CHAPTER

11Materials forBiomedicalApplications

Biomaterials: Material intended to interface with biological systems to evaluate, treat, augment, or replace any tissue, organ, or function of the bodycf) Biological Materials

Biocompatibility 1. composition of biomaterials2. fabrication process3. implant production

1.1.2 History and Current Status of the Field

Plastics [poly(methylmethacrylate)] to Metal, Ceramic, Polymer

(1)Cardiovascular areaheart valvesynthetic vascular graft

(2) Artificial Joints

(3) Heart-lung machines

blood oxygenation limit blood coagulation problem

(4) Renal dialysis

blood cell lysisinfectionimmune response

1.1.3 Future Directions

inert biomaterialsbioactive materials

smart or instructive materials injectable materialsnano-structured materials

Biomaterials for complete integration

and full reproduction of damaged tissue

1.2 Biological Response to Biomaterials

inflammation, immune response, blood clotting, infection, tumor formation, implant calcification

Factors to be considered for biocompatibility

type of materialsshape of the implantmaterial degradation characteristics surface chemical properties bulk chemical and mechanical properties

the final location and application of the implant

protein and cellular response (in vitro and in vivo)

1.3 Biomaterial Product Testing and FDA Approval

Safe and effective FDA approves devices, not materials

1.4 Types of Biomaterials

1.4.1 Metalsnon-directional metallic bonds with highly mobile electrons

1.4.2 Ceramics non-directional ionic bonds between electron donors and acceptors

--- hard and nondegradable but brittle

1.4.3 Polymers directional covalent bonds

synthetic polymerspolymers from natural sources

1. Elastomers

2. Hydrogels

3. Composite materials

human tissues

1.4.4 Naturally Derived vs. Synthetic Polymers

Naturally Derived Polymers

1. full integration2. easy remodeling 3. limited amount available4. low mechanical properties 5. pathogenic contamination 6. immune response7. biomaterials of decellularized tissue

Synthetic Polymers

1. mass production and sterilization 2. physical, chemical, mechanical, and degradative properties 3. no tissue interaction 4. low healing 5. low chance of human application

1.5 Processing of Biomaterials

(1) surface modification to alter the surface chemical and physicalproperties

(2) shape

1.6 Important Properties of Biomaterials

1.6.1 Degradative properties

undesirable for implantation desirable for certain materials (biodegradable materials)

1.6.2 Surface properties

chemical and physical properties

1.6.3 Bulk properties

(1) mechanical properties : strength and stiffnessanisotropyfatigue property

(2) Physical properties crystallinity thermal transition

(3) Chemical propertieshydrophobicity

1.6.4 Characterization Techniques

Quantitative and Qualitative

1.7 Principles of Chemistry

1.7.1 Atomic structure proton, neutron, electron amu: atomic mass units

1.7.2 Atomic models

electrons: particle-like and wave-like qualities

1.7.3 Atomic Orbitals

Quantum numbers: size, shape, and orientation of the electron probability functions

1. Principal quantum number2. Azimuthal quantum number 3. Magnetic quantum number4. Spin quantum number

(1) Shapes of subshells

(2) Order of subshells and the Aufbau principle

1. Lower energy states filled first 2. Pauli exclusion principle (two electrons with opposite spin) 3. Hund’s rule

1.7.4 Valence Electrons and the Periodic Table

Closed-shell configuration and open-shell configuration Valence electrons: primary bonds like ionic and covalent bonds

1.7.5 Ionic Bonding

Bonding and Force-distance Curves

1.7.6 Covalent Bonding

(1)Atomic orbitals and hybridization

(2) Molecular orbitals

and bonds

(3) Mixed bonds

Ionic bonds ------------- Covalent bonds

1.7.7 Metallic Bonding

Electropositive elements without electronegative elements to accept electrons

Mobile electron cloud or sea Electron sharing but non-directional Mobility of electrons --- conductivity

1.7.8 Secondary Forces

Dipole-dipole interaction

Temporary (fluctuating) dipoles: van der Waals interaction

Permanent dipoles: hydrogen bonds