Classification of stimuli–responsive polymers as anticancer drug delivery systems

Abstract

Although several anticancer drugs have been introduced as chemotherapeutic agents, the effective treatment of cancer remains a challenge. Major limitations in the application of anticancer drugs include their nonspecificity, wide biodistribution, short half-life, low concentration in tumor tissue and systemic toxicity. Drug delivery to the tumor site has become feasible in recent years, and recent advances in the development of new drug delivery systems for controlled drug release in tumor tissues with reduced side effects show great promise. In this field, the use of biodegradable polymers as drug carriers has attracted the most attention. However, drug release is still difficult to control even when a polymeric drug carrier is used. The design of pharmaceutical polymers that respond to external stimuli (known as stimuli-responsive polymers) such as temperature, pH, electric or magnetic field, enzymes, ultrasound waves, etc. appears to be a successful approach. In these systems, drug release is triggered by different stimuli. The purpose of this review is to summarize different types of polymeric drug carriers and stimuli, in addition to the combination use of stimuli in order to achieve a better controlled drug release, and it discusses their potential strengths and applications. A survey of the recent literature on various stimuli-responsive drug delivery systems is also provided and perspectives on possible future developments in controlled drug release at tumor site have been discussed.

Thermosensitive magnetic liposomes with doxorubicin cell-penetrating peptides conjugate for enhanced and targeted cancer therapy

“…This drawback limited the use of CPPs as drug delivery systems (Torchilin, 2007). With the focus of solving this dilemma, stimulus-responsive nanostructures have been introduced to build ''off-on'' switches to control CPPs' activity (Taghizadeh et al, 2015). During the first phase of carrier delivery, the nonspecific CPPs function is sterically shielded by nanocarrier.…”

Smart hydrogels for 3D bioprinting

“…The main advantage of electric field responsive hydrogels over other pH responsive gels is the control of swelling properties by modulating the electric field. Electric field responsive hydrogels can undergo swelling, shrinking, or bending depending on the stimuli factors [83][84][85][86][87][88] . For example, acid sodium salt-modified pluronic hydrogel experience bends in salt solution without contacting with anode or cathode when electric field applied [84] .…”

Ultrasound-responsive nanobubbles contained with peptide–camptothecin conjugates for targeted drug delivery

“…With the focus of solving this dilemma, stimulusresponsive nanostructures have been introduced to build ''off-on'' switches to control CPPs' activity (Taghizadeh et al, 2015), which were based on sensitivity to endogenous triggers (e.g. enzymatic activity and pH) and external triggers (e.g.…”