Ph.D Thesis

Ph.D StudentShamai Keren
SubjectHeterogeneous Polymer Brushes and Their Interactions with
DepartmentDepartment of Biotechnology
Supervisor PROF. Havazelet Bianco-Peled
Full Thesis textFull thesis text - English Version


The research described in this thesis deals with heterogeneous polymer brushes and their interactions with proteins. The term “polymer brush” refers to an assembly of polymer chains, which are attached by one end to an interface. One of the most interesting applications of polymer brushes is utilizing them as a means to manipulate the protein-binding properties of a surface.

In the current research we examined whether it is possible to manipulate the protein binding properties of a surface using a "heterogeneous polymer brush” (HPB), constructed from a mixture of a neutral repulsive polymer and a charged polymer. HPB in particular, can potentially be customized to prevent nonspecific adsorption of some proteins while enhancing the adsorption of others, a property that could be used in drug delivery systems, bio-separation, biosensors etc. To date, very few studies are available on two-component polymer brushes, and studies on the interactions between proteins and HPB are very rare.

The main goals of this research were first, to construct different architectures of HPB. Second, to study the structure of the HPB and third, to characterize the adsorption of proteins on these HPB. HPB having three different architectures were constructed and characterized: 1) diblock copolymer micelles with heterogeneous corona, formed via self-assembly of a binary mixture of diblock copolymers having the same hydrophobic block but a different hydrophilic block, 2) HPB on a flat surface formed from a binary mixture of diblock copolymers spread at air/water interface in a Langmuir trough, 3) HPB made of star terpolymers with heterogeneity along the radius, composed of linear ABC triblock terpolymers that are interconnected at one end.

The HPB were characterized using light scattering, small angle x-ray and neutron scattering, neutron reflectivity, High Performance Size Exclusion Chromatography and Langmuir trough - surface pressure isotherms. The tendency for protein binding was investigated using the different scattering techniques and Isothermal Titration Calorimetry.

Our results have shown that HPB can be successfully constructed. From the proteins binding assays, it was concluded that the ability of a HPB to absorb proteins differs from the protein adsorption ability of the pure components. Also, we have shown that the use of binary brush with a certain composition may enhance the adsorption of one protein and reduce the adsorption of another. The ability of the brush to adsorb proteins was related not only to its "in plane" heterogeneity, but also to the radial heterogeneity of the brush.