Figure 6.

LbL nanoparticles have long refrigerated shelf lives as indicated by the preservation of their size, uniformity and charge characteristics. Ten different LbL particles consisting of a carboxy-modified latex core and a bilayer of poly(L-arginine) and a unique polyanion were stored for three months at 4 degrees Celsius. (a) We compared the hydrodynamic number average size for the particles after storage and compared them to the particle’s original size. With the exception of the Fucoidan-coated particle, all others maintained statistically consistent sizes during storage. (b) These particles likewise exhibited statistically consistent polydispersity index, suggesting that particle uniformity is maintained during storage. (c) The z-average size measurement, which is more sensitive to aggregates, demonstrated that 7 out 10 formulations exhibited statistically consistent sizes during storage. (d) Generally, the zeta potential of the nanoparticles was conserved during storage with a few exceptions. Sulfated beta cyclodextrin-coated particles exhibited a significant charge increase during storage. On the other hand, hyaluronic acid and dextran sulfate-coated particles exhibited a small, but statistically significant decrease in zeta potential. Overall these data indicate that LbL particles would be amenable to months-long refrigerated storage without concern of loss of colloidal stability. One-way ANOVA with the Bonferroni post-test (alpha = 0.01) was used to determine statistical significance between the indicated samples.