Table 3.

External stimuli and corresponding mechanism of drug release from liposomes

External stimulus	Mechanism of release	Ref.
Ultrasound High intensity focused ultrasound (HIFU) or Low frequency Ultrasound	•Ultrasonic beam focused at a focal point •Heating of diseased area administered with drug encapsulated liposomes •Microcavitation (bursting of gas bubbles, disruption of membrane leading to drug release)	[ 152 , 161 , 162 ]
Magnetic field High Frequency Magnetic fields or Low frequency alternating current (AC) magnetic fields	•Requires thermally responsive liposomes •Hyperthermia due to heating above the gel‐to‐liquid transition temperature •Magneto‐mechanical actuation of bilayer •Low frequency magnetic fields are considered safer	[ 153 , 154 , 155 ]
Near Infrared Light	•Photosensitive agent loaded liposomes. •Heating of particles encapsulated in liposomes upon radiation (magnetic and gold nanoparticles) •Heating effects causes microcavity and bilayer disruption •Other mechanism is cell penetrating peptide activation upon NIR light exposure	[ 156 , 157 , 158 ]
Ultraviolet Light	•UV light sensitive agents grafted onto liposomes •Activation of photosensitive agent upon exposure •Polymerization reactions between photosensitive lipid molecules	[ 159 , 160 ]