BIOMATERIALS
Lecture 1 Introduction to Biomaterials
What is a biomaterial?
A biomaterial is a nonviable material used in a medical device, intended to interact with
biological systems.
or
Biomaterial is any material, natural, man-made, or device that comprises whole or part of a
living organism, which performs or replaces a natural function within a living organism.
Need for biomaterials
Inability to treat many diseases, injuries and conditions with other therapies or procedures:
replacement of body part that has lost function (total hip, heart)
correct abnormalities (spinal rod)
improve function (pacemaker, stent)
assist in healing (structural, pharmaceutical effects: sutures, drug release)
Characteristics of Biomaterials Science
multidisciplinary
multi-biomaterial
clinical need-driven
substantial world market
risk-benefit issues
General applications of Biomaterials
Storage of fluids, tissues, and other biological products
Diagnosis
Monitoring
Therapy
History of biomaterials - out
Requirements of Biomaterials
A biomaterial must be:
bioinert (minimal response from host tissues) or
specifically bioactive (controlled reaction with tissues - drug delivery)
biocompatible
mechanically and chemically stable or
biodegradable
processable (for manufacturability)
nonthrombogenic (if blood-contacting)
sterilisable
What is biocompatibility?
Biocompatibility is the ability of a material to perform with an appropriate host response in a
specific application.
host response is: the defense mechanism of the host against exogenous microorganisms
the reaction of a living system to the presence of a material
A general term meaning that a biomaterial, device or construct can be brought into direct
contact with living tissue without:
causing a harmful tissue reaction (pain, swelling or necrosis)
that could compromise function;
causing a systemic toxic reaction; or
having tumourigenic potential.
Name biocompatibility testing procedures
Evaluation of:
cytotoxicity;
acute, subchronic, and chronic toxicity;
irritation to skin, eyes, and mucosal surfaces;
sensitisation;
hemocompatibility;
short-term implantation effects;
genotoxicity;
carcinogenicity; and effects on reproduction, including developmental effects.
Lecture 2 Biocompatibility - Processing and Structure
Biomaterials structure
Both synthetic materials & biological systems have many length scales of structural importance
Primary Chemical Structure (atomic & molecular 0.1-1 nm)
Primary bonding (ionic, covalent, metallic)
Secindary/Intermolecular bonding (electrostatic interactions, H-bonding, Van der Waals,
hydrophobic interactions, physical entanglement)
Biocompatibility is strongly determined by primary chemical structure!
Higher Order Structure (1-100 nm)
Crystals: 3D periodic arrays of atoms or molecules (metals, ceramics, polymers)
Networks: exhibit short range order & characteristic lengths (inorganic glasses, gels)
Self-assemblies: aggregates of amphiphilic molecules (block copolymers, micelles, lyotropic
liquid crystals)
Microstructure (1m +)
Crystal grains: crystallites of varying orientation (stainless steels)
Spherulites: radially oriented crystallites interspersed w/ amorphous phase (semicrystalline
polymers, glass-ceramics)
Precipitates: secondary phases present as inclusions (metals, ceramics, polymers)
Porosity: often desirable in biomaterials applications
Higher order structure & microstructure strongly dictate kinetic processes & mechanical
response.
Lecture 3 - Biomaterials Properties
Bulk Mechanical Properties
Types of loads
Why study mechanical properties?
Design structures (i.e. prosthetic devices for joint replacement and repair) that are safe
against the combined effects of applied forces and moments.
1. Selection of proper materials
2. Determine safe & efficient loading conditions
Tension
Tensile stress is the stress state leading to expansion (length of a material tends to increase in
the tensile direction).
Parameters measured:
engineering stress () and engineering strain ().
= Ft/A0 : Force applied perpendicular to the cross section of sample
= (li-l0)/l0: l0 is the length of sample before loading
li is the length during testing
Hookes law (1678):
A solid material subjected to a tensile (distraction) force would extend in the direction of
traction by an amount proportional to the load.
Solids behave in an elastic manner (spring) if the loads are not too great.
stress has units: N/m2 or lb/in2
Stress-Strain Diagram
Compression
Compressive stress is the stress that, when applied, acts towards the centre of a material. The
material is under compression.
Elastic deformation
Shear out
Lecture 4-5 Properties and Classes of Biomaterials
torsion, bending, creep, fatigue out
Surface Properties and Characterisation
Objectives of surface analysis:
Determine how the surface chemistry (and therefore, properties) differs from the bulk
(relative to the function of the material in the device, effects on the body, and response
to effects on the body).
Identify contaminants (with respect to effects of the material on the body).
Identify chemical bonding possibilities for interactions with molecules in the
biological milieu with respect to the effects of the material on the body (bioadhesion)
and the body on the material.
Biological Response to Contact with Materials:
Biological response: A study of the molecular and cellular events that follow contact with
biological fluids or tissues whether in vitro or in vivo, from initial contact to the eventual
culmination of the response.
The biological response to implanted biomaterials and devices is controlled by their surface
chemistry and structure.
Surface modification allows to influence the bio-interaction while retaining the key
physical properties.
