Biomaterials PDF

Biomaterials Exam ques*ons will be simple for this lecture. What is biomaterial? - A biomaterial is a nonviable (non-living) material used in a medical device, intended to interact with biological systems. - Any material of natural or of synthe*c origin that comes in contact with *ssue b...

Biomaterials Exam ques*ons will be simple for this lecture. What is biomaterial? - A biomaterial is a nonviable (non-living) material used in a medical device, intended to interact with biological systems. - Any material of natural or of synthe*c origin that comes in contact with *ssue blood or biological fluids, and intended for use in prosthe*c, diagnos*c, therapeu*c or storage applica*on without adversely affec*ng the living organism and its components. Why do we need biomaterials? - Transplanta*on o Cri*cal donor shortage: 3000 livers annually for 30,000 pa*ents in need. o Disease transmission: HIV, Hepa**s, etc. - Surgical reconstruc*on o Not always possible o Complica*ons. - Biomaterials and *ssue engineering o Engineer new *ssues. Systems o The analysis of risks and benefits has to take into account. § Tumorigenicity, graQ rejec*on, immunogenicity, and cell migra*on. Applica7ons of biomaterials - Replacement of diseased or damaged *ssue o Orthopaedic implants, heart valve. - Assist in healing. o Medical glues, haemosta*c sponges, sutures, bone plates, orthopaedic screws. - Improve func*on. o Cardiac stent, pacemaker, orthodon*c wire Classifica7on of biomaterials based on material source. Natural - AutograQ – *ssue transplanted from another part of the body to the same individual. - AllograQ – a *ssue graQ from a donor of the same species as the recipient but not gene*cally iden*cal. - XenograQ – a *ssue graQ or organ transplant from a donor of a different species from the recipient. - IsograQ – a graQ of *ssue between two individuals who are gene*cally iden*cal. Synthe7c - Metals, ceramics, polymers, semiconductor materials. - Biocompa7bility - Ability of the material to obtain an appropriate biological response for a given applica*on in the body. Bioinert - Has minimal interac*on with its surrounding *ssue/ - E.g. stainless steel, *tanium, alumina - Fibrous capsule might form around bioinert implants → bifunc*onality relies on *ssue integra*on through the implant. Bioac7ve - Interacts with the surrounding *ssue. - E.g. hydroxyapa*te, glass ceramic. - Occurs through a *me-dependent kine*c modifica*on of the surface. Bioresorbable - Dissolved (resorbed) and slowly replaced by advancing *ssue (such as bone) - E.g. tricalcium phosphate, poly (lac*c-co-glycolic acid) copolymers. - S*tches Different types of biomaterials Metals - What we want from metal. (exam?) o Strong o Light o Non-corrosive inside human body. - Advantages o Superior mechanical proper*es o Can be prepared in various forms and textures. - Disadvantages o May corrode and release harmful metallic ions. o Dense and heavy o Not aesthe*c o Not biodegradable. - Corrosion: deteriora*on of a metal o Chemical (non-aqueous) corrosion: § Direct reac*on between the metallic and non-metallic elements in the absence of H2O/electrolytes o Electrochemical corrosion: § mostly, when two or more dissimilar metals are in direct physical contact, e.g. two adjacent or opposing restora*ons made of different alloys. Titanium and Titanium alloys: Materials of choice ✓ Good mechanical proper*es for an implant (lightweight, durable, strong and can be prepared in various forms and textures) ✓ Corrosion resistance ✓ Adsorp*on of the proteins on Ti surface ✓ Not toxic, inert, and do not cause chronic inflammatory reac*ons Why does 7tanium not corrode? - Titanium’s corrosion resistance is provided by a *ghtly adherent TiO2 film through passiva*on. - Titanium oxide is very strong therefore even though it corrode, it’s very strong, it protects *tanium underneath. Ceramics, glasses, and glass ceramics. - Advantages o ✓ Inert and superior biocompa*bility o ✓ Bioac*ve o ✓ High compressive strength and hard o ✓ Aesthe*c quali*es o ✓ Can be injectable - Disadvantages o ✓ Bri_le and not flexible o ✓ Low tensile strength o ✓ Difficult to make and form Polymers - Advantages o ✓ Resilient o ✓ SoQ (low fric*on) o ✓ Aesthe*c o ✓ Biodegradable o ✓ Easy to manipulate, form, and use o ✓ Low cost - Disadvantages o ✓ Low mechanical strength o ✓ May deform with *me and temperature o ✓ Leaching monomers Tissue engineering. - Reconstruct the diseased or damaged *ssues. - 1. Remove cells - 2. Expand number in culture - 3. Seed onto an appropriate scaffold with suitable growth factors - 4. Place into culture - 5. Re-implant engineered *ssue repair damaged site Why is 7ssue engineering necessary? - ✓ Most *ssues cannot regenerate when injured or diseased - ✓ Even *ssues that can regenerate spontaneously may not completely regenerate due to large defect and excessive *ssue strain - ✓ Replacement of *ssue with permanent implants is greatly limited, e.g limited integra*on, low rate of regenera*on What types of cells are used for TE? - ✓ Embryonic stem cells - ✓ Adult stem cells - ✓ Differen*ated cells Poten7al cell sources (differen7ated or adult stem cells) - 1. Autogene*c (autologous) cells are obtained from the same individual to which they will be reimplanted. o Immune acceptable, not off-the-shelf availability, expensive - 2. Allogeneic cells are donated to the pa*ent from another person. o Requires engineering immune acceptance, risk of disease transmission, off the-shelf availability. - 3. Xenogeneic cells are isolated from another species (non-human source animals). o Requires engineering immune acceptance, risk of animal virus transmission, off-the-shelf availability.