Introduction

Protein-carbohydrate interactions play an important role in many biological processes including cell interactions with immune systems, tumor metastasis, adhesion of infectious agents to host cells and many more.1,2 Proteins involved in these signalling and processing pathways are known as lectins.3,4 These carbohydrate binding proteins are wide-spread in nature and they differ from antibodies or enzymes entities.5 For example, it has been shown that some viruses such as HIV express many carbohydrate entities at their surface. These glycosylated surfaces enable them to bind to specific lectins of the immune system cells. Therefore, one of the promising strategies for infectious diseases would be to design competing systems with higher lectin affinity than pathogens, thus preventing their adhesion. Although the binding between single carbohydrates and lectins is weak, it could be greatly enhanced by the multivalent effect of densely packed carbohydrate molecules with unique functionalities, which is also known as the “glycocluster effect”.6 Glyconanoparticles as carbohydrate-based systems provide in a similar manner to mimic the behavior of naturally existing glycocalyx. Therefore, the fabrication and engineering of innovative glyconanoparticles with unique physiochemical properties help to further enhance their specific recognition properties on multivalent scaffolds in glycoscience.

Recent and elegant synthetic routes have allowed polymer chemists to prepare a wide range of glyconanoparticles that provide strong and selective recognition properties towards lectins.7-11 In particular, amphiphilic block glycopolymers have attracted a great attention in terms of their ability to form various types of glyconanoparticles. These amphiphilic glycopolymers are generally composed of biocompatible, biodegradable hydrophobic polymer blocks covalently bonded to a biocompatible hydrophilic block.12-14 Some recent studies have shown that amphiphilic block glycopolymers with different carbohydrate compositions were used to produce nanoparticles, such as micelles, nanospheres, core-shell nanoparticles, micelle-like nanoparticles, crew cut micelles, nanocapsules and polymersomes.15-19 These studies facilitate the understanding and investigation of

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glycopolymer-lectin-binding activities that are significantly influenced by glycopolymer architecture, valency, size, and density of binding elements. Furthermore, they offer a promising route for the creation of a broad variety of bioactive self-assembled glyco-nanostructures for biomedical applications such as drug delivery, biomaterials, bio- and nano-technologies, and gene therapy.20-24 During the last few of years, a number of strategies devoted to prepare glycopolymers via single electron transfer living radical polymerization (SET-LRP) technique has exploded.

In this chapter, SET-LRP was used to synthesize several types of amphiphilic block co-glycopolymers bearing mannose moieties by using methyl acrylate (MA), glycomonomer (ManAc) and/or poly(ethylene glycol) (PEG) as hydrophobic and hydrophilic blocks, respectively. Mannose glycomonomer was prepared according to the procedure reported by Qiang et al.25 Poly(ethylene glycol) bis(2- bromoisobutyrate) (PEG-Br) was used as an initiator to prepare amphiphilic triblock glycocopolymer. The self-assembly of these well-defined amphiphilic glycopolymers was investigated in aqueous solution to obtain glyconanostructures with various size and morphologies. The resulting glyconanoparticles were further investigated for their binding affinities with lectins, in particular with DC-SIGN, which is a human C-type lectin present on both macrophages and also dendritic cell subpopulations. DC-SIGN binds to micro organisms and host molecules by recognizing surface rich in mannose containing glycans through multivalent glycan-protein interactions and notably serves a target molecule for several viruses such as human immunodeficiency virus (HIV) and hepatitis C virus (HCV).26,27

Various analytical methods have been developed to study multivalent carbohydrate-lectin interactions.8 Surface plasmon resonance (SPR) spectrometer that was used to analyze the interaction between DC-SIGN and the glyconanoparticles in this study monitors the interaction of two or more molecules or molecular assemblies in real time. This technique is very sensitive and can be used to detect association of glycoproteins or glycopolymers in even pico-molar concentrations. In the first part of this chapter, we reported the synthesis of well-

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defined amphiphilic glycopolymers via SET-LRP technique, their spontaneous self- assembly behavior and binding studies of the resulting nanoparticles with DC-SIGN. Polymeric micelles have a great potential for the contribution on the development of various drug delivery and release systems in pharmacological applications.28-32 Very recent and robust strategies have allowed polymer chemists to prepare polymeric micelles with different chemical functional groups and a broad variety of morphologies. In particular, the ability of glyco-micelles in terms of molecular recognition events and biological interaction processes could play a crucial role in order to develop cell specific targeted drug delivery systems. Therefore, they have attracted increasing attention due to their potential in biomimetic applications and human therapeutics.

Jiang and co-workers have performedthree types of self-assembled nanoparticles from triblock copolymers with the same polymeric backbone but different sugar regioisomers as pendant groups.33 Well-dispersed spheres were obtained from the polymer that is self-assembled into nanoparticles with the glyco block as the shell and the rod block as the core. The bioactivity of these nano-objects was analyzed with PNA and Erythrina cristagalli agglutinin (ECA) via quartz crystal microbalance (QCM). Similarly, Huang et al prepared glycosylated peptide-based block copolymers to form glycoparticles with well-defined morphologies in an aqueous solution.34

Hence, in the second part of this chapter, the synthesized amphiphilic glycopolymers were employed to prepare SB-216763 loaded glyco-micelles as nanocarriers. SB-216763, 3-(2,4-Dichlorophenyl)-4-(1-methyl-1H-indol-3-yl)-1H- pyrrole-2,5-dione, is a potent and selective inhibitor of the J and K isozymes of

glycogen synthase kinase-3 (GSK-3).35,36 GSK-3 is a serine/threonine protein kinase,

the activity of which is liked to some pathological conditions, such as diabetes

and/or insulin resistance, and Alzheimer's disease and also it is active in a number

of central intracellular signalling pathways.37 It has not been performed for the encapsulation and also the development of delivery and release systems so far. To the best of our knowledge, this is the first attempt to load SB-216763 into micelles

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successfully and also to investigate the in vitro release of SB-216763 from glyco- micelles with sufficient control. The results showed that SB-216763 loaded glyco- micelles can be utilized for the further investigations in cellular microenvironment due to a sustained drug release.