Yuanyuan Liang

Study on the electrostatic and piezoelectric properties of positive polypropylene electret cyclosporine A patch

Corona charged electrets at voltages of +500 V, +1000 V and +1500 V were prepared for manufacturing polypropylene (PP) electret blank patches and PP electret drug patches. The stability of external electrostatic field of the electret patch and the polarization of the drug in patch under the internal electrostatic field of the electret were studied. The results indicate that all the electret drug patches had good charge storage stabilities. However, the non-electrode coated electret drug patch had better stability in the external electrostatic field than that of the electrode coated electret drug patch. The higher the charging voltage of the electret, the faster the surface potential of the electret drug patch decayed, and the worse the stability of the external electrostatic field. All the electrets used in this study could result in the polarization of the model drug in patch. The piezoelectric properties of non-electrode coated electret drug patch increased with the charging voltage of the electret. However, excessively higher charging voltage could result in the decreased polarization of the drug in patch. Both the stability of the external electrostatic field of electret and the polarization of drug were the key factors for controlled drug release and skin permeation.

Enhanced transdermal delivery of cyclosporine a by PP electret and ethyl oleate

Transdermal delivery of high molecular weight compound is a great challenge due to the barrier function of the skins outer stratum corneum (SC) layer. The aim of the present work was to characterize in vitro transdermal delivery of cyclosporine A through rat skin and the drug transdermal enhancing effect of PP electret applied individually and in combination with chemical enhancer. The permeated cumulative amount and steady state flux of the cyclosporine A were determined in following situations: (a) under application of PP electret, (b) after application of ethyl oleate, (c) combination PP electret and ethyl oleate. All the techniques could enhance cyclosporine A transdermal delivery. The combination of PP electret and ethyl oleate proved to be the most effective technique.

Studies of penetration of electrostatic field of electret through skin and its stability

Skin is composed of epidermis, dermis and subcutaneous tissues. The outmost layer of the epidermis, stratum corneum, is considered the main physical barrier to water evaporation from our body and drug transdermal delivery. The SC is 15µm in thickness and is composed of proteins and lipids in which protein-rich corneocytes are surrounded by lipid bilayers [1].

Optimizing the formulation of cyclosporine A electret patch and the controlled release of drug

The polypropylene (PP) film coated with/without aluminum electrode were charged with the gird voltages of −500 V, −1000 V and −2000 V to prepare the electrets and produce electric field for control of drug release. The model drug of cyclosporine A (CsA) was loaded on a patch and ethyl oleate was used as the chemical enhancer in the manufacturing process. The formulation of the CsA drug patch enhanced by chemical was optimized, and the in vitro release behaviours of drug in the patches were studied to explore the enhancing effect of the external electrostatic field on the CsA release from the patch. Besides, the piezoelectric d33 coefficient was also determined to study the polarization of the drug in the patch under the action of the internal electrostatic field of the electret. The results indicate that the electrostatic field produced by the electret could polarize the drug in patch and enhance the release of CsA from the patch, and the effect depended on the electrode coating condition and charging voltage of the electret.

Enhancing effect of negative polypropylene electret on in vitro transdermal delivery of cyclosporine A solution and its synergistic effect with ethyl oleate

In this study, the corona charged electrets at voltages of −500 V, −1000 V and −2000 V were made from polypropylene (PP) film. The cyclosporine A (CsA) and 10% ethyl oleate were chosen as the model drug and chemical enhancer, respectively. The charge storage stability of the electrets and the in vitro transdermal behaviour of the model drug in solution under different conditions were studied. The results indicate that the external electrostatic field of the negative PP electrets could penetrate through the rat skin and enhance the transdermal delivery of cyclosporine A. A synergistic effect on enhancing the transdermal delivery of cyclosporine A was observed by combining different surface potential negative PP electrets with 10% ethyl oleate, and the amount of transdermal delivery of CsA was greatly increased comparing with only application of electrets. Therefore, the combination application of electret and chemical enhancer could be a feasible strategy in enhancing transdermal delivery of small peptide drugs or some large molecular drugs.

Thermal analysis for studies of electret states of rat skin

The open thermally stimulated discharge (TSD) and differential thermal analysis (DTA) were employed to study the electret state and its forming mechanism of the rat skin. The appearance of one dipole peak and two space charge peaks in open TSD current spectra indicated that skin is an excellent natual electret. Corresponding to the TSD spectra, three typical phase transition were detected in DTA spectra at about 63°C, 82.7°C and 115.1°C, respectively. The lamellar lipid structure, collegan network structure and protein space structure are the main explanation of the formation of skin electret state. Besides, hydration in skin will strengthen the electret effect of the skin.