microneedles Flashcards
(15 cards)
what advantages does drug delivery via microneedles have compared to oral and injection dosage forms
oral drugs: may have poor absorption, drug degradation in GI and liver
injection: painful and hard to use for patients themselves
microneedles, painless, ease of use by patients themselves, safer needle disposal eliminate spread of pathogens by reusing needles
how do microneedles deliver drugs
penetrate stratum cornerum into viable epidermis
- avoids contact with nerve fibres and blood vessels (in dermal later)
drug delivered here allowing movement from demise into body
4 types of MN
solid, coated, dissolving, hollow
MAIN: solid and hollow
what is photolithography
method of making silicone microneedles where light is used to etch shape of needles
describe the process of fabrication of solid microneedles
combo of photolithography and micro moulding
silicone mould made using photolithography and then this is filled using polymer melt or liquid monomers that are UV cureable
how are hollow microneedles made
uisng reactive ion etching or electroplating using master mould (electrochemical decomp of metal)
hollow microneedle fabrictaion:
describe the process in electoplating using a master mould
- tapered holed are laser drilled through polymer to form mould
- conductive later is deposited on side walls and top of mould
- metal (usually nickel) electroplated onto seed layer
- polymer mould removed to release metal hollow microneedles
hollow microneedles:
benefit and drawback of using two photon stereolithography
high resolution
more complex geometrical figures can be created
slow process means mass production is difficult
solid microneedles: how do they work
insert and remove microneedles to form microneedle pores in skin
drug can be applied to the skin to allow slow diffusion of drug through pores and into body
how do drug coated microneedles work
microneedles have been sprayed or dipped into drug needed
microneedles inserted into skin and drug is left behind
what are considerations needed when administering a drug using coated microneedles
MNs need sufficuent mechanical strength
controlled wetting and spreading of drug solution on microneedles
adhesion between drug and microneedle for insertion into skin
coating excipients should be safe
compatibility with drug
limitations of coated microneedles
small dose
loaded cargo may weaked MNs resulting in low penetration ability
considerations for drug encapsulated MNs
sufficient mechanical strength
thermosensitive should be encapsulated at moderate conditions
speed of dissolution determines the time microneedles need to be inserted into skin
what are hydrogel forming microneedles
where the drug is loaded into the backing membrane allowing sustained drug release
polymer swells as it takes up inerstitial fluid allowing drug permeation into skin
rate of drug delivery can be tuned by crosslink density in materual
advantaged and disadvantages of using hollow microneedles for infusion of liquid into skin
ad:
- control over amount and timing of drug
- separation of microneedles from drug during manufacturing
- use existing liquid formulations
dis:
- required drug reservoir, pump, microfluidic networs = expensive
