Transdermal Properties of Cell-Penetrating Peptides: Applications and Skin Penetration Mechanisms

Cell-penetrating peptides (CPPs) consist of 5-30 amino acids with intracellular transduction abilities and diverse physicochemical properties, origins, and sequences. Although recent developments in bioinformatics have facilitated the prediction of CPP candidates with the potential for transduction into cells, the mechanisms by which CPPs penetrate cells and various tissues have not yet been elucidated at the molecular interaction level. Recently, the skin-penetrating ability of CPPs has gained wide attention and emerged as a simple and effective strategy for the delivery of macromolecules into the skin. Studies on the skin structure have suggested that the penetration potential of CPPs is based on the molecular interactions and characteristics of the lipid lamellar structure between corneocytes in the stratum corneum. This review provides a brief overview of the general properties, transduction mechanisms, applications, and safety issues of CPPs, focusing on CPPs with transdermal properties, that are currently being used to develop therapeutics and cosmetics.

Study on Penetration Mechanism of Shaped-Charge Jet under Dynamic Conditions

Aiming at the dynamic penetration process of a shaped-charge jet, we proposed a mathematical model for the penetration of a jet under dynamical conditions based on the theory of virtual origin and the Bernoulli equation taking into account the jet and target intensities. The dynamic penetration process of the jet was divided according to the penetration channel of the jet into the static target. The dynamic penetration model of the jet based on the unperturbed section and perturbed section was established. The penetration depth variation in the shaped-charge jet vertically penetrating target plates with different moving speeds (150~400 m/s) was analyzed by finite element software. The dynamic penetration model shows that with the increase in the target moving speed, the disturbed time of the jet continuously advances, and the dynamic penetration depth continuously decreases; as the velocity of the target increases, the penetration length of the unperturbed jet decreases and then becomes stable, while the penetration length of the perturbed jet decreases. The results showed that the mathematical model is consistent with the finite element simulation, and that the mathematical model can effectively characterize the penetration depth of the unperturbed and disturbed jet portions, adequately explain the dynamic response behavior of the jet penetrating a moving target, and effectively predict the dynamic penetration depth of the jet under the influence of the target movement.

Chiral 4-O-acylterpineol as transdermal permeation enhancers: insights of the enhancement mechanisms of a transdermal enantioselective delivery system for flurbiprofen

In order to devise more effective penetration enhancers, 4-O-acylterpineol derivatives which were expected to be hydrolyzed into nontoxic metabolites by esterase in the living epidermis, were synthesized from 4-terpineol (4-TER) enantiomers and straight chain fatty acids. Their promoting activities on the SR-flurbiprofen and its enantiomers were tested across full-thickness rabbit skin, as well as to correlate under in vitro and in vivo conditions. The permeation studies indicated that both d-4-O-acylterpineol and l-4-O-acylterpineol had significant enhancing effects, interestingly, d-4-O-aclyterpineol had higher enhancing effects than l-4-O-aclyterpineol with the exception of d-4-methyl-1-(1-methylethyl)-3-cyclohexen-1-yl octadec-9-enoate (d-4-T-dC18). The mechanism of 4-O-acylterpineol facilitating the drug penetration across the skin was confirmed by Attenuated total reflection-Fourier transformed infrared spectroscopy (ATR-FTIR) and molecular simulation. The mechanism of penetration enhancers promoting drug release was explored by the in vitro release experiment. Finally, a relative safety skin irritation of enhancers was also investigated by in vivo histological evaluation. The present research suggested that d-4-O-aclyterpineol and l-4-O-aclyterpineol could significantly promote the penetration of SR-flurbiprofen and its enantiomers both in vitro and in vivo, with the superiorities of high flux and low dermal toxicity.

Application of Miniature FBG-MEMS Pressure Sensor in Penetration Process of Jacked Pile

In order to study the penetration mechanism of jacked piles in viscous soil foundation, the stress variation law of the pile–soil interface was obtained by installing silicon piezoresistive earth pressure and pore water pressure sensors, and fiber Bragg grating (FBG) sensors in a model pile body, and the penetration characteristics of jacked piles in homogeneous viscous soil were defined. The test results show that: Fiber Bragg grating and silicon piezoresistive sensing technology can better meet the requirements of testing the characteristics of jacked pile in viscous soil. The ratio of pile lateral resistance to pile end resistance varies when pile is jacked in homogeneous viscous soil. In the early stage of pile jacking, the ratio of pile lateral resistance is small, and in the later stage of pile jacking, the ratio of pile lateral resistance increases, but the ratio of pile end resistance is still higher than that of pile lateral resistance. The ratio of the effective stress to the total radial stress is high, and the variation law of the two is consistent with the depth. The total radial stress, pore water pressure, and effective radial stress all exhibit the degradation phenomenon, and the degradation degree decreases gradually with the increase in penetration depth at the same depth. The ratio of excess pore water pressure to overburden weight decreases with the increase in depth, and the maximum value is 87%. The research results can provide a reference for the engineering practice of jacked pile in viscous soil foundation.

