Uptake and cytotoxicity of chitosan molecules and nanoparticles: effects of molecular weight and degree of deacetylation.
OBJECTIVE
To evaluate the effects of molecular weight (Mw) and degree of deacetylation (DD) on the cellular uptake and in vitro cytotoxicity of chitosan molecules and nanoparticles.


METHODS
Chemical depolymerization and reacetylation produced chitosans of Mw 213,000 to 10,000 and DD 88-46%, respectively. Chitosan was labeled with FITC and transformed into nanoparticles by ionotropic gelation. Uptake of chitosan by confluent A549 cells was quantified by fluorometry, and in vitro cytotoxicity was evaluated by the MTT and neutral red uptakeassays.


RESULTS
Nanoparticle uptake was a saturable event for all chitosan samples, with the binding affinity and uptake capacity decreasing with decreasing polymer Mw and DD. Uptake fell by 26% when Mw was decreased from 213,000 to 10,000, and by 41% when DD was lowered from 88% to 46%; the uptake data correlated with the zeta potential of the nanoparticles. Uptake of chitosan molecules did not exhibit saturation kinetics and was less dependent on Mw and DD. Postuptake quenching with trypan blue indicated that the cell-associated chitosan nanoparticles were internalized, but not the cell-associated chitosan molecules. Chitosan molecules and nanoparticles exhibited comparable cytotoxicity, yielding similar IC50 and IC20 values when evaluated against the A549 cells. Cytotoxicity of both chitosan entities was attenuated by decreasing polymer DD but was less affected by a lowering in Mw.


CONCLUSIONS
Transforming chitosan into nanoparticles modified the mechanism of cellular uptake but did not change the cytotoxicity of the polymer toward A549 cells. Chitosan DD had a greater influence than Mw on the uptake and cytotoxicity of chitosan nanoparticles because of its effect on the zeta potential of the nanoparticles.
Huang
Min
M
Department of Pharmacy, National University of Singapore, 18 Science Drive 4, Singapore 117543.
Khor
Eugene
E
Lim
Lee-Yong
LY
D000107:Acetylation; D000277:Adjuvants, Pharmaceutic / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity; D048271:Chitosan; D004337:Drug Carriers; D004705:Endocytosis / Q000187:drug effects; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D018613:Microscopy, Confocal; D008970:Molecular Weight; D036103:Nanotechnology; D010316:Particle Size
D000277:Adjuvants, Pharmaceutic; D004337:Drug Carriers; D005456:Fluorescent Dyes; D002686:Chitin; D048271:Chitosan; D016650:Fluorescein-5-isothiocyanate