Biomaterials - 2 PDF

BIOMATERIALS HAMZA ALI 014  TABLE OF CONTENT 2nd 01 INTRODUCTION 04 GENERATION 1970s - 2000 HISTORICAL 3rd 02 BACKGROUND 05 GENERATION 2000...

BIOMATERIALS HAMZA ALI 014  TABLE OF CONTENT 2nd 01 INTRODUCTION 04 GENERATION 1970s - 2000 HISTORICAL 3rd 02 BACKGROUND 05 GENERATION 2000 - present 1ST 03 GENERATION 1950s - 1960s INTRODUCTION BIOMATERIALS biomaterial:-A synthetic material used to replace part of living system or to function in intimate contact with living tissue Biomaterials and biological material are not the same thing !!! Biological material:- a substance produced by a living organism naturally Synthetic material that only comes in contact with the skin such as hearing aids and bandages are generally not classified as biomaterials  HISTORICAL BACKGROUND  The practical use of biomaterials didn’t become possible until the promotion of aseptic surgical techniques in the 1860s After that the first use biomaterials were focused in the field of skeletal system (orthopedic) In the 1900s bone plates were used to fix long bone fractures but these plates failed due to poor mechanical designs. Earlier materials chosen primarily for their mechanical properties often corroded rapidly in the body and produced toxic substances inhibiting the natural healing process of the body e.g VANADIUM STEEL In 1930s introduction of stainless steel and cobalt chromium alloys led to greater success in fracture fixation and performance of the first ever joint replacement surgery After WW2 retained fragments of plastic from aircraft canopies didn’t trigger an adverse side effect in injured pilots leading to the use of plastics and polymers as biomaterials  1st GENERATION OF BIOMATERIAL S GENERAL CHARACTERISTICS These 1st gen biomaterials were specifically designed for use inside the human body and saw application in multiple disciplines of medicine e.g orthopedics, cardiovascular surgery, ophthalmology, wound healing These were based on commonly available materials CELLULOSE ACETATE:- used to make the early dialysis tubes DACRON:- used as early vascular grafts These materials although did help in treatment of disease but produced serious inflammatory responses therefore newer materials were selected on the basis of 2 characteristics  BIOCOMPATIBLITY BIOFUNCTIONALITY Refers to the acceptance of the of an Refers to a biomaterials ability to artificial implant by the surrounding exhibit enough physical and tissue and the body as a whole mechanical properties to augment or replace body tissue A completely biocompatible would not cause thrombogenic, toxic, A material used for bone inflammatory response or exhibit augmentation should exhibit a high carcinogenic, mutagenic, teratogenic compressive strength effects A material used for ligament No synthetic material is completely augmentation should a high degree of biologically inert flexibility and tensile strength CLASSIFYING BIOMATERIALS BIOMATERIALS NATURAL SYNTHETICS Biomaterials can be classified on the basis of their origin Note that there is a significant overlap in the categories of the biomaterials and may also apply to newer generations of biomaterials NATURALLY OCCURRING BIOMATERIALS All biomaterials of non human origin are called naturally occurring cellulose catgut ivory silk Natural rubber glass graphite Several pure metals Catgut was used as a suture materials Natural rubber was used to develop synthetic grafts  METALS AND ALLOYS Metals are commonly used for load bearing implants specifically orthopedic procedures utilize variety of metals to replace and augment skeletal functions e.g screws, plates, joint prosthetics Metals are also used in cardiovascular surgery, dental implants, maxillofacial implants The disadvantage of lies in the biocompatibility characteristics as the metals tend to corrode over time within the body Corrosion leads to disintegration of implant and release of harmful substances into the surrounding tissue PURE METALS Gold, sliver, platinum represent some of the earliest used metals as biomaterials due to their tissue compatibility and corrosion resistance Metal ligatures and silver slips are used during surgery to control bleeding Pure metals have been replaced by metals alloys Infact since 1940 only one new pure metal is introduced as biomaterial TITANIUM  ALLOYS An alloy is a mixture of two or more metals, or a metal and another element, combined to enhance properties like strength or durability. The first metal alloy developed for human use was vanadium steel (it corrodes inside humans) The most commonly used alloys are stainless steel, titanium alloys, cobalt based alloys STAINLESS STEEL 18-8 TYPE 18-8sMo TYPE Also called 302 stainless steel Also called 316 stainless steel 18% chromium- 8% nickel 18% chromium- 8% nickel, sMo= molybdenum