Exam 2 Flashcards
With regards to the FBR, how does the acute phase of inflammation differ from the chronic phase?
Initiated by injury to blood vessels
Self assembly of fibrinogen, forms provisional matrix. allows cells into damaged area.
protein adsorption
complement activation
macrophage activation and WBC recruitment and Neutrophil!!
-most abundant WBC, phagocytic, chemotactic. unclear what happens to them, only beginning to understand role in FBR
Neutrophils are the biggest difference
activated macrophages never disappear
no resolution of wound
FROM REVIEW:
chronic involves persistant mac. recruitmant, granulation tissue formation, fibrous encapsulation
How does complement sustain inflammation
Answer from review:
C3A, C5A proteins diffuse away from gradient and macrophages are activated (complement sustains FBR) which cause leaky vessels.
Macrophages come down to surface and phagocytize things on surface. Take proteins to present to b-cells. White blood cell trafficking. Cause leaky vessels. which allows more macrophages to continue to bind.
What are the general functions of macrophages in the FBR?
To kill, cleanup and tissue remodeling
eliminate dust, allergens, and microorganisms.
clearance of pathogens and toxins
bone resorption
recognition and removal of enteric pathogens, tolerance to food antigens and microbiota
antigen capture and presentation to B cells
phagocytosis and antigen presentation
secrete molecules that recruit other macrophages, result in the proliferation of endothelial cells and fibroblasts - they drive the foreign body response
- the more activated the greater the foreign body response
phagocytosis, recruitment of other macrophages, stimulation of fibroblasts and endothelial cells, stimulate ECM production
Phagocytic, recognize bound antibodies and complement coated foreign bodies.
Where do macrophages come from?
all macrophages have early origins. one is from yoke sack (stem cells), the second from fetal liver.
Also derived from bone marrow and then from monocytes!!!!!, activated monocytes.
All tissues have resident macrophage populations
What are three general secretory products of macrophages
there’s 5…
Diverse Secretions
1 toxic oxygen-deprived products (superoxide, H2O2, hydroxy radicals, singlet oxygen)
2 Digestive Enzymes (plasminogen or neutral proteases)
3 Monocyte Chemoattractant Protein (MCP-1)
4 Proinflammatory Cytokines: TNF-alpha, a cytotoxic moleucle. Interleukin-1 beta, stimulates fibroblast prliferation. Transforming growth factor beta (TGF-beta), induces cell death and increases…. (follow up)
How do fibroblasts participate in the FBR
Cell type that secretes ECM and secretes angiogenic factors to rebuild tissue
Motile cells that are found in tissues whose primary function is to maintain tissue integrity by responding to injury, inflammation or forces by making ECM
change tissue based on changing loads
involved in chronic phase of FBR
express more actin and myosin-myofibroblastic phenotype
overproduce ECM-responsible for fibrous encapsulation
fibrous encapsulation
What roles does collagen play in the FBR?
structural components of all connective tissues natural hemostatic and regenerative biomaterial
Collagen-structural components of all connective tissues natural hemostatic and regenerative biomaterial, cartilage bone tendons ligaments fascia skin
collagen is the molecule that makes up the fibrous capsule around the implant - collagen is an ECM molecule secreted by fibrobalsts in the late stage of the FR which makes up the fibrous capsule
Describe (list) thee different types of devices chronically implanted in the CNS
Recording Brain electrodes, --to detect epilipsy -to map activity Deep Brain stimulating Electrodes -Pacemaker like battery, stimilutates certain spots to help release certain neurotransmitters Aneurysmal Clip -used to clamp aneurysms in the brain Sustained Delivery System (wafers) -Eventually degrade, -elate chemotherapeutic drugs Cell Encapsulation device -diffuses lacking neurotransmitters to the correct spot in the brain.
