Polymeric hydrophilic polymers in targeted drug delivery - Artificial Cells, Cell Engineering and Therapy - page 42

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Polymeric hydrophilic polymers in targeted
drug delivery

K POON, V CASTELLINO and Y-L CHENG,
University of Toronto, Canada

2.1 Introduction

Rapid progress in therapeutic systems over the past two decades can be
attributed to both critical advances in molecular medicine and to the
development of new, versatile materials. Foremost among these, polymers
and hydrogels have been key components used in the packaging of small
molecule drugs, peptide and protein drugs, DNA, viruses and cells in targeted
drug delivery and in cell encapsulation applications. In this chapter, we present
an overview of the use of hydrophilic polymers in drug targeting, with the goal
of illustrating how hydrophilic polymers can be designed for targeting by
exploiting physiologic conditions or external stimuli. In Section 2.2, a brief
review of hydrophilic polymers is provided, with some detail on natural and
synthetic polymers that are prominently featured in targeting applications.
Temperature and pH-responsive polymers are also covered. In Section 2.3,
mechanisms of drug targeting aimed at sites ranging from macroscopic points
of administration to molecular and intracellular level targets are discussed,
together with corresponding material design strategies. Illustrative examples are
included with references to more thorough reviews.

2.2 Properties and classification of hydrophilic

polymers

Hydrophilic polymers have the potential to be biocompatible, and have therefore
attracted extensive attention in biomedical and drug delivery applications. 1±5
They can be tailor-designed at both the molecular level and the device level. At
the molecular level, they can be synthesized as homopolymers of a single
hydrophilic monomer, or as random or block copolymers of a hydrophilic
monomer with either hydrophilic or hydrophobic monomers. They can also be
grafted onto the backbone of other polymers, or made into branched structures
with varying degrees of branching. At the device level, hydrophilic polymers