Korean J Urol Oncol.  2017 Dec;15(3):178-186. 10.22465/kjuo.2017.15.3.178.

Poloxamer 407 Hydrogels for Intravesical Instillation to Mouse Bladder: Gel-Forming Capacity and Retention Performance

Affiliations
  • 1Drug Delivery Research Lab, College of Pharmacy, Chung-Ang University, Seoul, Korea. ywchoi@cau.ac.kr
  • 2Department of Urology, College of Medicine, Chung-Ang University, Seoul, Korea.
  • 3Immunotherapeutics Branch, Research Institute, National Cancer Center, Goyang, Korea.

Abstract

PURPOSE
Poloxamer 407 (P407) thermo-sensitive hydrogel formulations were developed to enhance the retention time in the urinary bladder after intravesical instillation.
MATERIALS AND METHODS
P407 hydrogels (P407Gels) containing 0.2 w/w% fluorescein isothiocyanate dextran (FD, MW 4 kDa) as a fluorescent probe were prepared by the cold method with different concentrations of the polymer (20, 25, and 30 w/w%). The gel-forming capacities were characterized in terms of gelation temperature (G-Temp), gelation time (G-Time), and gel duration (G-Dur). Homogenous dispersion of the probe throughout the hydrogel was observed by using fluorescence microscopy. The in vitro bladder simulation model was established to evaluate the retention and drug release properties. P407Gels in the solution state were administered to nude mice via urinary instillation, and the in vivo retention behavior of P407Gels was visualized by using an in vivo imaging system (IVIS).
RESULTS
P407Gels showed a thermo-reversible phase transition at 4℃ (refrigerated; sol) and 37℃ (body temperature; gel). The G-Temp, G-Time, and G-Dur of FD-free P407Gels were approximately 10℃-20℃, 12-30 seconds, and 12-35 hours, respectively, and were not altered by the addition of FD. Fluorescence imaging showed that FD was spread homogenously in the gelled P407 solution. In a bladder simulation model, even after repeated periodic filling-emptying cycles, the hydrogel formulation displayed excellent retention with continuous release of the probe over 8 hours. The FD release from P407Gels and the erosion of the gel, both of which followed zero-order kinetics, had a linear relationship (r²=0.988). IVIS demonstrated that the intravesical retention time of P407Gels was over 4 hours, which was longer than that of the FD solution ( < 1 hour), even though periodic urination occurred in the mice.
CONCLUSIONS
FD release from P407Gels was erosion-controlled. P407Gels represent a promising system to enhance intravesical retention with extended drug delivery.

Keyword

Poloxamer 407; Intravesical delivery; Thermo-sensitive hydrogel; Bladder simulation model; In vivo imaging system

MeSH Terms

Administration, Intravesical*
Animals
Dextrans
Drug Liberation
Fluorescein
Hydrogel*
Hydrogels*
In Vitro Techniques
Kinetics
Methods
Mice*
Mice, Nude
Microscopy, Fluorescence
Optical Imaging
Phase Transition
Poloxamer*
Polymers
Urinary Bladder*
Urination
Dextrans
Fluorescein
Hydrogel
Hydrogels
Poloxamer
Polymers
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