Describe a typical experimental approach for studying the tissue reaction to a device placed in brain tissue
Prepare Clean and Sterile Implant Select Target tissue Select Animal Model (Select the N) Set the time points of analysis Analyze retrieved implant 1. Select Hisotological approach 2. Use Quantification 3. Statistical Analysis
Describe how you would detect and image cells specific to brain tissue using immunohistochemistry.
antibodies that targets things only expressed by a specific cell, in this case the brain
GFAP: glial fibrillary acidic protein - Astrocyte Biomarker (Unique to brain)
ED-1 (CD68): Iysosomal protein-Activated Macrophage Biomarker
NeuN: neuronal nuclie-Neuron Biomarker
Non-specific biomarkker for cell nuclei
DAPI: 4’,6-diamidino-2-phenylindole
Marks all cell nuclei
Primary IHC:
- Target a cell-specific marker with an appropriate antibody against that cell-specific marker
- The antibody has a fluorophore or alternative marker that can be imaged
Secondary or Indirect IHC
- Target a cell-specific marker with an appropriate primary antibody against that cell-specific marker
- Target the primary antibody with a secondary antibody that binds the primary
- The secondary antibody has a fluorophore or alternative marker that can be imaged
Describe how to perform indirect immunohistochemistry
Uses antibodies
Primary antibody recognizes target molecule
bind to the surface
buffer washes away all unused primary antibodies
secondary antibodies are labeled with a color or flourescent marker.
Secondary antibodies interact and bind w/ primary antibodies
Using 2ary antibodies, the signal is magnified
Describe the three sectioning planes used in histology
follow up. check w/ Tresco
Coronal-deli meat slices
Horizontal- cutting along the length of the brain
Sagittal-cuting along length and into plane of the board
CORONAL PLANE:
Vertical sectioning, dividing object into posterior and anterior portions
The SAGITTAL PLANE:
Vertical sectioning, dividing object into left and right
HORIZONTAL PLANE
Horizontal sectioning dividing object into top and bottom
Describe the general features of the foreign body response to an implanted electrode in rat brain
!!!
- Activated Macrophages @ interface both on device and tissue (inflammation) (CD68)
- Leaky blood brain barrier
- hypotrophic response in GFAP protein-fibrous encapsulation.
- NeuN indicates loss of neurons, which are never regenerated near FBR
Shape of the FBR Mirrors Implant Geometry
Activated macrophages @ abiotic/biotic surface drives FBR
activated macrophages secrete TNF-alpha, ROI’s, Proteases, Growth Factors, IL 1-beta, MCP-1 which do not diffuse easily through brain tissue.
24 hours after implantation, brain shows sign of hemorrhage
Tissue loss associated w/ array implantation likely caused by vascular damage
REVIEW: IgG-shows leaky vessels
Provide a plausible hypothesis for why the FBR is very localized at the interface of an implanted electrode;
Activated macrophages occupy the biotic/abiotic interface and behave as a delivery system and modulate tissue remodeling. Macrophages secrete a lot of things (cytokines), and they match the geometry of the implant, which means the FBR is also centered around implant.
little extracellular space so mac. secretions don’t diffuse very far
Why do you think high density penetrating electrode arrays, like the UEA, create lesions in rat cortex following implantation?;
The brain is highly vascularized which makes it extremely unlikey that the UEA could be inserted without vascular damage.
cannot put one of these in without damaging blood vessels which leads to large amount of hemorrhaging which then causes the tissue loss
REVIEW: damaged vasculature
Why does the UEA behave like a sustained release device for proinflammatory cytokines?;
With macrophages dominating the surface interface, there are proinflamatory cytokines that are constantly being released near or around the implant.
How would you redesign the UEA to reduce the impact of the FBR? Justify your design solution.
This is an opinion, think about it critically. and answer
limit surface areas, , coat w/ anti inflammatory stuff, reduce the number of spikes, just have same multiple measuring points on fewer spikes.
