Background: In conventional drug delivery, the drug concentration in the blood raises once the drug
taken, and then peaks and declines. Since each drug has a level above which it is toxic and another level below
which it is ineffective, the drug concentration in a patient at a particular time depends on compliance with the
Methods: To achieve more effective efficacy and fewer side effects of drugs, the drug carriers with desirable
dosing and controllable release property of drugs are highly desired. Stimuli-responsive capsules with smart gating
membranes or hydrogel-based membranes as capsule shells are ideal candidates. The smart capsule membranes
enable efficient encapsulation of drugs within the large inner volume, and the responsive gating membranes
or hydrogel-based membranes could control the release rate of encapsulated drugs in responding to environmental
stimuli. The trigger stimuli could be either artificial or natural ones corresponding to specific diseases,
such as temperature, pH, glucose concentration, specific ion, light, and magnetic field.
Results: This review highlights the recent development in stimuli-responsive capsule membranes for controlled
release in pharmaceutical applications, including two types of stimuli-responsive capsule membranes with different
architectures for on/off release and burst release, which can achieve potential uses of case-dependent on/off
release and burst release.
Conclusion: The preponderances of the smart capsule membranes are that the capsules are with controllable inner
space for drug vehicles with desired dose and stimuli-responsive membrane as shell to release drugs at a desired
site and/or moment. However, the actual difficulties for the stimuli-responsive capsule membrane systems to go
before they can be applied widely in the biomedical fields are discussed. The future works should focus on the
improvements of biocompatibility, biodegradability and stimuli-responsiveness of the capsule membranes, easy
and scalable fabrication techniques with further decrease of the capsule size for more efficient in vivo applications,
and the diversification of the multi-compartmental capsule architectures with multi-stimuli-responsive
characteristics for controlled release.