Towards Active Matter which is

Autonomous, Self-propelled and Living

J.V. YakhmiHomi Bhabha National Institute, MumbaiAtomic Energy Education Society, Mumbai

(Email: ya_kmi@yahoo.com)(Former Associate Director, Physics Group,

Bhabha Atomic Research Centre)

Talk at VECC, Kolkata, Sept. 11, 2014

What is life?● No exact answer● However, one agrees that living things

have abilities to:– self-organize;– metabolise;– respond to stimulation;– self-regulate;– grow and differentiate;– inherit and reproduce;– evolve.

… he moves, he is alive! …..Life is MOVEMENT

Physics Materials Science& Engineering

Chemistry

Soft Matter & Materiome Lie at multidisciplinary interface

Venkatarman Ramakrishnan a Ph.D. in Physics, worked in a Molecular Biology Lab to get 2009 Chemistry Nobel for …. ….’the protein producing ribosomes, which transform DNA into LIVING MATTER – like sk in and immune system… ’.

Biology

BIONIC Connections COMBINING MOTOR AND SENSORY INPUT

While imparting movement, we humans (vis-à-vis NATURE) have an obsession with WHEELS, Pulleys, Gears etc.,

Prosthetic Design using the INTERFACE between lab-grown nerve fibers and conducting polymers.

Linking artificial limbs to the nervous systemScientific American, Jan. 2013, p. 52

Materiomics for Active Living Matter● Synthetic Materials have limitations vis-à-vis

Biological Materials in producing autonomousmovement, self-propelled locomotion, & LIFE

● Bio-inspired Soft Matter, MATERIOMICS, self-assembly, hierarchical structures

● Self-organization, motor proteins, chemotaxis,magneto-taxis, Cell, Bacteria, Flagella, cilia

● chemo-mechano-chemical conversion of energy

● Self-regulation and Synthetic ACTIVE Matter

For the FIRST time an entire Living Organ grown from lab-created cells: Bredenkamp et al, Nature Cell Biology, published online 24 Aug. 2014 - a thymus (an organ next to the heart that produces immune cells, called T cells, which guard against disease), created from cells that were created outside of the body by reprogramming

Induced thymic epithelial cells (iTEC) transplanted onto the mouse k idney form an organised and functional mini-thymus (kidney cells in pink, thymus cells in dark blue)University of Edinburgh

artificial cilia grown…. Tellcamp et al (Kiel University) Eur. J. Org. Chem. 2014, 5456

MNP-loaded Polyurethane film for Artificial Heart BARC & Ramachandra Med. college, Porur, Chennai

Inventors: S. M. Yusuf, K. R. Balakrishnan* and J. V. YakhmiUS Patent US/2012/ 0323318A1 filed on: 03-03-2010. Published on Dec 12, 2012 International Publication No. WO2011/107996A1, dated 09-09-2011 *Now Director, Cardiac Sciences, Malar Fortis Hospital, Chennai

HemisphericalMagnetic MembraneDiameter : 8 cmThickness : ~ 0.3 mm

Design of Synthetic Materials with HOMEOSTASIS?Living organisms survive due to homeostatic abilities (control of their body T, BP, pH and sugar levels), achieved via inter-conversions of chemical and mechanical energy, and self-regulating feedback loops.

e.g. chemical energy into motion and vice versa, such as synthesis of ATP (energy currency coenzyme adenosine triphosphate) & muscle contraction.

With limited uni-directional chemo-mechanical or mechano-chemical modes, synthetic materials cannot perform self-monitoring/self-regulating behaviour.

Can we create self-regulating, homeostatic materials which provide precise chemo-mechano-chemical feedback loops at nano/microscale? Perhaps ..

using bilayers with hydrogel-supported, catalyst-bearing microstructures.Synthetic homeostatic materials with chemo-mechano-chemical self-regulation, Nature, Vol. 487, (2012) p. 214

Chemistry

Physics

Biology

1 GeV ~ 1.3 * 1013 K

Thought

Life

Towards Complex Matter

from particles to atoms, to molecules, to life, and on to the thinking organism

LIFE on Earth: can grow, can reproduce, can evolve!!

• All living things are composed of organic material (C, H, O, N, P, S).

• life comprises strings of DNA & RNA whichform amino acids, which in turn form proteins

Origin of First Life (single celled) on Earth ~3.5b yrs agoOrigin of Universe: ~13 bn yrs ago

Miller-Urey experiment (1953): life from C, H, O, N, P, S?– Primordial soup (Water, Methane, CO2 & Ammonia)– Energize it with a spark (UV for later)– Found amino acids after a few days - Not living

organisms, but the building blocks of proteins!

