MacLean-McDavitt DS, Robertson JD, Jay M. Monitoring the in vivo delivery of proteins from carbomer hydrogels by X-ray fluorescence.
Pharm Res 2003;
20:435-41. [PMID:
12669965 DOI:
10.1023/a:1022612422769]
[Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE
To measure the effect of protein size on their disappearance from subcutaneously implanted carbomer hydrogel matrices.
METHODS
A series of different molecular weight (MW) proteins were iodinated, incorporated into Carbopol hydrogels, injected subcutaneously into rats, and monitored using X-ray fluorescence (XRF).
RESULTS
A 10 mg/mL minimum concentration of Carbopol-940 was necessary before protein 150 mg/mL iodinated bovine serum albumin (I-BSA)] retention times increased with increasing hydrogel concentration. The decreasing protein signal was not caused by outward protein diffusion or iodoprotein hydrolysis. As the protein MW increased, protein retention times lengthened [e.g.. 6.2 h for insulin (5.7 kDa) to 13.3 h for thyroglobulin (669 kDa)]. Protein disappearance was monophasic first-order for some proteins and biphasic first-order for others. The disappearance rate constant ranged from 0.093 +/- 0.005 h(-1/2), to 0.187 +/- 0.057 h(-1/2), indicating gel erosion rather than protein diffusion as the rate-limiting mechanism. Entrapped I-BSA in Carbopol-1342 NF. pH 7.4, and Carbopol 2001-ETD, pH 7.4, gel matrices yielded different disappearance rates and profiles than Carbopol-940. The overall 50% disappearance rate of I-BSA was greatest for Carbopol-1342 NF (41 +/- 8 h), followed by Carbopol-2001 ETD (25 +/- 2 h) and Carbopol-940 (10.5 +/- 0.7 h).
CONCLUSION
XRF is a noninvasive technique that can be used to follow the status of macromolecules in vivo.
Collapse