With regard to this course, what is meant by the term “healthcare-associated infections? and provide a synonm
Nosocomial Infections
-Infections that are acquired while receiving medical treatment in a healthcare facility
-from ‘nosos’ greek for disease
- results from introduction of bacteria during device insertion or an implant procedure or from attachment of organisms to an indwelling device, and subsequent proliferation on its surface.
-most are bacterial infections
- good clinical practice (aseptic or sterile technique) reduces but does not eliminate the occurrence of infection.
-
List three common bacteria found on the surface of the human body
staphylococcus epidermidis
staphylococcus aureus
streptococcus mitis
streptococcus salivarius
streptococcus mutans
enterococcus faecalis
streptococcus pneumoniae
streptococcus pyogenes
neisseria sp.
neisseria meningitis
Why are humans and their pets sources of bacterial contamination?
Skin is primary source of infection. 1.5 g of skin shed per day, which are covered in bacteria. Every human activity leads to skin flaking off, as it flakes off, it spreads bacteria.
animals and even plants shed cells
List 4 general strategies to prevent device related infections
Minimize contact- clean room conditions
kill everything in contact-sterilization
minimize binding at contact-surface coating
kill after contact- anti-infective coatings
What air handling filter specification should you use in building a surgical suite or a cell culture laminar flow hood?
(Number of particles removed/ cubic foot)
.3 micron air filter
room ought to be ventilated by an efficient bag filter or high efficiency particulate air filter (HEPA) system
What implants design element is likely to result in infection? and why?
Breaching of skin barrier. PERCUTANEOUS Anything that allows entrance to the body from the outside. Lack of soft tissue interface. more than 2 weeks = 50% infection
when chemotheruaputic drugs reduce the production of immune system.
What are the three most commonly infected biomedical devices?
- Foley Catheter-associated urinary tract infections
- Central Venous Catheter-assosicated bloodstream infection (High chance of morbidity)
- Ventilator Tube- associated pneumonia
most infections are extralumenal (rarely is the source of infection the infusate)
Using a foley catheter as an example explain why it gets infected if it remains in place for several weeks?
Skin particles flake off, and the bacteria is flaking off under the gown/covers. Bacteria flakes onto tube and eventually gains access to the body.
(MORE TRUE) Most infections come from bacteria from the GI tract. Patients excrete, and it’s spread over skin near butt/catheter. Bacteria gains access to body by catheter (on exterior). Bacteria in fluid swim upstream. form biofilm, can clog catheter
-Bug (E. Faecalis) crawls up, uses proteases to break down epithelial cells, enters blood streams
Why is CLABSI a more serious infection than CAUTI
CAUTI=(Catheter-associated Urinary Tract Infections)
CLABSI=(Central LIne-associated Blood Stream Infections) -major cause of morbidity and mortality in US
-Bacteria are from upper torso of body
CLABSI causes Sepsis- proinflammatory cytokines are released to all of the organs in the body. has access to blood stream and infects everywhere
What is meant by the term biofilm? and why are they especially problematic?
Polysaccharide secretion of bacteria (ECM)-negatively charged
Biofilms form on implanted devices. Ca2+ cross links and forms a barrier which excludes antibodies, complement cells and antibiotics. Once biofilm forms, an implant must be removed.
What is meant by the term sterilization? List the two most common commercial sterilization processes and their killing mechanism?
Def: a process used to render a product free from VIABLE microorganisms (absence of living organisms)
Sterility Assurance Level (SAL): Probablility of a vaiable microorganism being present on the product unit after sterilization and generally accepted max 10-6 (one in one million is nonsterile)
Dry heat ( uses destructive oxidation) Steam(autoclaving) (pressurized steam) Ethylene Oxide (1) Radiation (2)-gamma ray
look up killing mechanism
Why is it important a clean a device before sterilization?
!!!
Even dead bacteria can illicit the FBR, The mere presence of biological material will lead to the FBR.