Conducting Miller-Urey ExperimentsEric T. Parker (Georgia Inst. of Tech) et al , Journal of Visualized Experiments (Video Journal, Publ. Jan. 21, 2014)

BronzeCu

Iron

Steel

Metallurgy

High Q steel

Al

Hi-strengthAl-alloys

Super alloys

Alloys forbody parts

Sp. Alloys for Turbines

We have seen evolution of materials/ structures , composites. There is a need to develop smart, intelligent structures

Shape Memory Alloys….it is movement!

Spider silk: 5x strong vs steel, Reusable by spider.CNTs: 6 times lighter vs. steel, 100x more rigid. Graphene: 1 atom thick - soft!Slimmest & richest!

Nature’s Flexible Dermal Armor Adv. Mater. (2013) 25 pp. 31-48, W. Yang et al

(a) The scales overlapping on the pangolin body,

(b) A lioness tries to defeata pangolin dermal armor. She finally gave up.

Materials Design in 21st Century is moving more and more towards Marvels of Nature… their toughness, strength, flexibility and the way they produce controlled movement

Unmanned DRONES. NUAV (Nano Unmanned Aerial Vehicles) for reconnaissance in airPhysics of Flying..Look to NATURE!Material Design by Nature…. …..for Movement…. for LIFE

Flying Artificial Insect

Man-made flying machines no match for Nature Because Nature’s flying machines have evolved,

& are more advanced than Modern airplanes—they can even repair and reproduce themselves.

Laws of Physics still apply to all birds in flight!!

A BOTBEE

BIRDS: Nature uses 1. Right materials: Very light hollow bones. Strong skeleton2. Optimal Design Features: Heavy organs, muscles

placed at center of the body, for balance.Feathers: lightweight, flexible, strong for the size/weight.Aerodynamic marvel. Barbs, barbules for wind-resistance. Hooks on barbs. Overlapping feathers – with smooth, angular, air-resistant surfaces. Feathers also provide “bays” for the feet during flight

Birds in flight – Glide, soar and swoop!Many birds have multiple locomotion capabilities Fly, walk, swim, dive, dig

But for cross-members (hollow bones, a concept now used in aircrafft wings), vultures would break to pieces in mid-air, when they dive to catch a victim with speeds of 250 kms, using wings as brakes.

Can we design multi-task ing autonomous robots w ith flex ible actuators? I t is a materials problem!

Controlled Flight of a Biologically Inspired, Insect-Scale RobotScience, 340 (2013) 603

80-mg, insect-scale, flapping-wing robot Fly- with a high-power-density piezoelectric flight muscles, and - 2 independently actuated wings enable precise control

of torques about three orthogonal axes.

Just nearest-neighbourperception

Self-organizationcollective movementof birds. No Leader!

The flow of ants is dependent on their ability to detect others and the rate at which they turn during avoidance maneuvers!Locusts! Honeybees!

collective movement of mammals. No pre-existing tracks.

what a co-operation!

Molecular Self-assembly: fabrication of many useful materials (wood, bioceramics, bone, spider silk, magnetite crystals, etc.) by NATURE from building blocks

spider silk

Plants, too, have Hierarchical structure 4 building blocks (cellulose, lignin, hemicellulose and pectin) By varying their arrangement in the cell wall, and the cellular structure, a large range of mechanical properties (Strength, Young’s modulus ) is produced in plants

J. R. Soc. Interface 9 (2012), 2749

Self-assembly: Mastered by Nature! Mostly SOFT MATTER

E. Coli bacterium Unicellular organismsince >1 billion years : it hasSensors, memory, actuators (flagella,i.e. nanoscale molecular motors)

HDL (”good cholesterol”): High-Density Lipoprotein, 8–11 nm sized biomolecule aggregates having cholesterol, phospholipids, proteins etc.

LDL (”bad cholesterol”) Low-Density Lipoprotein, 18–25 nm sized similar aggregates

LDL HDL

Polysaccharides

Biomembranes

Nature (self)assembles biopolymers from families of building blocks Carbohydrates from Sugars; Membranes from lipids (Glycerols / FAs); Nucleic Acids from Nuleotides; Proteins from Amino Acids (hierarchy),

Sugars

Lipids

Nucleotides

Peptides Proteins

RNA / DNA

Self-assembly by Nature (bottom-up approach) :energy economy – non-covalent interactions;

– ambient regimeStructural materials (wood, bioceramics, bone, spider silk , magnetite)DNA, Proteins, Viruses, Bacteria… : coded self-assembly

Ambitious yet to compete in the lab!(self-organization, self-repair, self-replication)Nature’s assembly-line doesn’t make a mistake!

Simple Self-assembly∗ Float glass; ∗ Growth of single crystal from seed.

