Controlled Release With Emphasis on Ultrasound-Induced Release

Mesoporous silica nanoparticles (MSNs) represent a promising approach to be used as nanocarriers because they fulfill some basic criteria: biocompatibility, high loading capacity and possibility of easy surface modifications. As a consequence, MSNs have been employed to design sophisticated stimuli-responsive nanocarriers able to release the entrapped cargo on demand. Among those stimuli ultrasound (US) is considered as one of the most promising triggers for drug delivery systems due to the high tissue-penetrating capability and non-invasiveness. Recently, we employed US as a stimulus to control the drug release from MSNs for the first time, and found that acoustic cavitation played a key role in triggering the release. Those US-responsive MSNs were transported using cellular vehicles toward disease areas where they demonstrated their capacity to kill cancer cells when exposed to US. Light is also an excellent trigger because of the high biocompatibility and the capacity to focus to very small regions. However, its poor penetration in living tissues compromises its use in a clinical scenario. An alternative could be the use of near infrared (NIR) as trigger, as it would be described in this chapter. Other option could be the use of magnetic fields as stimulus because it can reach deep areas into the living tissue without damaging the surrounding tissues. MSNs have been combined with magnetic fields in a many different approaches and a quick overview is here provided. This chapter will show how some of these external stimuli represent a valuable tool for fighting complex diseases such as cancer.