self assembly technique in rigenerative medicine

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Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of Italy

Mail:[email protected]@cnr.itAddress:Viale Kennedy, 54 - Mostra d'Oltremare Pad. 20 - 80125 Napoli NA CampaniaFax.:(0039) 081 2425932

Self assembly technique in rigenerative medicine


INTRODUCTION

DEFINITION

Self-assembly is a process in which components, either separate or linked, spontaneously form ordered aggregates

George M. Whitesides and Mila Boncheva


3


oror

Living things, planet, cosmos, etc..orbrick

Function

supramolecularpolymerStrong bondsweak bonds

or

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of Italywhy study the self assembly in tissue regeneration ?Living organisms, in particular the developing embryo, are quintessential self-organizing systems.

Histogenesis and organogenesis are examples of self-assembly processes, in which, through cellcell and cellextracellular matrix (ECM) interactions, the developing organism and its parts gradually acquire their final shape.


The success of engineering and fabricating functional living structures will depend on understanding the principles of cellular self-assembly and our ability to employ themTissue engineering by self-assembly and bio-printing of living cells Karoly Jakabet al2010Biofabrication2022001

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of Italyour ability to employ them


Analysis of the technique

The origin of today's self-assembly seems to be a natural outgrowth of a confluence of ideas taken from the work of Langmuir and Blodgettin 1935 on the formation of close-packed arrangements of amphiphilic molecules on liquid and solid surfaces and observations of Bigelowet al.in 1946 that long chain alkylamines form a densely packed monolayer on the surface of platinum. While there was no explicit mention of the term self-assembly to explain the formation of well-ordered molecular monolayers it is clear that self-assembly was operating in these systems. In 1983 Nuzzo and Allara contacted gold surfaces with alkyl disulfides and discovered they formed close-packed monolayers of chemisorbed alkanethiolate molecules, called self-assembled monolayers (SAMs)

Geoffrey A. Ozin, Kun Hou, Bettina V. Lotsch, Ludovico Cademartiri, Daniel P. Puzzo, Francesco Scotognella, Arya Ghadimi, Jordan Thomson, Nanofabrication by self-assembly, Materials Today, Volume 12, Issue 5, May 2009, Pages 12-23, ISSN 1369-7021.

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyHYSTORY

storia9

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyIrving Langmuir (1881 1957)

- ingegnere, fisico e chimico americano;- premio Nobel per la Chimica (1932);Katherine Blodgett (1898 1979)

- fisico e chimico americano;

Close-packed arrangements of amphiphilic molecules on liquid and solid surfaces A Langmuir-Blodgett film and a structure consisting of one or more layers (layer) of amphiphilic organic molecules transferred from the surface of a liquid (usually an aqueous solution) on a solid substrate, by immersion of the solid in the liquid or for emergence of solid from the liquid.

Study of ion channels that pass through the membrane phospholipid

HYSTORY.


HYSTORY.

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyTypes of Self-AssemblyTwo main kinds of self assembly

Static self-assembly (S)involves systems that are at global or local equilibrium and do not dissipate energy. For example, molecular crystals are formed by static self-assembly; so are most folded, globular proteins. In static self-assembly, formation of the ordered structure may require energy (for example in the form of stirring), but once it is formed, it is stable.

Dynamic self-assembly (D)the interactions responsible for the formation of structures or patterns between components only occur if the system is dissipating energy. The patterns formed by competition between reaction and diffusion in oscillating chemical reactions are simple examples; biological cells are much more complex ones.

Two future variants of self assembly

Templated self-assembly (T)interactions between the components and regular features in their environment determine the structures that form. Crystallization on surfaces that determine the morphology of the crystal is one example; crystallization of colloids in three-dimensional optical fields is another.

Biological self-assembly (B) is the variety and complexity of the functions that it produces.

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyTypes of Self-AssemblyGeorge M. Whitesides etc, Science, Vol 295, Issue 5564, 2418-2421 , 29 March 2002

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of Italy(A) Crystal structure of a ribosome. (B) Self-assembled peptide-amphiphile nanofibers. (C) An array of millimeter-sized polymeric plates assembled at a water/perfluorodecalin interface by capillary interactions. (D) Thin film of a nematic liquid crystal on an isotropic substrate. (E) Micrometer-sized metallic polyhedra folded from planar substrates. (F) A three-dimensional aggregate of micrometer plates assembled by capillary forces. Examples of static self-assemblyGeorge M. Whitesides etc, Science, Vol 295, Issue 5564, 2418-2421 , 29 March 2002Types of Self-Assembly

Examples of dynamic self-assembly


(A) An optical micrograph of a cell with fluorescently labeled cytoskeleton and nucleus; microtubules (~24 nm in diameter) are colored red. (B) Reaction-diffusion waves in a Belousov-Zabatinski reaction in a 3.5-inch Petri dish. (C) A simple aggregate of three millimeter-sized, rotating, magnetized disks interacting with one another via vortex-vortex interactions. (D) A school of fish. (E) Concentric rings formed by charged metallic beads 1mm in diameter rolling in circular paths on a dielectric support. (F) Convection cells formed above a micropatterned metallic support. The distance between the centers of the cells is ~2 mm. George M. Whitesides etc, Science, Vol 295, Issue 5564, 2418-2421 , 29 March 2002Types of Self-Assembly

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyTemplated self-assembly (T)

Types of Self-AssemblyBy combining bottom-up self-assembly with top-down patterned templates, templated-self-assembly (TSA) can provide rich opportunities for fundamental studies of self-assembly behavior in confined environments, as well as a source of innovation in nanofabrication methods.Templated Self-Assembly of Block Copolymers: Top-Down Helps Bottom-Up By Joy Y. Cheng,* Caroline A. Ross, Henry I. Smith, and Edwin L. Thomas, 2006

