In vitro and in vivo confocal Raman study of human skin hydration: assessment of a new moisturizing agent, pMPC.

The hydration capacities of a biomimetic polymer, 2-methacryloyloxethylphosphorylcholine polymer (pMPC), alone and microencapsulated, in association with another well known hydrating polymer, Hyaluronic acid, were investigated in vitro on skin models and in vivo on volunteers by using confocal Raman microspectroscopy. The hydration impact and the relative water content in the Stratum corneum were calculated from the Raman spectra using the OH (water)/CH3 (protein) ratio. Moreover, the follow-up of the presence of pMPC through the Stratum corneum was possible with confocal Raman microspectroscopy, using a characteristic vibration of pMPC, different from that of the encapsulating material. From our in vitro measurements, the improved hydration of the Stratum corneum was confirmed by the use of the encapsulated form of pMPC, which was higher when combined with Hyaluronic acid. On the basis of these in vitro findings, we validated this trend in in vivo measurements on 26 volunteers, and found a good correlation with the in vitro results. Mechanical and ultrastructural studies have been carried out to demonstrate the positive effects of the pMPC on the Stratum corneum function, namely the interaction with lamellar lipids and the plasticizing effects, which are both supposed to spell out the moisturizing effect. This study demonstrates the efficiency of a original hydrating agent, pMPC, entrapped with Hyaluronic acid in a new type of microcapsules by the use of a novel tool developed for both in vitro and in vivo approaches. This indicates a new step to evaluate and improve new moisturizers in response to the cosmetics or dermatologic demands.

An in vivo randomized study of human skin moisturization by a new confocal Raman fiber-optic microprobe: assessment of a glycerol-based hydration cream.

BACKGROUND: In a recent study, we demonstrated the ability of the new confocal Raman microprobe to investigate molecular and structural human skin composition under in vivo conditions. Experiments were performed at different anatomical sites, different layers, and with intervolunteer comparison. We also carried out feasibility tests using this probe to determine depth profiles of water content within the skin. OBJECTIVE: In the present investigation we employed this confocal Raman optical microprobe to rigorously objectify the resulting hydration capacities after application of a moisturizing enhancer. METHOD: The in vivo experiments were performed on 26 healthy volunteers and measurements were undertaken on six areas of the volar forearm after a randomized application of hydrating agents. Responses were evaluated by calculating the water/protein band ratio, which determines the water content in the skin. RESULTS: Data collected with the Raman microprobe showed significant changes between baseline values of control and treated skins. Statistical analysis performed on these data revealed an increase in skin moisture after application of a glycerol-based cream, which is the most widely used hydrating agent. CONCLUSION: Our results demonstrate clearly the potentials of this confocal Raman microprobe in the screening of hydrating agents or molecules under in vivo conditions. In the cosmetics field, this promising and suitable technique will undoubtedly offer new opportunities of hydration skin test evaluation.

In vivo chemical investigation of human skin using a confocal Raman fiber optic microprobe.

To evaluate the potential of a new in vivo confocal Raman microprobe, we undertake a pilot study in human skin. A fiber optic probe is operated with a 633-nm laser and trials are conducted in healthy volunteers. We examine changes in molecular composition and structure of the stratum corneum, from different volunteers, from different anatomical sites and skin layers. Main spectral variations are detected in the following regions: 800 to 900 cm(-1) (amino acids); 1200 to 1290 cm(-1) (proteins); and 1030 to 1130 cm(-1), 1300 to 1450 cm(-1), and 2800 to 2900 cm(-1) (lipids). Curve fitting of the amide 1 region performs in detail protein secondary structural variations of the amide 1 band. Protein conformation is also found to vary depending on the anatomical site and volunteer. Similar analysis of the 730- to 1170-cm(-1) spectral window reveals a different organization of lamellar lipids: gel for forearm and palm, and liquid-crystalline phase for fingertips. All these variations result from changes in the stratum corneum components such as natural moisturizing factor (NMF), lipids (namely ceramides), and water. Hierarchical clustering classification is also performed to sort out Raman data obtained from different subjects. Further improvement of the confocal probe would be to adapt a 360-deg configuration enabling access to other anatomical sites.

Shear force near-field optical microscope based on Q-controlled bimorph sensor for biological imaging in liquid.

Shear force near-field microscopy on biological samples in their physiological environment loses considerable sensitivity and resolution as a result of liquid viscous damping. Using a bimorph-based cantilever sensor incorporating force feedback, as recently developed by us, gives an alternative force detection scheme for biological imaging in liquid. The dynamics and sensitivity of this sensor were theoretically and experimentally discussed. Driving the bimorph cantilever close to its resonance frequency with appropriate force feedback allows us to obtain a quality factor (Q-factor) of up to 10(3) in water, without changing its intrinsic resonance frequency and spring constant. Thus, the force detection sensitivity is improved. Shear force imaging on mouse brain sections and human skin tissues in liquid with an enhanced Q-factor of 410 have shown a high sensitivity and stability. A resolution of about 50 nm has been obtained. The experimental results suggest that the system is reliable and particularly suitable for biological cell imaging in a liquid environment.