Self-assembly in the lab (BARC)Bulk: Self-assemble functionalized molecules into a lattice

Films: ∗ Self-assembled monolayers (SAMs);∗ Amphiphilicity at air-water interface (LB films);∗ Electrochemically grown films

SEM of dendrites of DNA-NiHCF conjugates at 75º C (scale bar – 100 µm).

Dendritic fractals appear at 75º CEach lobe is about 10 micrometer in size. NiHCF particles within these aggregates retain their physical shape and size.

Surface of dendrimer curls with numerous chain-ends, acting as a template directing the self-assembly of nanocrystal aggregates of NiHCF along the tip of a branching unit.

a single dendrite of DNA-NiHCF conjugate. Scale bar- 20 µm cubic crystals w ithin

dendrites (scale bar – 5 µm)

DNA as a template to prepare nanocrystalsBagkar, Choudhury, Bhattacharya and Yakhmi,J. Phys. Chem. B 2008, 112, 6467–6472

The basic unit of life is the cell: (Hooke)In 1665, Robert Hooke, made an improved microscope and viewed thin slices of cork. Saw plant cell Walls. Hooke called them ‘CELLS’

R. Hooke (1635-1703)

We contain about 1014 cells, enclosed by a fluid-like thin plasma membrane.

Membrane encloses subcellular organelles – nucleus, mitochondrion, Golgi complex…

ANIMAL CELL

Cells with a nucleus: "EUKARYOTIC“, e.g. animal cellsCells without nucleus: “PROKARYOTIC”

● A cell manufactures its internal structure, to grow● Most cells can reproduce by mitosis● Cells maintain a resting electrical potential difference

between their interiors and the outside world● Cells can sense internal/environmental conditions, and

then do proper feedback. Apoptosis is an extreme form of feedback, making a cell destroy itself.

A cell takes in chemical/solar energy, most of which gets discarded as heat, but a fraction turns into mechanical activity or is used for synthesis of energy-storing molecules

●Many cells can move, by crawling/swimming, etc.….. And talking of MOVEMENT…

Joints

Exoskeletalpiece

NATURE DOES NOT USE WHEELS!An ant can support weights hundreds of times its own! its strength and mobility is due to an exoskeleton made of chitin, and three pairs of jointed legs.

Can one make artificial muscles, artificial sk in, tissue… ??!!

(a) Vapp = 0V (b) Vapp = +2V (c) Vapp = -2V

Microactuators (ARTMUS) from Polypyrrole (Ppy) doped with DBS (dodecylbenzene sulfonate, C12H25C6H4SO3

-) anionsPPy+(DBS-) + e- + Na+(aq) ↔ Ppy0(DBS-Na+)

NN

NN

NN

HH

HH

H

H

( )

Na O3S

Na+ diffuses in and out of PPy during electrochemical switching. A reduction in volume occurs when the ions exit (during oxidation) and vice versa

Sutar, Aswal, Gupta and Yakhmi Jl. of Pure and Appl. Phys 45 (2007) 354

Cells contain biological motors that convert chemical energy into rotary / linear motion. These bio-motors are the forerunners of synthetic molecular motors.

ATP synthase is a rotary motor protein that is responsible for the synthesis of adenosine triphosphate (ATP), the universal fuel of a cell.

Proteins like myosin, kinesin and dynein, are linear motors that travel along polarized cytoskeletal filaments powered by the hydrolysis of ATP.

Myosins move along actin filaments and are involved in activities such as muscle contraction;

Kinesin and Dynein walk along microtubules, transporting cargoes within the cells.

Animation of myosin at work

Myosin is a motor protein that is used in muscle.

Processive motion speeds in natural myosins have previously been recorded upto 7μm s–1.

The new motor uses bidirectional myosin - can proceed in both forward and backward directions.

Natural Myosins have two motor domains (or heads)

Schindler et al, Nature Nanotechnology, 9 (2014) 33 have have fabricated 3-headed and 4-headed myosins.

Further, by introducing flexible elements between heads, they could optimize the stepping which allowed these modified cytoskeletal motors to travel along the filament tracks at up to 10μm s–1

Important motor proteins: myosin, kinesin and dynein

KINESIN walking along a microtubule carrying a cargo.

Kinesins are microtubule-associated motor proteins that convert chemical energy released from nucleoside triphosphates (ATP) into mechanical energy.

Dynein and its arrangement in sea urchin sperm flagellasea urchin sperm cell

flagellum viewed in cross-section

Cross-section of DMT (outer doublet microtubule)

MTBD = Microtubule binding domain

Dyneins are large microtubule motor proteins required for mitosis, intracellular transport and ciliary and flagellar motility. But how do they move? MECHANISM?Rotation of the head relative to the linker is the key action in dynein movement- Lin et al, Nature Cell Biology 16 (2014) 479 using cryo-electron tomography

They generate force through a power-stroke mechanism, which is an ATP-consuming cycle of pre- and post-power-stroke conformational changes that cause relative motion between different dynein domains.

