Respirocytes A Mechanical Artificial Red Cell: Exploratory Design in Medical Nanotechnology -Robert A. Freitas Jr. Presented by UmaMaheswari Ethirajan

Overview  Introduction  Preliminary Design Issues  Nanotechnological design of Respiratory Gas carriers  Baseline design  Therapeutics  Safety and Bio-compatibility  Applications  Summary and Conclusion

Introduction  Molecular manufacturing processes applications.  Medical implications – precise interventions at cellular and molecular levels.  Medical nanorobots – research, diagnoses and cure.  Preliminary design for artificial mechanical erythrocyte or Red Blood Cell (RBC) – Respirocyte.

Preliminary Design Issues  Biochemistry of respiratory gas transport – oxygen and carbon-dioxide.  Existing Artificial Respiratory Gas carriers Hemoglobin Formulations  50% more O 2 than natural RBCs.  Dissociates to dimers, Binds to O 2 more tightly, Hemoglobin oxidized. Fluorocarbon Emulsions  Physical solubilization – emulsions of droplets Shortcomings of Current technologies  Too short life time  Not designed for CO 2 transport  vasoconstriction

Design of Respiratory Gas carriers  Pressure Vessel Spherical, Flawless diamond or sapphire 1000atm – optimal gas molecule packing density Discharge time very less - <2 minutes  Recharging with O 2 from lungs Respiratory gas equilibrium – more CO 2  Provide additional tankage for CO 2  Means for gas loading and unloading

Molecular Sorting Rotors  Binding site pockets – rims – 12 arms  Selective binding  Eject – cam action  Fully reversible – load and unload  7nm x 14nm x 14nm  2 x kg  Sorts molecules of 20 or fewer atoms  10 6 molecules/ sec

Molecular Sorting Rotors (cont’d)  Power saving – generator subsystem  90% occupancy of rotor binding sites  Multi-stage cascade – virtually pure gases

SSorting Rotors binding sites O 2, CO 2, Water, Glucose DDevice Scaling On-board computer – 58nm diameter sphere 37.28% of tank surface – sorting rotors Reasonable range – 0.2 to 2 microns Present study assumes – approx. 1 micron BBuoyancy control Loading and unloading water ballast Very useful – exfusion from blood Example – specialized centrifugation apparatus Nanotechnological Design of Respiratory Gas carriers (cont’d)

Baseline Design - Power  glucose & oxygen – Mechanical Energy  Glucose – blood & Oxygen – onboard storage  Glucose Engine – 42nm x 42nm x 175nm  Output is water – approx. glucose absorbed  Fuel tank – glucose storage – 42nm x 42nm x 115nm  Mechanical or hydraulic power distribution Rods & gears Pipes & valves  Control – onboard computer

Baseline Design - Communications  Physician – broadcast signals  Modulated compressive pressure pulses  Mechanical transducers – surface of respirocytes  Transducers – pressure driven actuators  Internal Communication Hydraulic - Low pressure acoustic spikes Mechanical - Mechanical rods and couplings

Baseline Design - Sensors SSorting rotors – quantitative molecular concentration sensors IInternal pressure sensors – gas tank loading, ballast and glucose fuel tanks, internal/external temperature sensors.

Baseline Design – Onboard Computation  10 4 bit/sec computer  10 5 bits of internal memory  Gas loading and unloading  Rotor field and ballast tank management  Glucose engine throttling  Power distribution  Interpretation of sensor data  Self-diagnoses and control of protocols

Glucose rotor, Tank, Engine and Flue Assembly in 12-station Respirocyte baseline design

Pumping Station Layout

Equatorial Cutaway View of Respirocyte

Polar Cutaway View of Respirocyte

Baseline Design – Tank Chamber Design  Diamondoid honeycomb or geodesic grid skeletal framework  Perforated compartment walls  Present design – CO 2 and O 2 separate  Proposed – same chamber  Disadvs Respiration control – CO 2 level Reverse CO 2 overloading Reduction of maximum outgassing rate

Therapeutics  Minimum Therapeutic dose Human blood O 2 capacity – 8.1 x molecules Each respirocyte – 1.51 x 10 9 O 2 molecules Full duplication – 5.36 x devices Hypodermal injection or transfusion  Maximum Augmentation Dose Fully O 2 charged dose – 9.54 x respirocytes 12 minutes and peak exertion 3.8 hours at rest  Control Protocols Precise external control by physician Programmable for sophisticated behaviors

Safety and Bio-compatibility  Mechanical failure modes Device overheating Non-combustive device explosion Radiation damage  Coagulation  Inflammation  Phagocytes

Applications  Transfusions  Treatment of Anemia  Fetal and Child-related disorders  Respiratory Diseases  Cardiovascular and Neurovascular applications  Tumor therapy and Diagnostics  Asphyxia  Underwater breathing  Endurance oriented sport events  Anaerobic and aerobic infections  Veterinary medicine

Summary and Conclusion  Artificial erythrocyte  Avoiding carbonic acidity – mechanical transport of CO 2  236 times more O 2 per unit volume than natural RBCs  Tough diamondoid material  Numerous sensors  On-board nano-computer  Remotely programmable  Lifespan of 4 months  Future advances in molecular machine system engineering – actual construction.

References  Drexler KE. Nanosystems: Molecular Machinery, Manufacturing, and Computation. New York: John Wiley & Sons, 1992.Nanosystems: Molecular Machinery, Manufacturing, and Computation 

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