Shape Effect of Nanoparticles on Tumor Penetration in Monolayers Versus Spheroids

The physical properties of nanoparticles (NPs), such as size, surface chemistry, elasticity, and shape, have exerted a profound influence on tumor penetration. However, the effect of shape on cellular uptake and tumor penetration is still unclear because of the different chemical compositions and shapes of tested particles and the use of inapposite cellular models. To discover the effect of NP shapes on cellular uptake and tumor penetration and bridge the gap between models in vivo and in vitro, elongated polystyrene (PS) NPs with a fixed volume, an identical chemical composition, and the same zeta potential, but with different aspect ratios (ARs), were generated. The physical properties, cellular uptake, tumor penetration, and corresponding mechanisms of these NPs were thoroughly investigated. We discovered that the elongated PS particles with higher ARs had lower uptake rates in the 2-dimensional cell monolayer culture model in vitro, but they showed optimal ARs in the evaluated three-dimensional spheroid model. Although the elongated PS particles had a similar tumor penetration mechanism (mainly through extracellular pathways), the percentage of penetration using these mechanisms was strongly dependent on the ARs. As an alternative model for studies in vivo, spheroids were used instead of the cell monolayer for the development of drug delivery systems. In addition, the physicochemical properties of NPs must be delicately balanced and adjusted to achieve the best therapeutic outcomes.

[Effects of Frankincense and Myrrh essential oil on transdermal absorption of ferulic acid in Chuanxiong]

The aim of this paper was to explore the effects of Frankincense and Myrrh essential oil on transdermal absorption, and investigate the mechanism of permeation on the microstructure and molecular structure of stratum corneum. Through the determination of stratum corneum/medium partition coefficient of ferulicacid in Chuanxiong influenced by Frankincense and Myrrh essential oil, the effects of volatile oil of frankincense and Myrrh on the the microscopic and molecular structure of stratum corneum were explored by observation of skin stratum corneum structure under scanning electron microscopy, and investigation of frankincense and myrrh essential oil effects on the molecular structure of keratin and lipids in stratum corneum under Fourier transform infrared spectroscopy. The results showed that the oil could enhance the distribution of ferulic acid in the stratum corneum and medium, and to a certain extent damaged the imbricate structure of stratum corneum which was originally regularly, neatly, and closely arranged; some epidermal scales turned upward, with local peeling phenomenon. In addition, frankincense and myrrh essential oil caused the relative displacement of CH2 stretching vibration peak of stratum corneum lipids and amide stretching vibration peak of stratum corneum keratin, indicating that frankincense and myrrh essential oil may change the conformation of lipid and keratin in the stratum corneum, increase the bilayer liquidity of the stratum corneum lipid, and change the orderly and compact structure to increase the skin permeability and reduce the effect of barrier function. It can be concluded that Frankincense and Myrrh essential oil can promote the permeation effect by increasing the distribution of drugs in the stratum corneum and changing the structure of the stratum corneum.

[Effects of Frankincense and Myrrh essential oil on transdermal absorption in vitro of Chuanxiong and penetration mechanism of skin blood flow]

The aim of this paper was to explore the effects of Frankincense and Myrrh essential oil on transdermal absorption in vitro of Chuanxiong, and to investigate the possible penetration mechanism of their essential oil from the perspective of skin blood perfusion changes. Transdermal tests were performed in vitro with excised mice skin by improved Franz diffusion cells. The cumulative penetration amounts of ferulic acid in Chuanxiong were determined by HPLC to investigate the effects of Frankincense and Myrrh essential oil on transdermal permeation properties of Chuanxiong. Simultaneously, the skin blood flows were determined by laser flow doppler. The results showed that the cumulative penetration amount of ferulic acid in Chuanxiong was (8.13±0.76) μg•cm⁻² in 24 h, and was (48.91±4.87), (57.80±2.86), (63.34±4.56), (54.17±4.40), (62.52±7.79) μg•cm⁻² respectively in Azone group, Frankincense essential oil group, Myrrh essential oil, frankincense and myrrh singly extracted essential oil mixture group, and frankincense and myrrh mixed extraction essential oil group. The enhancement ratios of each essential oil groups were 7.68, 8.26, 7.26, 8.28, which were slightly greater than 6.55 in Azone group. In addition, as compared with the conditions before treatment, there were significant differences and obvious increasing trend in blood flow of rats in Frankincense essential oil group, Myrrh essential oil group, frankincense and myrrh singly extracted essential oil mixture group, and frankincense and myrrh mixed extraction essential oil group when were dosed at 10, 20, 30, 10 min respectively, indicating that the skin blood flows were increased under the effects of Frankincense and Myrrh essential oil to a certain extent. Thus, Frankincense and Myrrh essential oil had certain effect on promoting permeability of Chuanxiong both before and after drug combination, and may promote the elimination of drugs from epidermis to dermal capillaries through increase of skin blood flow, thus enhancing the transdermal permeation amounts of drugs.

Monocyclic monoterpenes as penetration enhancers of ligustrazine hydrochloride for dermal delivery

The purpose of this study was to explore the enhancing effects and the mechanism of monocyclic monoterpene penetration enhancers (menthol and menthone) on the transdermal absorption of ligustrazine hydrochloride (LH). Franz-type diffusion cells were used to determine percutaneous parameters of LH in vitro and surface changes of porcine skin were studied by a scanning electron microscope (SEM). The effects of promoters on the biophysical natures of stratum corneum (SC) were researched by Fourier transform-infrared (FT-IR). Penetration parameters of menthol (p < 0.01) and menthone groups (p < 0.05) were greater than those of the control; morphological changes of skin monitored by SEM demonstrated that the menthone group had the most disruption and desquamation of SC flakes, which resulted from extracted lipids. FT-IR measurements showed menthone had the greatest changes in peak shift and peak area, which resulted from C-H stretching vibrations of SC lipids. The results suggest that the penetration mechanism might include disturbing and extracting SC lipids and the hydrogen bond connection.