Interface: Materials science (“synthetic”) with Biology (“life”)

Convergence of disparate fields–MATERIOMICS Adv. Mater. 25 (2013) 802

Colloids + polymers + surfactants = Soft Matter (rubbers, gels, creams, paints, soaps, liquid crystals, proteins, cells, enzymes, Bio-macromolecules …)

“Materials that are held together by weak non-covalent interactions Electrostatic charge–charge, dipole-dipole, H-bonding, Hydrophobicity), which are ~ kT, and thus comparable to entropic forces”

The phrase was coined by Pierre-Gilles de Gennes (1932-2007) in his 1991 Nobel Prize acceptance speech (COMPLEX FORMS OF MATTER in Citation). Soft Condensed Matter can flow like liquids (have viscosity), it can bear stress (elastic deformation) like solids. It is Viscoelastic (viscous + elastic)

Colloids (milk, blood, clay, paints….) are dispersed phases (1-200nm) in a continuous phase.

Colloids lie between suspensions and solutions

Colloids

Thermally driven motion of colloids -Brownian Motion

A red blood cell (deflated shape) flickers when observed under phase contrast.

the insoluble bilayer optimises its area at fixed surfactant number.

Shape fluctuations of “vesicles”, (the flicker) is an example of Brownian motion for a flexible object.

- a good example of soft matter

If it takes ~ 500 genes to self-sustain a chain of polymeric (nucleic acids, proteins) reactions !!then the smallest life form utilising nucleic must be colloidal.

Colloidal size confers some motility even without specialised propulsive mechanisms (flagella). Colloidal Particles can remain suspended and diffuse significant distances by Brownian motion.

DNA, Cell membrane, proteins…. Soft matter is ubiquitous! We are soft matter!Virus, E-coli, pathogens… Our problems are also Soft Matter!

Emulsifier in action

polymers Dendrimer

Liquid Crystals

Soft Matter: Polymers e.g. rubbers; plastics (polystyrene, polyethylene); biomolecules (proteins, DNA, starch…..), etc.

Amphiphilic Molecules (e.g. a phospholipid)Hydrophilic (Polar) Head, has a charge and is

attracted to water.Hydrophobic Tail: long hydrocarbon chains made up

of C and H, are NON- POLAR, repel water.

air-water interface used to grow functional materials/crystals

soap bubbles: are bilayers of detergent molecules

Being hydrophobic, lipids form stable bilayers (viz. Cell Membrane)

K+ ions on DODA-NiHCF nanoparticles deposited as LB films

CVs of 19 layer film of DODA-NiHCF shows response todifferent K+-ion concentrations using 0.001, 0.01, 0.1 and 1.5M KCl solutions.

-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

-8.0x10-6

-6.0x10-6

-4.0x10-6

-2.0x10-6

0.0

2.0x10-6

4.0x10-6

6.0x10-6

8.0x10-6

1.0x10-5

1.5M0.1M

0.01M

0.001M

I (A)

E (V)

Peak potential shifts with increase in K+ concentration.

During reduction, the film takes cations from the solution. During oxidation (on the hcf centers) the cations are released from the film.

During oxidation/reduction reactions e’s are exchanged between the electrode and particle, whereas K+- ions are exchanged between the particles and adjacent electrolyte.

K+ ions neutralize negative charge and make the film maintain charge balance.

Bagkar, Betty, Hassan, Kahali, Bellare and Yakhmi, Thin Solid Films, 497 (2006) 259

adhesion of blood platelets to the arterial surface Cell surface modified with phosphatidylcholine adsorbs albumin preferentially, helping in reducing cell adhesion.

Goal: deposition of LB films ofphospholipid L-α- Phosphatidylcholine (PTC), i.e. egg yolk, glycolipid Galactocerebroside (gal) and cholesterol (Chol) in the ratio (1: 0.7: 0.125, the cell mimetic composition) on polycarbonate (PC) membrane surfaces;

AND study their blood compatibility and adhesion on the surface.

Sree Chithra Tirunal Inst. for Med. Sci. and Technology, Trivandrum and BARC

Self-assembly also at liquid-liquid interfaceSynthesis of long 1000 µm, ~25µm dia polyindole fibers Koiry, Saxena, Sutar, Bhattacharya, Aswal, Gupta, Yakhmi, J Appl. Polymer Sci. 103 (2007) 595

Lungs aren't hollow bags, but spongy tissue w ith many infoldings! Gas exchanged between air and blood in respiratory bronchioles and numerous tiny alveolar sacs(1.5 billion alveoli/lung provide huge surface area for gas exchange).

