Recognition based separation of HIV-Tat protein using avidin–biotin interaction in modified microfiltration membranes

Reversibly Attached Phospholipid Bilayer-Functionalized Membrane Pores

We report the development of reversibly attached phospholipid bilayer (PLB)-functionalized membrane pores that enabled reusability of the membrane matrix as well as the phospholipid. The functionalized architecture was constructed based on electrostatic interactions, which facilitate the reversible attachment-detachment sequence of the functional moieties within membrane pores. To demonstrate potential application, an enzyme, glucose oxidase (GOx), was electrostatically immobilized within the PLB-functionalized membrane and enzymatic catalysis was conducted under the convective flow mode. The GOx-immobilized membrane demonstrated satisfactory activity and stability. Convective flow of the substrate solution resulted in significantly higher activity than diffusive flow. Then, the enzyme was detached keeping the functional PLB backbone intact. Detachment of the enzyme without affecting the functional activity of PLB backbone permits attachment of fresh enzyme. In addition, reusability of the phospholipids is also of great importance as they have wide range of applications, but their usage is limited by higher cost. We have demonstrated the detachment of the PLB from the membrane using a simple technique. Characterization of the detached phospholipid confirmed retention of the original structural and functional properties as exhibited before attachment. To the best of our knowledge, this is the first study on reversible PLB formation within membrane pores and demonstration of a detachment technique, while maintaining the structural and functional properties of the phospholipid.

An integrated experimental and modeling approach to propose biotinylated PLGA microparticles as versatile targeting vehicles for drug delivery

Polymeric microparticles with covalently attached biotin are proposed as versatile targeting vehicles for drug delivery. The proposed microparticles made of 85/15 poly (lactic-co-glycolic acid) (PLGA) will have biotin available on the outside of the particle for the further attachment with an avidin group. Taking advantage of biotin's high affinity for avidin, and avidin's well-known chemistry, the particle has the potential to be easily coated with a variety of targeting moieties. This paper focuses on the design and resulting effect of adding biotin to PLGA microparticles using an integrated experimental and modeling approach. A fluorescent-tagged avidin (488-streptavidin) was used to confirm the presence and bioavailability of biotin on the outside of the particles. For the purpose of this study, bovine serum albumin (BSA) was used as a model therapeutic drug. Microparticles were created using two different types of polyvinyl alcohol 88 and 98 mol% hydrolyzed, which were then analyzed for their size, morphology, and encapsulation capacity of BSA. Release studies performed in vitro confirmed the slow release of the BSA over a 28-day period. Based on these release profiles, a release kinetics model was used to further quantify the effect of biotinylation of PLGA microparticles on their release characteristics by quantitatively extracting the effective drug diffusivity and drug desorption rate from the release profiles. It was found that the biotinylation of the PLGA microparticles slowed down both the drug desorption and drug diffusion process, which confirmed that biotinylated PLGA microparticles can be used for controlled drug release. The presented technology, as well as the proposed integrated experimental and modeling approach, forms a solid foundation for future studies using a cell-specific ligand that can be attached to avidin and incorporated onto the microparticles for targeted delivery.

Functionalized Membranes by Layer-By-Layer Assembly of Polyelectrolytes and In Situ Polymerization of Acrylic Acid for Applications in Enzymatic Catalysis

This research work was directed toward the development of highly active, stable, and reusable functionalized polymeric membrane domains for enzymatic catalysis. Functionalized membranes were created by two different approaches. In the first approach, which involved alternative attachment of cationic and anionic polyelectrolytes, functionalization was performed using a layer-by-layer (LBL) assembly technique within a nylon-based microfiltration (MF) membrane. In the second approach, a hydrophobic polyvinylidene fluoride (PVDF) MF membrane was functionalized by the in situ polymerization of acrylic acid. The enzyme, glucose oxidase (GOX), was then electrostatically immobilized inside the functionalized membrane domains to study the catalytic oxidation of glucose to gluconic acid and H2O2. Characterization of the functionalized membranes, in terms of polyelectrolyte/polymer domains and permeate flux, was also conducted. The kinetics of H2O2 formation was discussed, along with the effects of residence time and pH on the activity of GOX. The stability and reusability of the electrostatically immobilized enzymatic system were also investigated.