Biomaterials as long as Tissue Replacements Evolution of Biomaterials Biological Responses to Biomaterials Biomaterials is a $9 Billion business in the U.S. Polymers: many repeating parts
DavidNYC,, Contributing Editor has reference to this Academic Journal, PHwiki organized this Journal MSE 536: Introduction to Advanced Biomaterials Fall, 2010 Dr. R. D. Conner A biomaterial is a material intended to interface with biological systems to evaluate, treat, augment or replace any tissue, organ or function of the body Biocompatibility The ability of a material to per as long as m with an appropriate host response in a specific application Host Response The response of the host organism (local in addition to systemic) to the implanted material or device. Marrow stem cells could heal broken bones, Betterhumans Newly grown kidneys can sustain life in rats, Bio.com Doctors grow new jaw in man’s back, CNN FDA approves implanted lens as long as nearsightedness, CNN Stent recall may raise quality expectations, Medical Device Link Examples of Biomaterials in the News
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The REPIPHYSIS® works by inserting an exp in addition to able implant made from titanium in an aerospace polymer into the childs healthy bone, after which st in addition to ard recovery in addition to rehabilitation are expected. However, instead of undergoing repeated surgeries to extend the bone, the REPIPHYSIS® uses an electromagnetic field to slowly lengthen the implant internally. Romans, Chinese, in addition to Aztecs used gold in dentistry over 2000 years ago, Cu not good. Eyeglasses Ivory & wood teeth Aseptic surgery 1860 (Lister) Bone plates 1900, joints 1930 Turn of the century, synthetic plastics came into use WWII, shards of PMMA unintentionally got lodged into eyes of aviators; Parachute cloth used as long as vascular prosthesis 1960- Polyethylene in addition to stainless steel being used as long as hip implants A brief history of biomaterials Biomaterials as long as Tissue Replacements Bioresorbable vascular graft Biodegradable nerve guidance channel Skin Grafts Bone Replacements
A few examples composite foam seeded with bone marrrow stromal cells Contact Lens Bileaflet heart valve prosthesis Image of vascular grafts constructed of exp in addition to ed poly-tetrafluoroethylene (Teflon) Image of blood clots on a bileaflet heart valve Problems with heart valves: Mechanical failure Blood clotting Tissue overgrowth An orthopedic hip implant, exhibiting the use of all three classes of biomaterials: metals, ceramics in addition to polymers. In this case, the stem, which is implanted in the femur, is made with a metallic biomaterial. The implant may be coated with a ceramic to improve attachment to the bone, or a polymeric cement. At the top of the hip stem is a ball (metal or ceramic) that works in conjunction with the corresponding socket to facilitate motion in the joint. The corresponding inner socket is made ot of either a polymer ( as long as a metallic ball) or ceramic ( as long as a ceramic ball) in addition to attached to the pelvis by a metallic socket.
Schematic of a heart-lung machine setup. Potential Problems: High resistance in filter leads to high blood pressure Low oxygenation efficiency Anticoagulants necessary to prevent clotting Cell matrices as long as 3-D growth in addition to tissue reconstruction Biosensors, Biomimetic , in addition to smart devices Controlled Drug Delivery/ Targeted delivery Biohybrid organs in addition to Cell immunoisolation New biomaterials – bioactive, biodegradable, inorganic New processing techniques Advanced in addition to Future Biomaterials Evolution of Biomaterials Structural Functional Tissue Engineering Constructs Soft Tissue Replacements
Biological Responses to Biomaterials Biocompatibility: Incompatibility leads to: inflammation redness swelling warmth pain Other reactions include: immune system activation blood clotting infection tumor as long as mation implant calcification Protein in addition to cellular response determine success of an implant The road to FDA approval Approval Steps: In vitro testing (in glass) In vivo testing w/healthy animals In vivo testing w/animal models of disease Controlled clinical trials Biomaterials is a $9 Billion business in the U.S. Over 100,000 Heart Valves 300,000 Vascular grafts 500,000 Artificial Joints
Common Applications as long as Materials Polymers Metals Ceramics Polymers fall into three categories: Elastomers (e.g. rubber b in addition to s) Composites Hydrogels (absorb/retain H2O) Polymers Polymers may be natural or synthetic Natural polymers are derived from sources within the body: collegen, fibrin, hyaluronic acid (from carbohydrates), or outside: chitostan (from spider exoskeletons) or alginate (from seaweed) Chitostan & alginate are used as wound dressings
Polymers: many repeating parts Chemical structure of poly (methyl methacrylate), a polymer commonly used as a bone cement. (a) shows a section of the polymer chain, with the dotted lines indicating the repeating unit, which is also shown in (b) Advantages & Disadvantages of Natural Polymers Advantages: Chemical composition similar to material they are replacing: easily integrated into host in addition to modifiable Disadvantages: Difficult to find in quantity Low mechanical properties Non-assurance of pathogen removal May be recognized as as long as eign by immune system Advantages & Disadvantages of Synthetic Polymers Advantages: Easily mass produced in addition to sterilized Can tailor physical, chemical, mechanical in addition to degradative properties Disadvantages: Do not interact with tissue in an active manner, thus cannot direct or aid in healing around implant site Few have been approved by FDA
Biomaterial Processing Techniques developed to change surface chemistry while leaving bulk material unchanged; e.g.: ceramic coatings on hips, coating a catheter with antibiotics Important Properties Interaction between material & host Degradative: affected by the shape, size, in addition to bulk chemical, physical in addition to mechanical properties Corrosion: pH Surface properties: biological response affected by proteins adsorbed to surface. Surface chemistry affects adsorption Important Biomaterial Property: Wetting Wetting is a measure of a fluids ability to spread out on a solid substrate Hydrophobicity is a measure of a materials attraction to water. If it is hydrophobic it is water fearing in addition to does not wet; if it is hydrophilic it is attracted to water in addition to spreads
The Chemistry of Materials The Bohr atomic model, which separates the atom into a nucleus (containing protons in addition to neutrons) in addition to orbiting electrons. For an electrically neutral atom, the positive charge of the nucleus is balanced by an equal number of electrons. In this model, electrons are depicted as orbiting the nucleus in discrete energy states, or orbitals, which are separated by a finite amount of energy. The energy an electron looses by moving from an outer to an inner shell is released as a photon, with energy E = hn The distribution of the hydrogen electron as depicted by both the (a) Bohr in addition to (b) the wave-mechanical models. However, in the wave-mechanical model, orbitals are thought of as the probability that an electron will occupy a certain space around the nucleus in addition to they are characterized by probability functions. Depiction of the energy states as long as the 2p subshell. Because each subshell has a characteristic shape as determined by the electron probability functions (dumbbell-shaped as long as p subshells), the different energy states are represented by identical subshells oriented along different axes (x, y in addition to z) The relative energies of shells in addition to subshells as long as all elements. Note that the lower the shell number, the lower the energy (e.g., energy associated with 1s is less than as long as 2s). Additionally, the energy of the subshells in each shell increases from s to f. However, energy states can overlap between shells (e.g., energy of the 3d shell is greater than the 4s).
Order of filling electron orbitals The Periodic Table of Elements Atomic bonding Tm = depth of well E = d2U/dr2 a is proportional to the asymmetry in the potential well Ft = Fa + Fr U = Ft dr
21 Compounds: Often have similar close-packed structures. Close-packed directions -along cube edges. Structure of NaCl STRUCTURE OF COMPOUNDS: NaCl Diamond, BeO in addition to GaAs are examples of FCC structures with two atoms per lattice point
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