Endotoxins (part of bacterial cell wall (graham negative) aka liposaccharides). activate macrophages and cause inflammation–even dead bacterial will increase FBR
sterilization doesn’t get rid of surface ENDOTOXINS
Explain what is meant by the term “surface coating technology”
Surface coating technology is a coating applied to biomedical devices designed to protect and enhance the surface functionality. It is important to the biomedical industry because it will impact the functionality of your biomedical device and can be tailored to fit needs of the device.
engineering the surfaces of devices to improve function of device. Alter surface properties (chemistry of a device)
Why is surface coating technology preferred in the biomedical device industry?
- modify and improve existing device
- keep majority of manufacturing processes and facilities in place
- piggyback on previous regulatory approvals
Surface coating enhances to safety and efficacy of the device without completely changing the device. These allow companies to modify and improve existing devices, keep a majority of current bulk manufacturing processes & facilities and piggyback on previous on previous regulatory approvals.
List the characteristics of an ideal surface coating?
Improves device biocompatiabliltiy
reduces adhesion of proteins, cells or microbes
durable/stable
uniformly covers the surface
is compatible w/ standard sterilization techniques
easy to apply
does not add excessive costs to the manufacturing process
does not raise additional regulatory issues
Describe two different methods used to influence protein binding at interfaces and provide a rationale for how each of them is believed to function?
Gas Plasma (vacuum) or Corona Treatment(atmospheric) -
Surfactant Adsorption
Electrostatic Based, Layer by Layer deposition
- adding positive and negative charges to the starting substrate
- eventually diffuse through material
Covalent Immobilization
What is meant by the term plasma treatment? How does it work?
Surface treatment made using an ionized gas such as Ar, O2,
Gas runs through cathode/anode becomes energized (may add particulates) and added to a coating)
so reactive they don’t remain on the surface for very long. Can add oxygen to any surface
Plasma treatment is a surface treatment made using a gas ionized under a vacuum and is used to remove contaminates, temporarily energize the surface, and add new molecular groups to the surface.
REVIEW: difference between plasma and corona. PLASMA USES VACUUM
What is meant by the term “adsorption or surfactant based coatings? How is it used as surface modifying agent?
- uses Amphiphilic molecules
- -Hydrophobic region adsorbs to hydrophobic biomaterial
- -hydrophilic region orients toward water.
Add these surfactants to the surface of biomaterial, ideally they’re covalently bonded to change surface chemistry. Permanently effects surface chemistry
What is an application weakness of adsorption or surfactant based surface treatments?
If coatings aren’t covalently bonded to device, the coating may react with things in the body, or diffuse from the surface of the device into the body. Not great long term. can be replaced by other adsorbant species.
What is meant by the term covalent surface immobilization and what are its advantages over surfactant based techniques?
Covalent surface immobilization refers to a method used to coat a surface by using covalent bonds. The primary advantage over surfactant based techniques is the in the bonding strength of the covalent bond which far exceeds that of surfactants which are linked primarily via weaker hydrophobic interactions. Advantage #2 is that the immune response is not as great
Covalent surface immobilization is a method used to layer a surface with a new molecule covalently bonded to it. It’s advantages over surfactant based techniques include a covalently bound molecule, which proves to be much stronger than surface adhesion.
What is meant by the term steric repulsion?
explained with polyehtylene oxide - steric hindrance - long chain covered with polyethylene oxide, cannot absorb so there is repulsion, physically exclude something from its space because it moves or is there - glycocalyx- polysaccahride chains covered in water that as the move around they create a space that proteins cant enter- long chain hydrophilic molecules like PEO polymer chains adsorbed or covalently attached can move at elevated temperatures and exclude proteins from interacting with the more hydrophobic biomaterials.
This occurs when the size of groups within a molecule prevent chemical reactions that would be able to occur in smaller molecules. Bringing together atoms has an energy cost as the electron clouds overlap.
Steric repulsion is the resistance to protein adsorption using steric hindrance of bound surface molecules.