Another type called 316L stainless steel L= low carbon content The 316 and 316L together are called austentitic stainless steels and are the most widely used alloys as biomaterials TITANIUM ALLOYS Titanium and its alloys are widely used as biomaterials due to their biological inertness and superior mechanical properties Titanium is a reactive metals that forms an oxide layer on its surface when exposed to air, water, specific electrolytes This oxide layer provides a protective coating protecting the metal from chemical degradation and biological environment And since this oxide layer is insoluble it doesn’t release ions in the surrounding tissues SHAPE MEMORY ALLOYS (SMAs) A group of alloys that have interesting property of thermal shape memory, superelasticity, force hysteresis. Force hysteresis:- Imagine squeezing a stress ball. When you release your grip, it doesn't expand back to its original size immediately. Instead, it takes a moment to regain its original shape. That delay is an example of force hysteresis. NITINOL an alloy of nickel and titanium is the most widely used SMA. used in endovascular stents, intracranial aneurysm clips, and vascular suture anchors.  CERAMICS Ceramics are polycrystalline compounds including silicates, metallic oxides, carbides, and various form of refractory hydrides, sulfides, selenides The first clinical application of ceramic was the use of plaster of paris as casting material. Generally ceramics are brittle and have low tensile strength making their use limited as a biomaterials. However recently new hightech ceramics have been introduced that have high bioinertness and high strength These implantable ceramics are called bioceramics and are grouped into 3 categories bioceramics Biodegradable Bioinert ceramics Bioreactive ceramics ceramics BIOINERT CERAMICS These are non-absorbable carbon-containing ceramics,alumina, zirconia and silicon nitrides These maintain their mechanical and physical properties inside the host They are used in dense porous forms, usually having a good wear, and are excellent for gliding function E.g bioinert ceramics are used to produce femoral head replacements They are used as structural support implants such as bone plates and bone screws BIOACTIVE CERAMICS (2nd gen) These are also called surface reactive ceramics These biomaterials have the ability to provoke surrounding bone and tissue responses which makes it advantageous for anchoring an implant or reducing its stress. Bioreactive ceramics include glass, glass ceramic, calcium phosphate based materials They can be used as coatings, continuous layers, embedded particles in orthopedic amd dental surgery. BIODEGRADABLE CERAMICS (2nd gen) Also called resorbable ceramics These include aluminum calcium phosphate, coralline, plaster of paris, hydroxyapatite, tricalcium phosphate Due their porous structure they can stimulate tissue ingrowth and offer potential to fill bridge defects. They are soluble thus they can be degraded by surrounding tissue.  POLYMERS Polymers consist of small repeating units (monomers) joined together to form long chain molecules. If you ↑the molecular weight of the polymer chain = polymer becomes longer and less mobile Resulting in more rigid material If you substitute the backbone carbon with divalent oxygen of the polymer chain = this ↑ the rotational Freedom of the chain making a more flexible material If you ↑ the size of side chains / branches / cross-linking = decreases melting temperature of the polymer Polyvinyl chloride polymethylmethacrylate polyesters resins (PVC) (PMMA) Polyethylene (PE) Polystyrenes (PS) Polyamides / polysiloxanes nylons Polypropylene (PP) Fluorocarbon polymers Polyurethanes The above mentioned are the widely used polymers These can be used in implantable devices, coatings, catheters, tubings, vascular grafts, injectable drug delivery, imaging systems  COMPOSITES Composites are composed of two or more distinct materials attaining the desired physical and chemical property of material incorporated E.g rubber catheter is often filled with very fine particles of silica to enhance strength and toughness  2ND GENERATION OF BIOMATERIAL S  GENERAL CHARACTERISTICS While biofunctionality and bioinertness remain important properties of a biomaterials the newer generation of the biomaterials are more focused on bioactive and biodegradable properties BIOACTIVE BIODEGRADABLE These materials exhibit specific These materials exhibit clinically and controlled interaction with relevant breakdown and the surrounding tissue absorption Allows functional tissue to grow and replace it  BIODEGRADABLE POLYMERS The biodegradable polymers degrade in the body allowing functional tissue to grow in its place The degradation can be hydrolytic or enzymatic Biodegradable polymers