Surface modification possible using:
Biological methods
Mechanical methods
Physicochemical methods
Biological Response sequence of local events following device implantation out
Main Types/Classes of Biomaterials
The three main types of biomaterials and their medical applications (examples) are:
(1) Polymers: ear parts, facial prosthesis, dentures tracheal tubes, esophagus, lung/kidney/liver
parts, heart components, pacemakers, blood vessels, knee/bone/finger joints, sutures, scaffolds
for tissue engineering, drug delivery
(2) Metals: stents, heart valves, cranio-maxillofacial implants, orthopeadic knees/hips and
bone/joint replacement, oral/dental implants, surgical instruments, external prostheses
(3) Ceramics: In orthopeadics as bone plates and screws, hip components (i.e. femoral heads),
knee prostheses, coatings (of metal prostheses) to control implant/tissue response, filling of
diseased bone. In dentistry as crowns, bridges, implants, caps, brackets. Other uses are inner
ear implants (cohlear implants), drug delivery devices.
(Others: glass etc.)
(4) Glasses?
(5) Composites?
Hydrogels Biomedical Applications
Biomedical use due to bio- and blood-compatibility
Pharmaceutical use due to hydrophilicity (controlled/sustained drug release)
Earliest biomedical application contact lenses
o good mechanical stability
o favorable refractive index
o high oxygen permeability
o needs hygienic maintenance
o unable to correct for astigmatism
lubricating surface coating
o used with catheters, drainage tubes and gloves
o non-toxic
Biodegradable Polymers
Why would a medical practitioner like a material to degrade in the body?
Do not require a surgery for removal
Avoid stress shielding
Offer tremendous potential as the basis for controlled drug delivery
Degradation Schemes
Medical Applications of Biodegradable Polymers
What is Tissue Engineering?
Tissue engineering is the use of a combination of cells, engineering materials,
and suitable biochemical factors to improve or replace biological functions.
INDUSTRIAL MICROBIOLOGY
Lecture 6-7 - Introduction to Industrial Microbiology
What is Industrial Microbiology?
Industrial microbiology is the study of the large-scale and profit motivated
production of microorganisms or their products for direct use, or as inputs in the
manufacture of other goods.
Characteristics of an industrially important microorganism
An industrially important microorganism must:
Produce the product of interest quickly and in high yield.
Grow rapidly on inexpensive culture media available in bulk
quantities.
Be amenable to genetic manipulation.
If possible, be nonpathogenic.
History of Industrial Microbiology out
Lecture 8-9 Fermentation Systems and Beverage Fermentations
Factors affecting the wine spoilage
Acidity - the lower the pH the less likely the wine will spoil. Molds, yeasts, acetic acid
bacteria would not be stopped by any pH normal to wines: pH 3.5-4.0 (most wines);
Sugar content < 0.1%;
Ethanol content .14%
Temperature - spoilage most rapid at 20-30oC.
Lecture 10 - Food Fermentation
Contribution of the Fermented Foods
enrichment of the human dietary
preservation of food to hinder (delay) the growth of food spoilage microorganisms
enrichment of nutritional value of food (vitamins, proteins, essential amino acids etc)
detoxification of food (lectins, phytates etc)
a decrease in cooking time and fuel requirements
Lecture 11 Environmental Biotechnology
Biological oxygen demand (BOD)
Chemical oxygen demand (COD)
Treatment methods:
Parameters used in deciding on the most appropriate method of wastewater treatment: flow
(m3/day), BOD (mg/L), TSS (mg/L), TS (mg/L), temperature, pH, total nitrogen, phosphate
and other specific pollutants (along with variations that occur in these parameters over a
given period of time)
Factors that influence the final choice of treatment plant:
land availability, overall construction and operating costs, performance requirements (e.g.
percentage BOD/COD removal) and the human resources needed to run the plant
Options for the treatment of wastewaters include:
biological treatments:
aerobic and/or anaerobic processes
chemical treatments:
coagulation, flocculation, precipitation and electrochemical processes
physical treatments:
screening, sedimentation or incineration
One or more of these methods can be used based on the wastewater characteristics
Stages of biological wastewater treatment plant
(domestic sewage or industrial wastewaters):
primary treatment
preliminary treatments and primary sedimentation
Purpose: to remove settlable organic solids
Efficiency: BOD removal - 30% (30 - 40%)
SS removal - 60% (50 - 70%)
primary sedimentation design criteria:
surface loading rate (SfLR)
the volume (m3) of wastewater added to each m2 surface area of the tank per day
(range 3045m3/m2/day)
solids loading rate (SoLR)
the quantity of TSS added to each m2 surface area of the tank per day
(range of 235kg TSS/m2/day)
operating hydraulic retention time (HRT) or mean residence time
normally only 16 h (odour formation due to the formation of anaerobic metabolites)
secondary treatment
aerobic or anaerobic biological treatment and secondary sedimentation
Purpose: to remove soluble organics
Efficiency: BOD removal - 90% (85 - 95%)
SS removal - 90% (85 - 95%)
suspended homogeneous systems:
activated sludge process and anaerobic stirred tank reactor
attached film processes:
aerobic and anaerobic trickle filters
ENZYME KINETCS
Lecture 12 - Introduction to Enzymes
Lecture 13 Michaelis-Menten Kinetics
You need to know the whole lecture
Lecture 14 Enzyme Kinetics and Inhibition
I am expecting you to know the whole lecture
Lecture 15 Enzyme Activity Enzyme Kinetics
Lecture 16 Enzyme Kinetics Examples
I am expecting you to know the whole lecture