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyBiological self-assembly (B)Types of Self-Assembly

The shape-preserving conversion of biologically self-assembled 3-D nanoparticle structures (SiO2-based diatom frustules) into a new nanocrystalline material (anatase TiO2) via a halide gas/solid displacement reaction route is demonstrated.Anatase assemblies from algae: coupling biologicalself-assemblyof 3-D nanoparticle structures with synthetic reaction chemistryR. R. Unocic, F. M. Zalar, P. M. Sarosi, Y. Cai and K. H. Sandhage,Chem. Commun., 2004

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-AssemblyThe success of self-assembly in a molecular system is determined by five characteristics of the system:

ComponentsInteractionsReversibility (or Adjustability)EnvironmentMass Transport and Agitation

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-Assembly A self-assembling system consists of a group of molecules or segments of a macromolecule that interact with one another. These molecules or molecular segments may be the same or different. Their interaction leads from some less ordered state (a solution, disordered aggregate, or random coil) to a final state (a crystal or folded macromolecule) that is more ordered.Components

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-AssemblyAssembly by capillary forces Assembly by electrostatic forces Assembly by magnetic forces Assembly by van der WaalsAssembly by hydrophobic interactionsAssembly by hydrogen and coordination bondsInteractionsSelf-assembly occurs when molecules interact with one another through a balance of attractive and repulsive interactions.But, attention! There is no covalent bonds!

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-AssemblyAssembly by capillary forces

Capillary forces result from the interaction of liquid, gas and solid surfaces, at the interface between them.

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-AssemblyThe electrostatic interaction between electrically charged particles; the amount and direction of attraction or repulsion between two charged bodies.

Assembly by electrostatic forces

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-AssemblyAssembly by magnetic forces

When the charges are in motion, an extra force acts on them. This extra force is called themagnetic force. The magnetic force between two charges q1and q2, moving with velocities v1and v2, is equal to:

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-AssemblyAssembly by van der Waals

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-AssemblyAssembly by hydrophobic interactions

The tendency ofhydrocarbons(or oflipophilichydrocarbon-like groups in solutes) to formintermolecularaggregates in an aqueous medium, and analogousintramolecularinteractions. The name arises from the attribution of the phenomenon to the apparent repulsion between water and hydrocarbons. However, the phenomenon ought to be attributed to the effect of the hydrocarbon-like groups on the water-water interaction. The misleading alternative term 'hydrophobic bond' is discouraged.PAC, 1994,66, 1077(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))on page 1123

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-AssemblyAssembly by hydrogen and coordination bonds

Hydrogen bonding is a special type of dipole-dipole attraction between molecules, not a covalent bond to a hydrogen atom. It results from the attractive force between a hydrogen atom covalently bonded to a very electronegative atom such as a N, O, or F atom and another very electronegative atom. Hydrogen bond strengths range from 4 kJ to 50 kJ per mole of hydrogen bonds.

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-AssemblyFor self-assembly to generate ordered structures, the association either must be reversible or must allow the components to adjust their positions within an aggregate once it has formed. The strength of the bonds between the components, therefore, must be comparable to the forces tending to disrupt them. For molecules, the forces are generated by thermal motion. Processes in which collision between molecules leads to irreversible sticking generate glasses, not crystals.Reversibility (or Adjustability)

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-AssemblyThe self-assembly of molecules normally is carried out in solution or at an interface to allow the required motion of the components. The interaction of the components with their environment can strongly influence the course of the process.Environment

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-AssemblyFor self-assembly to occur, the molecules must be mobile. In solution, thermal motion provides the major part of the motion required to bring the molecules into contact.In nanoscale, mesoscopic, and macroscopic self-assembly systems, the components interact in ways that are analogous to those involving molecules. In designing such systems, the first challenge often is assuring the mobility of the components; as they become larger than molecules, Brownian motion rapidly becomes irrelevant, and gravity and friction become important. The choice of interactions between the components (that is, the choice of interactions allowing the system to approach equilibrium) is also important.Mass Transport and Agitation

Vincenzo Guarino, PhD Researcher at Institute of Composite and Biomedical Materials (IMCB) National Research Council of ItalyPrinciples of Molecular Self-Assembly

Finally


Why the molecules should join ?

The systems in nature tend to the minimum energy state

Thermodynamic


Thermodynamic Principles of Self-assemblyUnderstanding Self-assembly by using statistical thermodynamics* Association colloids or complex fluids fluid-like micelles, bilayers* Forces in micelles, bilayers - van der Waals, hydrophobic, hydrogen-bonding, screened electrostatic interactions

= N + kT log X1= 20 + kT log X2 = 30 + kT log X3 = . . .

or= N = 0N + (kT/N) log (XN/N) = constant, N= 1, 2, 3, , monomersdimerstrimers N : mean chemical potential of a molecule in an aggregate of aggregation number N 0N : standatd part of the chemical potential (the mean interaction free energy per molecule) XN : concentration (activity) of molecules in aggregates


Law of Mass Action (Alexander and Johnson, 1950)

Rate of association = k1X1N, Rate of dissociation = kN(XN/N)In equilibrium, both rates are same k1X1N = kN(XN/N) k1/kN = (XN/N)X -N

Equilibrium constant is also given by, K= k1/kN= exp[-N(0N- 01)/kT]

We can combine two equations to obtain XN = N{X1 exp[(01- 0N)/kT]}NMore generally, XN= N{(XM/M)exp[M(01- 0N)/kT]}N


Conditions Necessary for the Formation of AggregatesXN= NX1N* Aggregates formation is originated from, different cohesive energies between the molecules in the aggregate and the dispersed states (N0 < 10 )

X1 XN

self assembly technique in rigenerative medicine

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