Bio-medical Engineering: simulation of Lung Surfactant films using Langmuir-Blodgett technique (prevent RDS)

55000 diabetes related (gangrene) amputations in USA/year!Loss of limbs at farms/in accidents/burns/frostbite… Jaipur foot!

Imagine if severed limbs could Regenerate (self-repair)!

Some vertebrates (Amphibians) can regenerate their limbs!

Salamanders can do so in 40 days! Amphibian, human limb structure analogous

Human limb: bones, muscles, cells, sk in

Human wounds are sewn up! Then no signals go to underlying cells to regenerate. Finger regeneration was discovered in a human when wound was not sewn up!

Human bone replacing itself, gradually even in adults at a rate of a few % per yearcells of two kinds: Osteoclasts: resorb bone by releasing (acid + enzyme); Osteoblasts: make new bone.

osteoclasts and osteoblasts, work in sequence, to eat away old and generate new bone.

Bone – light but strong bioceramic. A marvel!small cracks self-detected, self-repaired.

Can we devise nanostructured formulations?

Moving FrontSLOW….

Hierarchical structure of bone showing 7 levels of hierarchy.

The mineralized collagen fibrils are the basic building blocks of bone.

They are composed of collagen protein molecules (tropocollagen) formed from three chains of amino acids.

Annu. Rev. Mater. Res. 40 (2010) 25

amino acids~1 nm

Fiber patterns~50 mm

Osteons andHaversian Canals~100 mm

Bone tissue~50 cm

Tropocollagen~300 nm

MineralizedCollagen fibrils~1 mm

Fibril arrays~1o mm

Mechanics-Materials ConnectionsMATERIALS SCIENCE influences BIOLOGY: mechanical properties of the extracellular matrix (ECM) influence the living organisms

Building blocks of Bio-materials are combinations of:minerals (which are weak in tension) and biopolymers (which are weak in compression) .

Combine “protein-toughness” + the “mineral-stiffness”.TOUGHNESS comes from Control of interfacial features-

viz. friction, H-bonds, chain straightening/stretching.

BIOLOGICAL materials differ from SYNTHETIC because of: (i) Self-assembly (bottom up approach); (ii) Hierarchy; (iii) Hydration; (iv) Mild synthesis conditions; (v) Evolution, (vi) Self-healing capability, and(vii) Multi-functionality: viz. bird-feathers for flight capability,

camouflage, and insulation. Bird-bones provide tructuralframework, and protection to internal organs

Biological materials: antler, dentin, bone and enamel made by NATURE by ‘‘reinforcing” (by combining)

the protein-toughness and

the mineral-stiffness.

Toughness vs. Stiffness

Engineered synthetic materials: metals, alloys and ceramics

materials design paradigm -- UNIVERSALITY

+ STRUCTURAL DIVERSITY

building blocks of collagen-based bio-materials –

(i) Bone, (ii) Cornea and (iii) tendon

are universal

But there is much structural diversity beyond the fibril scale

Universality and diversity of protein materials

DNA nucleotides (ACGT – Adenine, Cytosine, Guanine and Thymine) are UNIVERSAL. Arranged in different patterns, they produce DIVERSE genetic sequences , functions and all proteins.Protein structures (like topoisomerase protein, shown here whose role is to cut strands of DNA double Helix ) too have UNIVERSAL motifs: AH (alpha-helices) , BS (beta-sheets) and RC (random coils), arrangements of which produce DIVERSE proteins (e.g. enzymes, fibres, filaments). HFSP J. 4 (2010) 26–40

Nature imparted different stiffness (Mechanical properties) to amyloid (protein aggregate) fibrils and other biological materials

Pathological Amyloids (protein aggregates), their location and role in diseasesAlzheimer’s disease Amyloid-β (aβ) peptide Extracellular CNSParkinson’s disease α-synuclein Intracellular CNSAlzheimer’s disease Tau protein Intracellular (CNS)Prion diseases Prion protein Extracellular (CNS)Huntington’s disease Polyglutamine-rich proteins Intracellular (CNS)Type II diabetes Amylin Extracell. (pancreas)

Extracellular materials (collagen, bone, enamel and silk) are stiffest, ‘intra’, much less.

Brittle Materials (ceramics, Si, glass) fracture through crack propagation, mediated by continuous breaking of atomic bonds.

