EGRB 427 Study Guide - Quiz Guide: Polyethylene Glycol, Tricalcium Phosphate, Polyglycolide
30 Oct 2018
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Biomaterials, including both natural and synthetic, refer to any substance that is intended to interact
with
biological systems for a medical purpose-either a therapeutic (treat, augment, repair, or replace a tissue
function of the body) or a diagnostic one defined by application NOT chemical makeup
Natural biomaterials: derived from biological source
●Advantages
: availability, ecological safety, increased biocompatibility, biodegradability, and
remodeling as compared to synthetic biomaterials
●Disadvantages
: limited physical and mechanical stability (may not be suitable for load bearing
applications)
●Protein origin biomaterials → created using stem cell differentiation and transplantation, provide
structure to tissues
○silk → secreted by worms, advantages
: [low degradation rate, superior handling
characteristics], disadvantages
: [inflammation, reaction can lead to encapsulation]
○collagen → collagen sponge bone grafts: [rhBMP-2 delivery to induce de novo bone
formation], catgut sutures: [twisted strands of purified collagen from small intestine of
cattle/sheep/goats, “submucosa of sheep intestine or the serosa of bovine intestine and is
approximately 90% collagen”, absorption in 90 days, full tensile strength of >= 7 days]
○fibrin
○gelatin
●Polysaccharides origin biomaterials → usually derived from agricultural feedstock or crustacean
shell wastes, extremely bioactive, sugar monomers help maintain extracellular matrix
○hyaluronan
○alginate → alginate hydrogel microbeads: [treatment of type 1 diabetes through
encapsulation of islet cells, controlled local drug release]
○agarose
○chitosan
Synthetic biomaterials: materials made by chemical synthesis
●Advantages
: properties tailored to specific applications, cheaper than natural biomaterials, can be
easily produced in larger quantities
●Disadvantages
: lack sites for cell adhesion, may have to be chemically modified to increase this
limited bioactivity, poor inducers of tissue remodeling
●Polymer biomaterials
○PEG (poly-ethylene glycol)
○PGA (polyglycolide) → sutures (very reliable, effective for long-term wound healing)
○PLGA (poly-lactic-co-glycolic acid)
○PDLLA (poly-D, L-lactide)
○PCL (poly-e-caprolactone)
○PDO (polydioxanone) → sutures
○PGCL (polyglycolide-co-caprolactone) → sutures (not suitable for cardiovascular or
neurovascular procedures because tension decreases too fast)
●Ceramic biomaterials
○alumina
○Zirconia
○sintered HA
○α-TCP, β-TCP (alpha/beta tricalcium phosphate)
○tetracalcium phosphate
○hydroxyapatite
○bioactive glass
○calcium phosphate
●More examples of synthetic biomaterials: insulin pump, hip implant, dental implant: [crown,
abutment, dental implant (“surgical post/tooth root”)], cochlear implant: [electrical stimulation of
the brain to provide hearing, internal (cochlear implant) + external (sound processor)]
Biomaterials by Function:
●replacement: artificial hip joint
●assist in healing: sutures, bone plates, screws
●improve function: cardiac pacemaker, intraocular lens
●aid to diagnosis: probes and catheters
●aid to treatment: catheters
Development of Biomaterials
●First Generation
○beginning in 1950-1960
○bioinert, biocompatible, minimal reaction/interaction
○Ex. gold fillings, wooden teeth, bone plates, PMMA dental prosthesis, glass eyes, dacron
and parachute cloth vascular implants
●Second Generation
→
○bioactive, controlled reactions to induce therapeutic effect (e.g. bone bonding, drug
release)
○Developed by collaboration of physicians and engineers
○Included development of resorbable materials
○Ex. titanium alloy dental/orthopaedic implants, cobalt-chromium-molybdinum
orthopaedic implants, UHMW polyethylene bearing surfaces for joint implants, heart
valves, pacemakers
●Third Generation
→
○regenerative functional tissue, biointeractive, integrative resorbable, stimulate specific
cell responses at molecular level (e.g. proliferation, differentiation, ECM production and
organization)
○Ex. artificial skin, genzyme cartilage cell procedure, resorbable bone repair cements,
genetically engineered biological components (growth factors)
Third Generation Biomaterials
●Encapsulation of islet cells by modified alginates
●Tissue engineered blood vessels
How do these second/third generation implants improve on their previous counterparts?
●gold tooth vs. titanium implant → promotes osseointegration as opposed to bioinert gold tooth
●plastic vascular graft vs. tissue engineered vascular graft → tissue engineered graft promotes
remodeling of vasculature as opposed to fibrotic encapsulation of plastic grafts
Tissues are grouped into soft tissue (skin, blood vessels, cartilage, ligaments) and hard tissue (bone and
tooth). As such, implant material used in replacing tissues vary: soft (polymers), hard (metals, ceramics)
stenosis: obstruction to flow (ex. calcific aortic stenosis causes hypertrophy (enlargement) of left ventricle
because of excess pressure)
regurgitation: reverse flow across valve
Document Summary
, including both natural and synthetic, refer to any substance that is intended to interact with. Biomaterials biological systems for a medical purpose-either a therapeutic (treat, augment, repair, or replace a tissue function of the body) or a diagnostic one defined by application not chemical makeup. Natural biomaterials: derived from biological source remodeling as compared to synthetic biomaterials. Advantages : availability, ecological safety, increased biocompatibility, biodegradability, and. Disadvantages : limited physical and mechanical stability (may not be suitable for load bearing. Protein origin biomaterials created using stem cell differentiation and transplantation, provide applications) structure to tissues. Silk secreted by worms, advantages : [low degradation rate, superior handling characteristics], disadvantages : [inflammation, reaction can lead to encapsulation] Polysaccharides origin biomaterials usually derived from agricultural feedstock or crustacean shell wastes, extremely bioactive, sugar monomers help maintain extracellular matrix. Alginate alginate hydrogel microbeads: [treatment of type 1 diabetes through encapsulation of islet cells, controlled local drug release]
