Preparation of targeting proteoliposome by postinsertion of a linker molecule conjugated with recombinant human epidermal growth factor.

To develop a sterically stable, targeting proteoliposome, a postinsertion method was employed to biofunctionalize the liposome surface with a biocompatible anchor molecule (BAM) linker conjugated with epidermal growth factor (EGF) as a homing molecule. In this method, EGF was first conjugated with BAM that consisted of a hydrophilic reactive group at one end and oleic acid chains at the other end. The EGF-BAM complex was then inserted into the liposomal phospholipid bilayer through lipophilic interaction. When compared with the traditional surface modification method by amine coupling, the modification efficiency with BAM at 25 degrees C was about 2.5-fold higher, and the 24 h stability of the inserted BAM at 25 degrees C was also about 2.5-fold higher. The insertion affinity and stability of the BAM to the liposomal bilayer was not influenced by an increase in cholesterol concentration, a component in liposome preparation. Confocal microscopy studies showed that the proteoliposomes biofunctionalized with the BAM-EGF complex encapsulating Cy5 fluorescent dye were selectively bound to the surface of MDA-MB-231 cells overexpressing EGFR (epidermal growth factor receptor), but not to MCF-7 cells, which did not express EGFR. The same proteolipome encapsulating doxorubicin was selectively targeted to MDA-MB-231 cells and killed them. In sum, BAM could be used as a suitable postinsertion linker for biofunctionalization of liposome surface with high modification efficiency and stability. Furthermore, the protein used as a homing molecule maintained its bioactivity after the biofunctionalization.

Fabrication of protein-anchoring surface by modification of SiO2 with liposomal bilayer.

SiO(2) surface was successfully modified with phospholipid bilayer for biocompatibility by covering the planar surface with vesicular liposomes. By applying heat to rupture the vesicle, they were converted into a planar form. To effectively decorate the bilayer with biological molecules such as a protein, BAM (biological anchor for membrane) was used as a linker. It is a linear assembly consisting of oleyl chain, polyethylene glycol, and NHS (N-hydroxysuccinimide). After a target protein (BSA) was conjugated with BAM by NHS replacement, the conjugate was effectively inserted to the phospholipid bilayer through the lipophilic interaction between the oleyl chain and the lipid bilayer. The entire process was monitored and quantitatively analyzed by QCM (quartz crystal microbalance). BSA-BAM conjugate showed approximately 12-fold higher binding efficiency to the lipid bilayer than BSA alone. From this result, we conclude that SiO(2) surface could be modified to a lipid bilayer surface so as to anchor a protein by the action of BAM.

Two human cases of tick bite caused by Ixodes nipponensis.

We report two human cases of tick bite. A 63-year-old male had a pruritic pea-sized brownish nodule on the left popliteal area. Another 41-year-old male had an asymptomatic bean-sized black nodule in the pubic area. The ticks were identified as Ixodes nipponensis, which are the 18th and the 19th cases in Korea.