Deformation of materials under extreme mechanical loading

Ductile Materials (Cu, Ni) deform through dislocation nucleation, and creation of dislocation networks

Biological materials are hierarchical - heterogeneous assembly of building blocks (like protein molecules, nanocrystals) whose mechanical and interface properties are not well-established.

i) Crack initiation occurs during a damage event.

ii) Crack propagation ruptures a microcapsule and releases epoxy monomer healing agent, which migrates along the crack by capillary action.

iii) Healing agent undergoes ring-opening polymerisation on contact with the , Sc(III)triflatecatalyst particles, and the exposed crack planes get bridged with this new polmer.

A self-healing Polymer system. Adv. Funct. Mater. 21 (2011) 4624

Uses a pre-embedded dispersion of epoxy solvent loaded microcapsules and catalyst particles. Recovery of over 80% fracture strength is achieved

the crack must travel around the tiles in Abalone, instead of through them: Abalone nacre showing growth (meso)layers, mineral bridges between mineral tiles and asperities on the surface, the fibrous chitin network that forms the backbone of the inorganic layer.

SCIENCE VOL 339 (15 Feb. 2013) p. 773

Nature resists crack formationin the first place! - TORTUOSITY

Caenorhabditis elegans, a 1 mm long roundworm, is a model organism. It is small (<1000 cells), transparent, and genetically tractable.

Simple, but exhibits complex phenotypes associated with multicellularity: it has differentiated cells and organs, it ages and has a lifespan, and it is capable of learning and remembering.

Simplicity and complexity makes it a useful model in determining the relationship between:

molecular-scale phenomena and organism level phenomena, such as, aging behavior, cognition, and disease.

The WORM: Integrating Chemical and Biological ResearchHulme and Whitesides Angew. Chem. Int. Ed. 2011, 50, 4774 – 4807

CHEMOTAXIS: Cells sense chemical gradients, communicate this information throughout the cell, and change their shape in response

Chemotaxis can help sperm find the egg cell during fertilization.

Chemotaxis also aids the spread of cancer during metastasis (cells leaving the primary tumor to seed new tumors in other parts).

A small scratch on the skin – the pain goes away quickly. Due to quick healing by neutrophils (type of white blood cells) that remove bacteria from a wound. Neutrophils reside in the circulatory system, but when required, can leave the bloodstream, and navigate through connective tissue to the injured area.

Phys. Today (2013) 25.

Magnetotactic Bacteria, MTB, found (105–106/ml) at the sediment-water interface

Magnetite particles in Aquaspirillum

Magnetotacticum [TEM image]

Hunting for magnetotactic bacteria in themud of the German Wadden Sea

MTB cells contain intracellular crystals(Monodisperse 35-120 nm, Single domain) of magnetite Fe3O4, in magnetosomes, aligned in a chain.

Magnetic moment of individual crystals add up!MTB thus act as stable magnets (dipoles).They can align along magnetic field lines, like a compass needle, as they swim - Magnetotax is

Motion of flagella. A flagellum usually undulates, its snakelike motion driving a cell in the same direction as the axis of the flagellum.

Motion of cilia. Cilia have a back-and-forth motion that moves the cell in a direction perpendicular to the axis of the cilium.

Cell motility via flagella and cilia

Bacterial flagellar motor is driven by the flow of ions across the plasma membrane. Rotation of long helical filaments, protruding from the cell, propel the swimming bacteria

Bacterial Flagella: Flagellar Motor; Berry, R. M., Encyclopedia ofLife Sciences; John Wiley & Sons, Ltd.: Chichester, 2001; pp 1−8

Biomotors:(analogous to Earth’s rotation & revolutions)

1. linear motor2. rotation motor.

and recently a third type 3. a motor that revolves without rotation

These motors use ATPase

Viral DNA-packaging motor: a rotation motor with double-stranded (ds) DNA serving as a bolt and the protein channel as a nut.

Rotation motors use parallel threads to operate with a right handed 2nm channel, while revolution motors use a left-handed >3nm channel to drive the right-handed DNA in an anti-chiral arrangement.Biotechnology Advances

32 (2014) 853–872

phi29 bacteriophageDuda and Conway, Structure 16 (2008) 231

Spooling of DNA within capsids of phagesoccurs to support the revolution mechanism

Formation of the toroidmight be results of the DNA revolution motion during the packaging

Active Materials under development !

Natural and synthetic active colloidsAn active colloid: a suspension of particles that transduce free energy from the environment to produce various non-equilibrium activities , e.g. growth, replication and self-propelled Motility.

Some self-propelled ACTIVE COLLOIDS exist in Nature: viz. suspension of motile bacteria (viz. Escherichia coli).

Synthetic self-propelled colloids (colloidal `swimmers') prepared recently (two-faced, or Janus, particles .whose synthesis was first proposedP.-G. de Gennes in his Nobel lecture). These are propelled by chemical reactions on their surfaces. Janus polystyrene spheres half coated with platinum are motile in an aqueous solution of H2O2.

