Biosenors and Biochips

Couple of weeks back I went to my doctor for my annual exam, waited for a while flipping through magazine while sitting in my gown thinking of all the hings that could have gone wrong in past one year. Is it possible that bottles of red wine that I downed over past year may have actually strengthened my heart, opened up my arteries and made me healthier? Or the positive impact of red wine got neutralized by my slacking off from regular exercise. I took relief in the fact that turmeric that my wife dutifully put in almost every dish she prepares must have provided me enough curcumin and its benefit of anti-inflammatory, antioxidant, and anti-cancer properties. But wait, was it enough to neutralize the cancer causing poisons in water bottles, car exhaust, carpet dust, paints and  I can go on and on. I should better start eating a spoon of turmeric every day, start downing reservitol tablets instead of red wine, cinnamon sticks may be!

Luckily for me, doctor walked in waking me up from my day dreaming. He went through routine questions and asked me to give some blood for routine testing. I clenched my teeth, squeezed my eyes and went through blood draw. Nurse curtly told me that if there is something really bad doctor will call me or I should wait for couple of weeks and my results will be mailed to me.

Now, being a Star Trekky I wish if only McCoy can wave his tricorder tell me about everything there is to know and save me two weeks of not knowing if I am going to drop dead or not. Although Tricorder will take some time to appear, researchers are taking baby steps to reach that goal and one way to approach is using miniature sensing devices especially Biosensors or Biochips. Biosensors in simple terms are stand alone miniature portable devices that can detect range of analytes quickly and can play significant role in medicine, agriculture, environmental monitoring, food testing and homeland security among others. Biosensors combine biological elements for specific and sensitive detection of analyte with transduction technology to convert biological recognition event into an easily measurable signal preferably electrical.      

I started my long journey in biosensing way back in early 1990s from book by Anthony P. F. Turner where biosensors are defined as biological element in intimate contact with a transducer. Biological element can be cells, enzymes, proteins, antibodies, nucleic acids and are used as recognition element for a specific analyte of interest. Transducers convert the signal arising from specific interaction between biological element and analyte into an easily measurable and meaningful signal. Typical signal coming from biological interactions can be mass change, optical, thermal or electrical that is then converted by a transducer into easily readable results. The most common and commercially successful example of a biosensor is a glucose sensor available in any pharmacy and uses Glucose oxidase enzyme to oxidize glucose and use the resulting electron to generate current proportional to the amount of glucose.

Biosensors are ideally suited for range of applications from environmental monitoring, food testing, clinical diagnosis, biodefense, cellular analysis etc. In light of September 11th, 2001 attack there was renewed interest in development of portable biosensors for detection of biological pathogens, explosive and radioactive materials.  

Things have changed in past 15years or so. Nanotechnology has matured, bringing new detection methods for biosensing. Really small gold and silver nanoparticles change color in response to biological events. Quantum dots can enhance optical signals. Nano-barcodes and carboon nanotubes are other examples of novel detection tools for bilogical applications.  Microfluidics enables several analytes from minute amount of samples and small and inexpensive cameras means detection can be done anywhere and anytime. Deep penetration of cell phones means that can possibly be used as readouts for biosensors even in inaccessible part of the worlds bringing biosensors to masses. In addition to diagnostics, environmental or other type of macroworld measurements, biosensors have gone micro or even nano. Small changes in physico-chemical-biological events inside the cells can be measured using protein based biosensors. Hence there is a need to redefine biosensors by de-linking biological elements from transducer. To redefine Biosensors is easier said then done. If it is broaden too much it looses its focus and narrowing it too much excludes several unique biosensing methods. Need more time!   

But challenges remain. Despite impressive research work, only true biosensor for diagnosis that is commercially available off the shelf in pharmacy is glucose sensor. Pregnancy dipsticks can be considered another example even though purist will exclude it calling it a dipstick technology. But I say you one can write a simple iPhone App that will allow a picture to be taken of the pink band and can quantitate it to tell how far pregnancy has progressed. Other promising applications have lagged and I wonder why! That is a reason for starting this blog.

I want to sample research in Biochips and Biosensors and provide my 2cents worth of opinion on the usefulness of the technology. Enjoy and leave feedback!

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