Formation and closure of microchannels in skin following microporation.
OBJECTIVE
To characterize the microchannels created in hairless rat skin by microneedles and investigate their closure following exposure to different occlusive conditions.


METHODS
Maltose microneedles were characterized by scanning electron microscopy. The microchannels created and their closure when exposed to different conditions was investigated using a variety of techniques.


RESULTS
Microscopic imaging indicates a pyramidal geometry of maltose microneedles with an average length of 559 ± 14 μm and tip radius of 4 μm. Upon insertion into skin, they created microchannels with an average surface diameter of 60 μm and an average depth of 160 ± 20 μm as observed by histological sectioning and confocal microscopy. Skin recovers its barrier function within 3-4 hrs, and microchannels closed within 15 hrs of poration when exposed to environment. However, when occluded, the microchannels remained open for up to 72 hrs in vivo, as observed by calcein imaging, transepidermal water loss measurements and methylene blue staining.


CONCLUSIONS
Maltose microneedles penetrated the stratum corneum barrier and created microchannels in skin which completely close within 15 hrs after poration. However, under occluded conditions, barrier recovery can be delayed for up to 72 hrs in vivo.
Kalluri
Haripriya
H
Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Mercer University, 3001 Mercer University Drive, Atlanta, Georgia 30341, USA.
Banga
Ajay K
AK
D000818:Animals; D016503:Drug Delivery Systems / Q000295:instrumentation / Q000379:methods*; D066298:In Vitro Techniques; D007271:Injections, Intradermal; D007700:Kinetics; D008297:Male; D008320:Maltose / Q000737:chemistry; D008845:Microinjections / Q000295:instrumentation / Q000379:methods*; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D009339:Needles; D010539:Permeability; D051381:Rats; D054772:Rats, Hairless; D012867:Skin / Q000378:metabolism / Q000648:ultrastructure*; D012995:Solubility; D013499:Surface Properties; D013997:Time Factors
D008320:Maltose