Recent Progress in Polymer Therapeutics as Nanomedicines

The term Polymer Therapeutics is defined as water-soluble biocompatible polymers that can function as bioactive nanomedicines, or as nanocarriers conjugated with therapeutic agents, i.e., low-molecular-weight drugs, proteins or nucleic acids. The therapeutic agent is loaded onto the polymeric nanocarrier either by conjugation or by supramolecular complexation. In 1975 Helmut Ringsdorf presented his idea regarding the use of polymers as targetable drug carriers. The high molecular weight therapeutic can only enter cells via endocytosis, resulting in longer circulation of the conjugate in the bloodstream compared to the free drug. In contrast, low-molecular-weight therapeutic agents pass rapidly through cell membranes and will non-selectively penetrate most tissues. The choice of polymeric backbone for the conjugate has great implications on the pharmacokinetics and pharmacodynamics of the drug. The polymer characteristics, such as molecular weight, polydispersity, architecture, charge and hydrophilicity, impose the drug solubility, its biodistribution, body excretion and the interaction with the immune system.