Light-Induced Liposomal Drug Delivery with an Amphiphilic Porphyrin and Its Chlorin and Bacteriochlorin Analogues

The development of targeted drug delivery
mechanisms in the human body is a matter of growing interest
in medical science. The selective release of therapeutic agents at a
specific target site can increase the therapeutical efficiency and at
the same time reduce the side effects. Light-sensitive liposomes can
release a drug by an externally controlled light trigger. Liposomes
containing photosensitizers that can be activated in the longer
wavelength range (650−800 nm) are particularly intriguing for
medical purposes. This is because light penetration into a tissue is
more efficient within this wavelength range, increasing their
potential applications. For this study, liposomes with an
encapsulated amphiphilic photosensitizer, the porphyrin 5,10-
DiOH (5,10-di(4-hydroxyphenyl)-15,20-diphenyl-21,23H-porphyrin), its chlorin (5,10-DiOH-chlorin) and its bacteriochlorin (5,10-DiOH-bacteriochlorin) were synthesized. The porphyrin
5,10-DiOH showed previously effective cargo release after liposomal encapsulation when irradiated at a wavelength of 420 nm. The
new synthesized chlorin and bacteriochlorin photosensitizers show additional absorption bands in the longer wavelength range,
which would enable excitation in deeper layers of tissue. Effective cargo release with chlorin at a longer wavelength of 650 nm and
bacteriochlorin at 740 nm was possible. Irradiation of chlorin allowed more than 75% of the cargo to be released and more than 60%
for bacteriochlorin. The new liposomes would enable selective drug release in deeper tissue layers and expand the range of possible
applications