ABSTRACT
Crosslinked proteins are widely used as the encapsulating membranes in microcapsules for many biomedical and food industries. The interfacial rheological properties of these capsules are due to the complex microstructure of cross-linked globular proteins owing to structural changes at quaternary, tertiary and secondary levels. These changes in structure can be induced by high protein concentration, hydrophobic-hydrophillic interfaces, and pH. In this work, the interfacial viscoelastic rheological properties of human serum albumin (HSA) microcapsules are estimated using a novel electrodeformation technique exhibiting creep and oscillatory responses. Insights into the microstructure-rheology relationship are obtained using FTIR and SEM studies. The results show a complex dependence of the interfacial properties on the size, concentration and pH of the capsules. An interplay of inter-molecular interactions, adsorption and multilayer formation, accessibility to reactive functional groups, and dependence on the relative content of alpha helix, beta sheet and beta turn is observed. The interfacial rheological properties are estimated using the Burger model and creep is found to sensitively affect the rheological properties due to irreversible changes in microstructure. Furthermore, the electrodeformation technique allows analysis of interfacial rheology at high frequencies, 10 Hz to 1 kHz, which is otherwise not easily possible with conventional rheometers.
Subject(s)
Serum Albumin, Human , Humans , Capsules , Adsorption , RheologyABSTRACT
It is known that the microstructure and thereby the mechanical properties of membranes constituting microcapsules are sensitive to parameters such as precursor concentration and pH. In the case of polysiloxane microcapsules, the oligomers, which are already formed in the continuous oil phase, because of the inherent moisture content in the oil phase, deposit on the membrane surface, resulting in the formation of a microstructure with a hairy layer. An electrodeformation investigation shows that the deposition of these oligomers is predominant in the smaller microcapsules compared to the larger ones and results in strain hardening and plasticity in the microcapsule membrane at high deformation. However, if the hydrolysis time during the synthesis of microcapsules is controlled, a smooth morphology (with a diminished hairy layer) can be realized for smaller capsules, as well. This work, using the electrodeformation method, demonstrates significant viscoelasticity and plasticity in the response of the capsules to applied electric stress and establishes an equivalence between simple spring and dashpot element-based phenomenological models with respect to the membrane properties using a linearized viscoelastic elasto-electrohydrodynamic model. The model can capture plasticity and strain hardening that are otherwise missed in simplified elasticity-based models.
ABSTRACT
The goals of lip reduction surgery are to reduce the volume of the lips and restore an aesthetic labial contour and to maintain an ideal volume relationship between upper and lower lips. The aim of this study was to minimize the excessive large lips by modifying the incision and to get more Indian appearance of the lips by using crab claw technique. A total of nine patients (six males and three females) of age-group 21-22 years, having aesthetic concern due to excessive large lips, were treated in the case series. The distance from the vermilion border to the lip line was recorded at midline and 6-7 mm apart from the either side, and the distance between two peaks corresponding to the philtral ridges at baseline and at 6 months follow-up. A mean reduction of approximately 10 ± 0.70 mm at midline, 10.11 ± 1.05 mm on the right side, and 9.55 ± 0.72 mm on the left side of the lip was obtained in all the nine cases. No postoperative complication was observed in any of the patients, and all the patients were satisfied with the result, which was carried out through a survey completed by all the patients. The lip reduction surgery using crab claw technique proved to be successful in achieving decreased lip volume while restoring anatomical morphometric pattern of lip to look more Indian way.
