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INNOSC Theranostics and
Pharmacological Sciences The biochemical and biophysical guide for photodynamic therapy

reaction that leads to cellular destruction. HDP is activated Conversely, when PSs are transported by LDLs, early and
by light in the wavelength range of 763 nm. Chlorophyll, significant damage to cancer cells takes place, primarily
another porphyrin, plays a vital role in photosynthesis in through necrotic and apoptotic processes.
plants. It absorbs sunlight and converts it into chemical
energy, which is then used to synthesize organic 8. Side effects and contraindications in PDT
compounds. PDT has relatively few contraindications. These include
Chlorophyllins are chemical compounds derived hypersensitivity to the ingredients of topical preparations
from chlorophyll. More specifically, they are chlorophyll used in the treatment of dermatological conditions and
derivatives in which the magnesium ion is replaced by diseases associated with photosensitivity (e.g., lupus and
another metal, most commonly copper. These compounds porphyrias). Patients with porphyrias, a group of rare
are known for their characteristic green color, similar to metabolic diseases linked to impaired porphyrin synthesis,
chlorophyll, and have various medical and industrial may be at increased risk of photosensitization reactions. As
applications. The activation range for this PS is 690 nm. such, the use of PDT may be limited in these individuals.
Phthalocyanines are a group of organic dyes containing People with advanced kidney or liver disease may have a
a phthalocyanine ring, whose structure is similar to reduced ability to eliminate photosensitizing agents, which
that of chlorophyll. However, phthalocyanines contain could increase the risk of side effects. The safety of PDT
nitrogen atoms in a place where the magnesium is found in during pregnancy has not been fully investigated, and as a
chlorophyll. The most important and well-known member precaution, it is generally recommended to avoid PDT in
of this group is copper phthalocyanine. Phthalocyanines pregnant women, particularly during the first trimester. It
are activated by light in the range of 650 – 800 nm. is worth emphasizing that each case should be considered
individually, with decisions regarding the use of PDT made
Bacterioporphyrins are chemical compounds that, like by the attending physician, who must take into account the
other porphyrins, contain the characteristic porphyrin patient’s overall health and the specifics of their condition.
ring. They differ from typical porphyrins such that they are Regardless, side effects manifest as a modulation of the
found in bacteria, and their structure may vary from those inflammatory response and local immunosuppression,
present in eukaryotic organisms. The activation range for which may result in pain, burning, swelling, and redness
bacterioporphyrins is 600 – 700 nm. at the irradiation site. These symptoms typically resolve

7. Distribution of PSs to cancer cells within a few hours after the procedure, although swelling
and erythema may persist for several days. A late side effect
The mechanisms underlying the distribution of PSs used may include hyper- or hypo-pigmentation at the treatment
in PDT to cancer cells are not fully understood. However, site, particularly in patients with darker skin types. Skin
it is believed that their selective permeability through peeling is also a normal reaction to PDT. In addition, PDT
cancer tissue plays a key role in this process. As the may increase the expression of antigens on the surface of
hydrophobicity of a given chemical compound increases, cancer cells, which can enhance the immune response.
the affinity of the PS for cancer tissue also increases. This General reactions such as fatigue or headache have also
notion is supported by studies showing that PSs bound been reported in some patients.
to liposomes exhibit greater effectiveness and selectivity
in targeting cancer cells. The distribution of these It is important to note that PDT has shown promising
sensitizers is enhanced by the inclusion of amphiphilic results as a treatment for Barrett’s esophagus, though its
systems, which facilitate their delivery to the cancer cells. use may be limited due to certain undesirable effects.
These systems are stable in aqueous environments, yet With ongoing studies in modern laboratories and clinical
possess non-polar compartments that can accommodate facilities, efforts are underway to improve the efficacy of
substrates. One effective strategy involves combining PSs PDT while minimizing side effects. Furthermore, research
with low-density lipoproteins (LDLs), as various types of is exploring the potential impact of genetic abnormalities
cancer cells secrete a significant number of membrane on PDT effectiveness. By integrating the knowledge gained
receptors for LDLs. In cancer cells, PSs localize in the so far, PDT has the potential to become a breakthrough
plasma membrane, Golgi apparatus, rough endoplasmic treatment in medicine. 30
reticulum, and mitochondrial membrane. The mode of 9. New perspectives in PDT
PS transport into the cell determines the type of cellular
response in the target tissue. When PSs are transported The heavy atom effect and chemical configuration play
by albumin, extensive impairment of the vascular system crucial roles in enabling boron-dipyrromethene (BODIPY)
occurs, leading to tumor ischemia and hypoxia (Table 2). derivatives to generate O for PDT. BODIPY and its
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Volume 8 Issue 2 (2025) 25 doi: 10.36922/itps.4559