2 V ref V ln 1 T = 2RC ln 1 RI RI 2 Vc = ref T = 2 V RC ref ref 1 Method for a precise Capacitance measurement 48

49 49 Method for a precise Capacitance measurement Method for a precise Capacitance measurement The Taylor Series The Taylor Series (3) ) ( ) ( (0) ) ( o x x x f x x x f f x f = ( ) { } x o x x = 1 (2) [ ] [ ] x o x x = ln 1 (2) ln ln x o x + + = ) (2 0

50 Current Based Capacitance Measurement (CBCM) T 2RC ln 1 V = ref RI ref 1 T = 2RC ln 1 1 V RI ref ref 2RC ln 1 + V RI ref ref 2CV I ref ref Method for a precise Capacitance measurement 50

51 Frequency to Capacitance Measurement (FTCM) Principle: Frequency To Capacitance Mode V A V out I ref V B V ref V A -V B =V ref V A -V B = -V ref V ref t V out T = 2RC ln 1-1 V I REF REF R T V REF /I REF R 0 Linear behavior t 51

52 Electrodes Layout 52

53 Chip Architecture (FTCM) 53

54 Measurements Set-up 54

55 Validation Test A test structure has been implemented on chip beside the array to characterize the measurement circuit with discrete test capacitances (10 pf -10 nf) Slope = Intercept = 62 pf σ < 0,3 % Offset is due to parasitic capacitances of cables Meas_CAP (nf) uA 5.18uA 2.49uA Nom_CAP (nf) 55

56 Probes property on FTCM mode Rp decreasing The linearity between the current and the measured frequency is lost at low current if the CMOS/Bio interface is not a perfect capacitor 56

57 Liquid Measurement set-up 57

58 DNA detection in FTCM mode Time stability on the single chip-spot is pour due to nano-scale aperture in the probes surfaces 58

59 DNA detection in FTCM mode In chip spot-by-spot reproducibility is improved due to better cleaning of the spot gold electrodes 59

60 Summary Different detections may be developed to sense different bio-molecules Different modes may be implemented to obtain similar detection on the same bio-molecule VLSI bio-chip development are possible based on quite simple analog building blocks CMOS ASICs are required to be specialized for each single Bio-Sensing Application 60

61 Exercise 1. To design a simple CMOS circuit enabling the detection of the benzphetamine by means of the Cytochrome P450 2B4 powered by carbon nanotubes by using an electrochemical cell with two working electrodes: : the first is for the biodetection and the second is to measure the capacitive current obtained from carbon nanotubes. The final detection signal has to be the difference of the currents from these two working electrodes 61