Biomedical Engineering Reference
In-Depth Information
from the location, the special distribution of different monomers or the
macromolecular topological structure of HBPs, plays a significant role in the
inherent attributes of the macromolecular architecture except for the selection
of monomers. Through selection of an appropriate synthetic method, the
functionality could be further controlled by means of adjusting the molecular
structure and topology. Particularly for HBPs, the functionalization hinges on
the fundamental parameters involving the molecular weight, polydispersity
(PDI), and degree of branching (DB). It has been well realized that an
appropriate combination of hydrophilic/hydrophobic balance in the polymer
chains is required for the occurrence of a phase transition. Based on this
concept, backbone-thermoresponsive hyperbranched polymers have been
synthesized:
7
PTP of butane-1,4-diol diglycidyl ether and various triols can
afford HBPs with a thermoresponsive backbone, and both drugs and genes can
be efficiently delivered.
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5.3 Functionality of Delivery
Currently, we have witnessed a rapidly increasing amount of publications
related to applications of HBPs and their assemblies in drug and gene delivery
because of their advantages of morphological varieties, excellent template
ability, facile functionalization, and smart responsiveness. These advantages
are paving the way for biomedical applications of HBPs and their self-
assemblies towards the direction of smart, programmable, and controlled
delivery. Modification of pharmaceutical nanocarriers is normally used to
control their biological properties in a desirable fashion and make them
simultaneously perform various diagnostic or therapeutic functions in the
delivery process. Therefore, functional materials are of great significance for
drug and gene delivery. The applications of HBPs and their self-assemblies in
this field are emerging just in the nick of time. Herein, we will classify the
following work on HBP nanocarriers into five parts based on the functionality
of delivery.
5.3.1 Responsiveness
The effect of drug therapy or gene transfection is closely related to the release
behavior of the delivery system in the body. The responsiveness is expected to
control the release behavior, making the delivery more efficient. Driven by a
need to control drug or gene release in response to an appropriate stimulus,
various stimuli-responsive HBPs and their assemblies have been developed as
smart vehicles and studied extensively, comprising temperature-, pH-, redox-,
light-, magnetic-, and enzyme-responsive ones, etc. The typical external stimuli
can be logically categorized into three groups: physical (light, electric,
magnetic, ultrasound, mechanical, and temperature), chemical (pH, ionic
strength, solvent, electrochemical, and specific substances), and biological
(enzymes
and
receptors).
Stimuli-responsive
HBPs
have
the
capacity
to