natural synthetic  NATURAL BIODEGRADABLE POLYMERS Starch chitin collagen glycosaminoglycan SYNTHETIC BIODEGRADABLE POLYMERS Polyglycolic polyactides polycaprolactone poly(ortho)esters polyanhydrides polyphosposphaz acid anes Biodegradable polymers are used in sutures, wound dressings, fracture plates, screws, controlled drug delivery systems. Biodegradable matrices and scaffolds show great deal of promise in the field of tissue engineering  HYDROGELS These are cross-linked hydrophilic polymer network that can absorb water or other biological fluids Swelling behaviour:- the material's ability to absorb water due to its structural network properties Diffusive characteristics:- refer to their ability to allow the diffusion of molecules, such as drugs or nutrients, through their matrix. This property is essential in applications like drug delivery systems, where controlled release of substances is desired. Surface properties:- hydrogels have complex surface structures composed of many dangling chains. Hern and Hubbell incorporated adhesion promoting oligopeptides into hydrogels, giving them the ability to mediate cell adhesion properties.Similarly, by using modified lipid bilayers, hydrogel surfaces have been engineered to mimic cell membranes  The first ever hydrogel used was to make contact lenses Hydrogel are very useful in controlled drug delivery systems by altering their diffusive characteristics. There are two methods of this Reservoir system:- the agent/drug is stored in a central core surrounded by hydrogel layer Matrix system:- the agent/drug is uniformly distributed throughout the material and slowly released from it BIOACTIVE AND BIODEGRADABLE CERAMICS ALREADY EXPLAINED BUT KEEP IN MIND THEY ARE PART OF THE 2ND GENERATION  3RD GENERATION OF BIOMATERIAL S GENERAL CHARACTERISTICS These materials are both biodegradable and bioactive They can aid regeneration not only replacement of injured and lost tissue These use nanofabrication and microfabrication techniques These new biomaterials are “smart” biomaterials that can detect and respond to various tissue and cellular stimuli  TISSUE ENGINEERING AND BIOMATERIALS the process of creating living, physiological, three-dimensional tissues and organs utilizing specific combinations of cells, cell scaffolds, and cell signals, both chemical and mechanical is called tissue engineering There are three ways to use biomaterials in this field 1. To induce cellular migration or tissue regeneration 2. To encapsulate cells and act as an immunoisolation barrier 3. To provide a matrix to support cell growth and cell organization  To induce cellular migration and tissue regeneration Use of bioactive biomaterial to facilitate local tissue repair and promote cell movement to the site of implantation These materials are designed in such a way that they release a variety of chemicals, proteins, growth factors in controlled fashion through either diffusion or network breakdown E.g 1. infusion of bone morphogenic protein into orthopedic implants 1. Use of glycosaminoglycan and collagen construct to act as an artificial skin substitute  Immunoisolation barrier for encapsulated cells To escape a immune response when foreign cells are introduced inside the body an immunoisolation barrier is required E.g 1. Hollow fiber membranes enclosing hepatocytes have been used to construct and bioartificial liver for treatment of liver failure 2. Microcapsules have been developed to store and protect the transplanted cells A matrix to support cell growth and cell organization This is the most widespread use of biomaterials in tissue engineering A matrix usually called a scaffold is used to direct 3-dimensional organization of cells in vitro and vivo SCAFFOLD:- these are porous structures created from natural or synthetic polymers, they come in variety of forms like sheets, fabrics, gels. Recent scaffolds are embedded with growth and proliferation factors allowing yhem to regenerate tissue  NANOTECHNOLOGY AND BIOMATERIALS Nano fabrication refers to the process and methods employed in the creation of Nanoscale materials and structures Nanofabrication techniques utilize top down and bottom up fabrication methods top down fabrication methods are such as electron beam lithography Dental Fillings: Nanocomposite materials containing nanoparticles of silica or other reinforcing agents are used in dental fillings. These materials improve the mechanical properties and durability of fillings while matching the natural color of teeth. Diagnostic Imaging: Iron oxide nanoparticles are used as contrast agents in magnetic resonance imaging (MRI) to improve the visualization of tissues and organs. These nanoparticles can be functionalized with targeting ligands for specific imaging of tumors or diseased tissues. THANK YOU