REVIEW: physical barrier, molecule takes up space which prevents things from adsorbing. the molecules move and creates a wider steric repulsion zone. Focus on dynamic movement of molecules on surface
ex. PEO-binds water. surface coating technology
What is PEO and how is it employed in surface coating technology?
Polyethylene Oxide. O along polymer backbone allows H-bonding w/ H2O. Works best in fluid filled tissues (blood stream)
uses:
-increase solubility of hydrophobic molecules
-Lubricant
-Adhesion resistant coating.
repulses things sterically
Explain what is meant by the term “site specific delivery”? Why is it advantageous in the context of an antimicrobial coating?
Definition-Locating active agents or drugs only at the surface of or in the vicinity of the device;
Preferable to administering the same drugs systemically;
Local administration from the device surface concentrates the drug at the precise site where it is needed;
Decreases potential for bacterial resistance;
Avoids systemic side effects.
Chronic Dosing is the Limitation with Site Specific Drug Delivery
Effective delivery
Must deliver appropriate agents to kill off the specific pathogens that infect different devices;
Sufficient amounts of the agent released from the device need to rise to a therapeutic level;
Duration of release must be appropriate for the condition.
Site specific delivery is the act of locating active agents or drugs only at the surface of or in the vicinity of the device. It is advantageous to antimicrobial coating because it administers drugs in a systematic fashion, decreasing the potential for bacteria resistance.
Decreases bacterial resistance, avoids systemic side effects
Within the context of biomaterials, what is meant by the term hollow fiber?
Semipermeable tubular materials made of synthetic or natural materials that are capable of conducting flow in an axial direction or providing a conduit to guide tissue regeneration or isolate cells.
semipermeable: cabable of separating things
List several important biomedicl applications of hollow fiber membranes?
Liquie sterilization -cell culture .4 microns Excretory assist devices -dialysis -liver assist devices -blood gas exchangers Implantable biosensors vascular grapfts nerve repair
Describe the working principle behind hemodialysis?
!!!
Process of removing toxic molecules from blood (uremic toxins)
3 sessions of 4 hours/week
Blood flows in to dialyzer and is cleaned using the process of diffusion and ultrafiltration
-extracellular fluid=dialysate
(probably should follow up)
REVIEW image: Describe biomaterial/working principle:
blood comes from artery-pumped through dialysis membrane-dialysate pumped in the other direction. filtration by diffusion.
lots of blood contact through tubing.
How is membrane permeability determined?
Determined by pressurized flow filtration assays. Using fluorescently-labeled dextrans, performance is determied due to their low non-specific binding to mebrane of different molecular weights.
Molecular weight cut off (MWCO): MW @ which 90% are retained by membrane
Sieving assay’s
sieving curve!! graph..
What is meant by the term phase inversion?
Controlled precipitation: the proces used to form hollow fiber membranes.
wall is porous, structure traversed by an interpenetrating pore network or channels across the wall structure
-densest part of the wall is called the skin.
Generally speaking, how are hollow fibers made?
thermoplastic
-most common: PS, PAN,
process: Dry, jet wet spinning, a phase inversion technique
polymer taken and put into solution. Ran through spineret, creates hollow fiber
air gap
solvent=DMSO
nonsolvent=water
(check slides for image)
REVIEW
as soon as solvent/nonsolvent make contact at spout of spinneret they begin to form
pump of solution and nonsolvent meet in spineret. nonsolvent inside.
What types of equipment and reagents are required for fabricating a semipermeable hollow fiber?
A polymer w/ sufficient MW and solution density (15-25% w/v): so there is enough chain length to provide chain entanglement after precipitation
- A solvent for the polymer
- A miscible non-solvent
spinneret
tubular form is created w/ a spinneret.
