Preparation And Application Of Alginate Microspheres Encapsulating L-Ascorbic Acid

In this paper, alginate microspheres encapsulated L-ascorbic acid (named as Vc-ALGmicrospheres) were prepared by emulsification/internal gelation technique with the objectiveof improving it stability and then applied in cosmetics. Firstly, on the basis ofquantificationally studying the stability of L-ascorbic acid in different conditions andchoosing the proper film material of alginate microspheres, one-factor and response surfacemethod were carried out to get the optimized conditions of alginate microspheresencapsulated L-ascorbic acid, taking encapsulation efficiency(EE) of L-ascorbic acid andparticle sizes of alginate microspheres as indexes. To improve the EE further, themicrospheres were prepared using sodium alginate (ALG)/N,O-carboxymethyl chitosan(NOCC) as wall materials under the optimized conditions(named as Vc-ALG/NOCCmicrospheres). Then the Vc-ALG/NOCC microspheres were coated with chitosan (named asCS-Vc-ALG/NOCC microspheres) to make the microspheres resistance to environment andexpand the application of microspheres.Stability test of L-ascorbic acid shows that under the acidic or neutral or ultrapure water,light-avoiding, low-temperature and no oxygen condition, L-ascorbic acid is stable and itspreservation rate is still above90%in24hours. Sodium alginate with G/M ratio2.01isselected as the experimental material.The optimized conditions were obtained through use of response surface methodpresented in Design-Expert8.0.6. Results show under optimized conditions: dosage of span802%(mass of the oil); volume fraction of water30%; stirring rate400rpm; massconcentration of sodium alginate18.80g·L-1; mole ratio, n(acetic acid): n(CaCO3)=3.29:1;mass ratio, w(Ca): w(ALG)=7.16%. Under the conditions, the EE of Vc-ALG microspheresis63.83%.N,O-carboxymethyl chitosan was prepared by the two-step alkalization method withchitosan as raw material, in order to improve the water-solubility of chitosan. Under theoptimized conditions, using ALG/NOCC as wall materials, the EE of Vc-ALG/NOCCmicrospheres is77.08%, which is1.2times of Vc-ALG microspheres.And Vc-ALG/NOCCmicrospheres have less pores in the surface than Vc-ALG microspheres by the scanningelectron microscope (SEM). Product performance test shows that L-ascorbic acid propertiesdon’t change, keep good stability, and have the abilities of DPPH radical scavenging andtyrosinase inhibition rate, which prove that properties of antioxidant and whitening don’tchange. The encapsulation process is physical entrapment.The prepared CS-Vc-ALG/NOCC microspheres were added to skin creams. Theaccelerated aging test shows that the cream can resist to low and high temperature. Efficacyevaluation results show that cream with CS-Vc-ALG/NOCC microspheres has a certain effectto improve skin moisture, reduce moisture loss and melanin deposition.