Two-way Permeability of Ion Permeable Mirocapsules for Remineralization

Objectives: The objective of this study was to measure the release of calcium, phosphate and fluoride ions from microcapsules with ion permeable membranes that have been charged or recharged with aqueous salt solutions.  Methods: A heterogeneous polymerization technique was utilized to prepare a series of microcapsules with an ethylene glycol based polyurethane shell containing nanopure water or different aqueous solutions of potassium phosphate dibasic or potassium phosphate dibasic of different concentrations.  Ion release profiles of charged and recharged microcapsules were studied as a function of initial ion concentration within the microcapsule, ion concentration of the charging solution, time of exposure to the charging solution, ion identity (fluoride, phosphate, calcium) and temperature. Phosphate ion detection was performed by the molybdenum blue method.  Calcium and fluoride ion release measurements were performed using ion specific electrodes.  Results:   Ion release profiles of ions released from charged and recharged microcapsules were studied under various conditions.  A table highlighting some of the results is shown below.

Salt in the recharging solution	Concentration of charging solution	1 hour (ppm)	4 hours (ppm)	12 hours (ppm)	24 hours (ppm)
Potassium phosphate dibasic	0.4	3	10	17	22
Potassium phosphate dibasic	0.8	15	31	86	125
Potassium Phosphate Dibasic	1.6	7	14	35	59
Potassium Phosphate Dibasic	2.4	2	3	4	4
Calcium Nitrate	0.8	24	59	145	167

Conclusions: Ion release profiles were generated for charged and recharged microencapsulated aqueous solutions that contained biologically available ions useful in remineralization.  The potential for recharging the microcapsules compounded in a variety of dental formulations was demonstrated.  This work is funded in part by Premier Dental Products Incorporated, GL Materials Research LLC and an NSF University-Industry Partnership grant.