ACTIVE bacteria (colloids) can sense their environment and produce active behaviour - `taxis'.

W. C. K. Poon, Proc. of the Int. School of Physics Course on “Physics of Complex Colloid", Bologna (2013), pp. 317-386

Self-organization in a suspension of synthetic photoactivatedcolloidal particles arises from nonequilibrium driving forces.

2-D “living crystals,” form, break, explode, and re-form elsewhere.Science 339 (2013) 936

(A) SEM of the bimaterial colloid: a TPM (3-methacryloxypropyl trimethoxysilane) polymer colloidal sphere with protruding hematite cube (dark).

(B) Living crystals assembled from a homogeneous distribution (inset) under blue light.

(C) Living crystals melt by thermal diffusion when light is extinguished: Image shows system 10 s after blue light is turned off (inset, after 100 s).

Swarming and swirling in self-propelled granular rods, to bacterial colonies

A. K., G. Lumay, D. Volfson and L. Tsimring, PRL (2008)

Can there be Spontaneous motion in hierarchically assembled ACTIVE MATTER?

Drops of ACTIVE materials (built from from microtubule bundles), have been shown to get LIBERATED FROM EQUILIBRIUM CONSTRAINTS, and attain tunable emergent properties of far-from-equilibrium materials.

There is a need to develop statistical mechanics of active matter!.

Water-in-oil emulsion droplets exhibit spontaneous autonomous motility when partially compressed between chamber surfaces. A droplet trajectory taken over a time interval of 33 min is overlaid onto a bright-field droplet image. Nature Vol. 491 (2012) p. 431

self-organized rotating bacterial spiral coils: Brownian dynamicsSoft Matter, 2014, 10, 760

the cells – bacterial swarms, are motile within the thin liquid layer between the agar gel and the air

Folding process of Spiral Coils

Scale bar: 10µm

A self-propelled synthetic (bio-hybrid) swimmer at low Reynolds number, Williams, Anand, Rajagopalan, and Saif, Nature Commun. (Published 17 Jan 2014)

A polydimethylsiloxane (PDMS) filament with a short, rigid head and a long, slender tail, on which cardiomyocytes, when cultured, contract and deform the filament to propel the swimmer at 5-10 µms-1. (2-tailed swimmer upto 81µms-1)

Can use optogenetic muscle cells for light-actuated sw imming, neurons and muscle cells for sensor-based sw imming, turtle cardiomyocytes and fibroblasts for room temperature sw imming

Applications: transport and delivery of cargo, and as model for more complex biological machines. Capability to respond to external stimulation (gradients in pH, temperature and light), and to navigate autonomously in complex fluids.

(a) Spermatozoa swim at low Re number by generating complex time-irreversible waveforms through a long, slender tail.

(a) Biohybrid swimmer. An elastic filament with a rigid head and a compliant tail,and a cluster of contractile cells generating a force F at a distance w/2.

(c) SEM of a PDMS filament. Head and tailare 57 and 7µ m wide, and 22µm deep.

In ESSENCE Non-equilibrium processes convert chemical energy into mechanical motion to enable the motility of organisms (such as bacteria), via cilia and flagella.

Autonomous motility & spontaneous cilia-like beating due to hydrodynamic instabilities has been reproduced in vitro, by using a biomimetic active motormicrotubule assemblage.

Cilia-like motion of synthetic active filaments has also been observed.

The first directed motion in evolutionary biology, emerged in cilia, more than a billion years ago.

Cilia-driven directed motion comes from Chiral, unidirectional molecular switches mounted on surfaces.

Paramecia with artificial cilia. Tellcamp et al (Kiel University) Eur. J. Org. Chem. 2014, 5456Simple azobenzenes are transformed into chiral switches equipped with a molecular platform to mount them on Au-surfaces.

Self-regulated intelligent systems (SIS) using chemical oscillators, Soft Matter, 9 (2013) 4956

SIS exhibit autonomous, reversible and periodical variations without any external stimuli (e.g. heartbeat, brain waves, pulsatile secretion of hormones, cell cycles and biorhythms). The self-regulated state is sustained over a long period of time outside the thermodynamic equilibrium.

Self-oscillating Smart polymers and gels have been developed utilizing chemical oscillators based on the Belousov–Zhabotinsky (BZ) reaction, and polymers or gels prepared via copolymerization of N-isopropylacrylamide (NIPAAm) and double bond modified Ru(bpy)3 (catalyst of BZ reaction).

