Mother Nature has been the most inspiring source in the history of mankind. Human beings have been trying to learn to mimic nature’s designs to develop application for either solving problems in day to day life or improving their existing systems.
The term “Biomimetics” is very vast and the applications using biomimicry are in several fields starting from aeronautics to earth sciences to medicine to zoology. Trying to mimic the bird we have developed supersonic jets; from the ultrasound waves of mosquitoes and bats we have developed Radars and Ultrasound machines; studying the Eye has helped us develop cameras and still such designs by nature keep us further improve our products and technology. The bumps on the leading edges of Humpback whale and fingerlike primary feathers of raptors are teaching us to make the airplane wings suite far more agile flight with better fuel efficiency whereas the tiny serrations on a mosquito’s proboscis have inspired a team of Japanese scientists to make relatively painless hypodermic needle edges.
In the field of medicine, such biomimicry have been reported since the days of Emperor Nero in the First century AD. Nero who was shortsighted used an Emerald to magnify things for a better vision which is said to have been learnt from the dew drops, that depending upon the shape, act as magnifying glasses. Though exact inspiration is unclear, 200 years ago, brass trumpets with rubber bass were used to amplify the sound to mimic the middle ear components to assist those who have hearing impairment. Today we have electrically active devices such as pacemakers that mimic the impulses of the SA node of the heart to make an otherwise failing heart, beat and deep brain stimulators that mimic the electric current which are otherwise created by the chemical activity of neurotransmitters of certain cells, used in treating Parkinson’s disease.
Nichi-In`s work in this field has been with the biomimicry of the physiological milieu or niche, using physical characteristics and chemical materials in vitro, to study, characterize and compare various types of stem cells and to take those cells for a clinical application.
The Nichi-In Classification of Biomimetics in medicine:
I. Externally worn Biomimetic devices
1. Devices that augment the function of sensory organs:
(i) Hearing aid – Mimics the work of middle ear components
(ii) Spectacles – Mimics the cornea and corrects its focal point
II. Implantable (in vivo) Biomimetic devices
1. Simple physical filling/replacing devices
(i) Silicon and similar filling agents in cosmetology- mimic collagen, fat etc that otherwise fill a portion of the body to give a contour
(ii) The dentures, dental implants- mimic human teeth or its portions
(iii) Artificial limb prosthesis- mimic the lost limbs assist in ambulation to an extent
2. Mechanically active devices
(i) Artificial joint prosthesis- mimic the joints between bones
(ii) Cerebro-peritoneal shunts- mimic fluid movement systems across gradients
(iii) Mechanical -artificial heart valves
3. Biologically interacting synthetic implantable devices
(i)Artificial vascular prosthesis- mimic the arteries that act as conduit for the blood inside the body and made in such a way that over a period, a portion of the wall of this prosthesis is coated with cells such as fibroblasts.
4.Biologically derived implantable devices
(i) Bioprosthetic heart valves: Are made from materials derived from animal and human origin, decellularised and used in human patients, mimic the natural heart valve.
5. Electrically active devices
(i) Pacemaker- mimic certain specialized tissue in the heart (SA node, AV node etc) that create an electrical impulse periodically enable the heart, beat
(ii) Bionic ear (or) cochlear implant- mimic the inner ear hair cell produced nueral-electrical impulse thereby augmenting the hearing process
(iii) Deep brain stimulator- mimic the function of neurotransmitters
(iv) Bionic eye/retinal chip- mimic the retinal conversion of photo images to neural impulses that can be percepted by the brain
6. Hybrid implantable devices & systems
(i) Artificial heart assist device- functionally mimic the ventricular chamber of the heart and help with effectively pump the blood when heart fails. Has a surface coated with properties closet to the vascular endothelium and run by a battery outside the body
(i) Biological materials:
Animal serum, growth factors, hormones and other organism derived vaccines
(ii) Synthetic materials:
Chemical molecules that mimic the naturally existing compounds
(iii) Mixed components
Recombinant proteins with some biological derived components in it
(iv) Hybrid systems
These are the latest drugs with central portion of nano-particle mixed drug component coated with a layer outside similar to the cellular membrane. Eg. Doxil
(iv) In vitro Biomimetic materials and technologies
These are systems and material that try mimic outside the body in a laboratory culture dish, a milieu that’s in a biological system
1. Biological materials:
Animal serum, growth factors and biological feeder layers, amniotic membrane etc which sustain cells cultured in vitro by giving adequate nutrition to the cells
2. Synthetic materials:
These include nano-coated surfaces, adherent surfaces to allow growth of specific cells, three dimensional cultures using synthetic scaffolds
3. Mixed components
In vitro cultured cells using synthetic scaffolds mixed with biologically derived carriers for clinical application. Eg. Invitro grown chondrocytes used with bovine collagen, PGLA scaffold grown cells implanted together
4. Hybrid systems
Components from multiple sources including both biological and non-biological, are cultured, co-cultured, tissue engineered and made suitable for implantation into the body. Eg. Tissue engineered bladder, Tissue engineered trachea
The biologists look the “Cell” as a living thing with several parameters governing it or expressed or possessed by it such as CD markers, genomes, proteomes, signal pathways etc, most of which are yet to be made known in detail. But the physicists, chemists and specialist other than biologists working on, or in close association with the “cell”, see it, as a matter that can be manipulated based on the manipulation of the surrounding environments by changing the physical and chemical characteristics
NCRM has been involved in this work of creating a Biomimetic environment in the laboratory systems without biological components, to give the cells a milieu or niche that allow them to grow either in an undifferentiated manner or in a specific lineage. By this, the biological materials which possess a serious concern of unknown viruses or prion related contamination could be avoided thereby equipping the physicians working in regenerative medicine arena with safer cells/stem cells. We have been successful with (i) in vitro expansion of corneal limbal stem cells, (ii) transportation of corneal endothelial precursors, (iii) in vitro expansion of human bone marrow derived hematopoietic stem cells using such Biomimetic environments created by synthetic materials. These outcomes have significant potential for many clinical applications in regenerative medicine.
Inspired by organisms that live at high altitudes and certain pathogens which become more virulent at zero gravity, our next research proposal is to study the effects of gravity-less environment to evaluate and confirm its effects on the aging process of cells.
* This write-up on biomimetics was the base for the abstract of a talk given by Dr Samuel JK Abraham, Direcor, NCRM in the Bio-Asia meeting at Hydrabad, India in Feb 2010