Provide a definition for the term “elastomer” and provide two examples of the most commonly used materials in this class.;
A natural or synthetic polymers that returns rapidly to approximately its initial dimensions and shape after substantial deformation and release of its stress
Real 1: polyurethane
Real 2: Silicone
also: natural rubber(latex)
Elastin
latex exam gloves medical tubing grafts, pacemakers, balloon catheters, joint sockets for prosthetics heart assist devices condoms wound care products
Explain why isocyanates are very reactive.
def: a functional group that contains 1 N, 1 C, 1 O.
because they’re so electronegative, the have a very reactive resonance structure. highly reactive, reacts with nucleophilic amines and …? (nucleophilic addition)
Outline the basic reactions that underlie the formation of a polyurethane oligomer (synthesis);
!!!!!!
Synthesized as thermosetting polymers
copolymers that exhibit elasticity
Diol+2 Diisocynate = prepolymer
prepolymer+chain extender=copolymer
Diol:
MW betwen 1000-2000 Da,
2 types used, polyester based (susceptible to hydrolytic degradation) or polyether based
chain extenders:
add amorphous region called soft segment
glycol, gloycol, butanediol, glycerol
Provide a structural model that explains the structure/ properties relationship of a typical segmented thermoplastic polyurethane
Polyeurethane linkage is also susceptible to hydrolysis. Not cleaved due to aromatic components which are hydrophobic. they resist the attack.
monomer diol–diisocyanate – monomer diol
|||| |||||||
hard segment ————————-soft segment
||||||||||
randomly segmented copolymer
Soft Segment-free rotation increases elasticity and the amorphous microstructure
Hard Segment-aromatic pi bonding increases crystallinity and hardness
Explain why some thermoplastic polyurethanes are susceptible to degradation in the bodily tissues.
Urethane linkages are susceptable to degradation
In the context of this course, define what is meant by the term “silicone” and provide an example of one?
Technical name is polysiloxane-incorrectly labeled in 20’s.
R-Si-R
|
O
definition: an inorganic compound with repeating Si-O linkages in the backbone where silicon is also bonde to organic groups.
Linear silicones are fluids at room temp.
mostly thermosetting elastomers
R=Methyl group
PDMS !!!
Describe in general terms a synthetic scheme for a silicone and explain why they are difficult to reprocess.
Step 1: Polymerization -platinum-based addition reactions (free radical) --either-- -Condensation reactions
Step 2: Cross-Linking
-no crystalinity-behaves like carbon-behaves like large saturated hydrocarbon chain-amorphous regions of polymer cross linked at random
Thermosets cannot be re-melted or reformed because they’re cross linked. like thermoplastics and must be mixed from a two part liquid silicone that contains cross linker and catalyst
Due to second step.
Provide three examples of biomedical devices made from poly(siloxanes).
Joint replacement
Cosmetic/Plastic
- breast implants
- lap bands
- testicular prosthectis
- butt implants
Lubricants for biomedical devices
hyodermic needles
Medical device encapsulation or used in mold making
-pace maker
Condoms
tubing, check valves, gaskets, respirator mask,
-Hand joint replacement
List three attributes of poly(siloxanes) that make them a favorite material for biomedical devices.
Extremely soft and pliable, easily conform to different cavity shapes;
High gas permeability;
Low reactivity with tissue and body fluids;
Good tensile strength and tear resistance (generally lower than polyurethanes);
Susceptible to degradation in acidic conditions (i.e. stomach);
Hydrophobic (protein adsorption);
Easily sterilized under all conditions.
How does a central venous catheter differ from a peripherally inserted central catheter or PICC?
def of catheter: tubes that can be inserted into a body cavity, duct, or vessel that allows drainage, administration….
two most common complications are infection/thrombosis
PICCS:
centrally placed, tip ends up in Superior Vena Cava
Peripherally inserted meant it goes into your body at your elbow and threaded into vein
May have a valve at the tip, preventing blood from backing up into the catheter, so heparin is not necessary
can do most normal activities, expcept swimming, or other extreme arm movements
difference:
length and where tip ends up!
