AFM surface morphology and friction force studies of microscale domain structures of binary phospholipids

Recent advances in superlubricity of liposomes for biomedical applications

Achieving superlubricity, a state of lubrication where friction nearly vanishes, has become one of the most promising approaches to combat friction-induced energy dissipation and medical device failure. Phospholipids are amphiphilic molecules comprising highly hydrophilic phosphatidylcholine head groups as well as hydrophobic hydrocarbon chains, When solubilized, phospholipids can readily self-assemble to form different structures such as bilayers and vesicles (liposomes). Recently, liposomes have been identified as excellent lubricants, especially in the boundary lubrication regime the most common lubrication status in the field of biotribology. In this review, we summarize recent progress in employing liposomes as key players for employing superlubricity in biomedical applications. The relationship between lipids and liposomes, manufacturing approaches, lubrication regimes, and regulation mechanisms of liposomes are discussed. Finally, we indicate possible future directions for the use of liposome-mediated superlubricity in biomedical applications.

Friction Determination by Atomic Force Microscopy in Field of Biochemical Science

Atomic force microscopy (AFM) is an analytical nanotechnology in friction determination between microscale and nanoscale surfaces. AFM has advantages in mechanical measurement, including high sensitivity, resolution, accuracy, and simplicity of operation. This paper will introduce the principles of mechanical measurement by using AFM and reviewing the progress of AFM methods in determining frictions in the field of biochemical science over the past decade. While three friction measurement assays-friction morphology, friction curve and friction process in experimental cases-are mainly introduced, important advances of technology, facilitating future development of AFM are also discussed. In addition to the principles and advances, the authors also give an overview of the shortcomings and restrictions of current AFM methods, and propose potential directions of AFM techniques by combining it with other well-established characterization techniques. AFM methods are expected to see an increase in development and attract wide attention in scientific research.

Properties of amphiphilic oligonucleotide films at the air/water interface and after film transfer

The self-assembly of amphiphilic hybrid materials containing an oligonucleotide sequence at the air/water interface was investigated by means of pressure-molecular area (Π-A) isotherms. In addition, films were transferred onto solid substrates and imaged using scanning force microscopy. We used oligonucleotide molecules with lipid tails, which consisted of a single stranded oligonucleotide 11 mer containing two hydrophobically modified 5-(dodec-1-ynyl)uracil nucleobases (dU11) at the 5'-end of the oligonucleotide sequence. The air/water interface was used as confinement for the self-assembling process of dU11. Scanning force microscopy of films transferred via Langmuir-Blodgett technique revealed mono-, bi- (Π ≥ 2 mN/m) and multilayer formation (Π ≥ 30 mN/m). The first layer was 1.6 ± 0.1 nm thick. It was oriented with the hydrophilic oligonucleotide moiety facing the hydrophilic substrate while the hydrophobic alkyl chains faced air. In the second layer the oligonucleotide moiety was found to face the air. The second layer was found to cover up to 95% of the sample area. Our measurements indicated that the rearrangement of the molecules into bi- and multiple bilayers happened already at the air/water interface. Similar results were obtained with a second type of oligonucleotide amphiphile, an oligonucleotide block copolymer, which was composed of an oligonucleotide 11 mer covalently attached at the terminus to polypropyleneoxide (PPO).

Development and in vitro evaluation of deacety mycoepoxydiene nanosuspension

Deacety mycoepoxydiene (DM), extracted from Phomopsis sp. A123 of thalassiomycetes, is a novel and potent anti-cancer agent. Due to its physicochemical characteristics, the drug, a poorly water-soluble weak acid, shows poor solubility and dissolution characteristics. To improve the solubility and dissolution, formulation of DM as nanosuspension has been performed in this study. Nanosuspensions were developed by high-pressure homogenization (HPH) (DissoCubes(®) Technology) and transformed into dry powder by freeze-drying. The nanosuspension produced was then investigated using optical microscope, photon correlation spectroscopy (PCS), zeta potential measurement, SEM, TEM, AFM, DSC and XRD. To verify the theoretical hypothesis on the benefit of increased surface area, in vitro saturation solubility and dissolution profile were investigated. In addition, the in vitro cell cytotoxicity was examined. Results showed that a narrow size distributed nanosuspension composed of unchanged crystalline state with a mean particle size of 515±18 nm, a polydispersity index of 0.12±0.03 and a zeta potential of -23.1±3.5 mV was obtained. In the in vitro dissolution test an accelerated dissolution velocity and increased saturation solubility could be shown for the MD nanosuspension. The in vitro cytotoxicity experiments provided evidence for an enhanced efficacy of the DM nanosuspension formulation compared to free DM solution. Taken together, these results illustrate the opportunity to formulate DM in nanosuspension form as an anti-prostate cancer delivery system.