Continuous energy transduction procedure drives the systems to exhibit autonomous, reversible, and periodical behavior. For instance, for the self-oscillating polymer, the energy for mechanical motion (soluble/insoluble, selfbeating and self-walking) is derived from the energy released from the oxidation of organic acid in chemical oscillators.

self-regulated supramolecular assembly (SSA) systemChem. Commun., 48 (2012) 10553

In Belousov–Zhabotinsky (BZ) reaction, Ru-ion acts as a catalyst, changing periodically between Ru(II) and Ru(III) states, is a good choice.

Prefabricated branch-like assembly is dissolved into a BZ reaction solution containing certain concentrations of NaBrO3, malonic acid and H2SO4.An autonomous transformation occurs between the assembled and the de-assembled state, accompanied by the periodical colour change.

Self-regulated intelligent systems (SIS) using chemical oscillators, Soft Matter, 9 (2013) 4956

ORGANIZED SELF-OSCILLATING MICROGELS: for soft actuators in microfluidic devices/ self-beating micropumps Soft Matter 8(2012)11447

swelling–deswelling or cooperative dispersing–flocculating motion of POLYMERIC microgels. Amide groups provide cross-linkers

Ru(bpy)3 acts as a catalyst for the Belousov–Zhabotinskychemical oscillating reaction, which generates rhythmical redox changes between Ru(III) state to Ru(II) state.

hierarchical structure can get large amplitude of swelling–deswellingoscillation in the artificial muscle.

self-oscillating polymer gels as autonomous systemsYoshida and UekiNPG Asia Materials (2014) 6, e107; doi:10.1038/am.2014.32

‘self-oscillating’ gels that undergo spontaneous cyclic swelling–deswelling changes without any on–off switching of external stimuli, as with heart muscle. The self-oscillating gels were designed by utilizing the Belousov–Zhabotinsky (BZ) reaction, an oscillating reaction, as a chemical model of the tricarboxylic acid cycle.

Autonomous amphiphilic assembly driven by a pH-oscillator exhibitingvesicle/micelle transition.Langmuir 26 (2010) 13770

A pH oscillator controls rhythmic inter-conversion of nano-scale vesicles and micelles made of fatty acids.

Changes in pH combined with diffusion, trigger self-assembly of patterns of vesicle/micelle “stripes” or concentric “shells”.

Organic Photomechanical Materials

Kim et alChemPhysChem15 (2014) 400 – 414

Organic molecules can transform photons into Angstrom-scalemotions by undergoing photochemical reactions.

Ordered media, like liquid crystals or molecular crystals, can align these molecular-scale motions to produce motion on much larger (micron to millimeter) length scales.

Photocontrolled alignment in liquid crystals,Nicoletta et al, Membranes 2012, 2, 134

Uses biodegradable hydrophobic polycaprolactone (PCL) and thermoresponsive hydrogel, PNIPAM, poly-(N-isopropylacrylamide).

Stoychev et al, Soft Matter 7 (2011) 3277-3279

Folding star-shaped polymer bilayer for cell-culturing. Swelling of the thermoresponsive hydrogel layer at lower temperature increases stress in the film that results in bending of the star arms and folding.

E. coli swim by rotating helical filaments driven by motors embedded in the cell wall. The motors switch between clockwise (CW) and counter-clockwise (CCW) directions of rotation to bias cell movements in response to chemical gradients.But how do Bacterial Flagellar Motors sense Mechanical Stimuli? Lele et al, PNAS 110 (2013) pp. 11839–11844

(A) A cell is brought up to a 1-μm latex bead held in an optical trap. The bead binds to a short sticky-filament stub and its rotation is monitored.

(B) A cell with a short sticky-filament stub is allowed to settle onto the surface of a glass cover-slip and selftether.The rotation of the cell body is monitored.

Bright-field microscopy of homogeneous silica rods under applied field of 50 Vmm-1 at (a) 100 kHz and (b) 30 MHz. The scale bar =10 µm.Soft Matter 10 (2014) 1320

electric field-induced assembly of Janus colloids composed of silica rods patterned with Au-patches in both side- and tip-coated motifs

synthetic DNA walker that transports NPs along 1D (non- DNA) SWCNT tracks, coated with with RNA molecules, which the motor —a DNA enzyme - uses to fuel its steps along the track. Choi et al Natrue Nanotechnology 9(2014) pp. 39-43

Behaviour similar to motor proteins: The processive and autonomous motion along the track is similar to

motor proteins in cells;DNA motor can carry inorganic cargo (CdS NPs), like motor proteins the motors can walk several micrometres

Behaviour different from motor proteins: whereas kinesin and dynein proteins can take forward and backward steps along their tracks, the DNA motor destroys its track when it walks and can, therefore, only step in one direction. travel at speeds of up to around 0.1 nm s–1. Like other DNA motors, these motors are much slower than motor proteins.

However, one can start and stop the motion of these DNA motors remotely by altering their chemical environment.

Thanks for your attention!!.....