Cosmetic particulate gel delivery system and method of preparing complex gel particles

#1. Field of the Invention

#This invention relates to a novel cosmetic or dermatological delivery system having a variety of applications for delivery of topically applied active agents to the skin, to methods of preparing such delivery systems and to cosmetic or dermatological formulations in which the delivery systems may be incorporated. Of particular interest are multiphase cosmetic formulations such as gels, creams and lotions.

#One difficulty with known cosmetic delivery systems is that of protecting labile compounds from reacting prematurely. Furthermore, certain biologically active substances, e.g. alphahydroxy acids, are known to benefit the skin by improving skin softness and appearance. However, many such actives tend to cause irritation because they have the capacity, if the local concentration is too high, to penetrate deeply through the stratum corneum to more sensitive living tissue. Accordingly, there is a need for a delivery system that can separate active agents from a formulating excipient or adjuvant and provide controlled release of the active substances at the point of application. It would also be advantageous to provide a delivery system for actives that permits localized concentration of actives at the point of delivery, for instance, at the skin's surface.

#Some illustrative embodiments of the invention, and the best mode contemplated of carrying out the invention, are described in detail below with reference to the accompanying drawings in which:

#FIG. 1 is a schematic view of an embodiment of cosmetic gel particle carrier according to the invention which takes the form of an agar bead;

#FIG. 2 is a schematic view showing several of the agar beads shown in FIG. 1 being crushed on the skin of a user;

#All parts and proportions referenced in this description, unless otherwise stated, are on a weight or weight-for-weight basis.

#Referring to FIGS. 1 and 2, a particularly preferred embodiment of particulate cosmetic gel carrier comprises relatively small agar particles or agar beads 10 having an average particle size measured in millimeters. The particles are small enough for cosmetic use, and preferably do not exceed 10 mm. in diameter, on average, but not so small as to penetrate the skin or skin pores. A minimum diameter, on average, is about 0.05 mm. (50 microns). A preferred range of particle sizes is from about 0.1 to 3.0 mm. in diameter, on average, with a more preferred range being from about 0.25 mm. to about 1 mm. in diameter, on average.

#Preferred methods of producing the particles yield a well-focussed size distribution, so that it is preferred that at least 80 percent of the particles, more preferably 90 percent of the particles, lie within a desired average particle size bracket extending up to about 30 percent either side of a targeted average. If desired, for particular applications, a more uniform product can be obtained by mesh filtration.