Polyelectrolyte nanocomplex formation of heparin-photosensitizer conjugate with polymeric scavenger for photodynamic therapy

Nanomedicine in Clinical Photodynamic Therapy for the Treatment of Brain Tumors

The current treatment for malignant brain tumors includes surgical resection, radiotherapy, and chemotherapy. Nevertheless, the survival rate for patients with glioblastoma multiforme (GBM) with a high grade of malignancy is less than one year. From a clinical point of view, effective treatment of GBM is limited by several challenges. First, the anatomical complexity of the brain influences the extent of resection because a fine balance must be struck between maximal removal of malignant tissue and minimal surgical risk. Second, the central nervous system has a distinct microenvironment that is protected by the blood–brain barrier, restricting systemically delivered drugs from accessing the brain. Additionally, GBM is characterized by high intra-tumor and inter-tumor heterogeneity at cellular and histological levels. This peculiarity of GBM-constituent tissues induces different responses to therapeutic agents, leading to failure of targeted therapies. Unlike surgical resection and radiotherapy, photodynamic therapy (PDT) can treat micro-invasive areas while protecting sensitive brain regions. PDT involves photoactivation of photosensitizers (PSs) that are selectively incorporated into tumor cells. Photo-irradiation activates the PS by transfer of energy, resulting in production of reactive oxygen species to induce cell death. Clinical outcomes of PDT-treated GBM can be advanced in terms of nanomedicine. This review discusses clinical PDT applications of nanomedicine for the treatment of GBM.

Rational design of block copolymer self-assemblies in photodynamic therapy

Photodynamic therapy is a technique already used in ophthalmology or oncology. It is based on the local production of reactive oxygen species through an energy transfer from an excited photosensitizer to oxygen present in the biological tissue. This review first presents an update, mainly covering the last five years, regarding the block copolymers used as nanovectors for the delivery of the photosensitizer. In particular, we describe the chemical nature and structure of the block copolymers showing a very large range of existing systems, spanning from natural polymers such as proteins or polysaccharides to synthetic ones such as polyesters or polyacrylates. A second part focuses on important parameters for their design and the improvement of their efficiency. Finally, particular attention has been paid to the question of nanocarrier internalization and interaction with membranes (both biomimetic and cellular), and the importance of intracellular targeting has been addressed.

Additive effect of heparin on the photoinactivation of Escherichia coli using tricationic P-porphyrins

Polycationic porphyrins have received substantial attention in developing singlet oxygen-sensitizers for biological use such as in the photoinactivation of bacteria and photodynamic therapy (PDT) of tumor cells because they have strong binding affinities for DNA and proteins. However, these strong cellular interactions can retard elimination of the drug after PDT. Therefore, the studies on the interactions of porphyrins with other molecules present much interest, in order to modulate the sensitizers' activity or even remove them from the human body after PDT. Here, we studied the additive effect of heparin on the photoinactivation by polycationic porphyrins using Escherichia coli as a model cell. Tricationic P-porphyrin sensitizers substituted with an N-alkylpyridinium group (alkyl = pentyl (1a), hexyl (1b), and heptyl (1c)) or N-hexylammonium (1d) as the axial ligand were used. Additionally, dicationic Sb-porphyrin substituted with an N-hexylpyridinium group (1e) was prepared. We studied the additive effect of heparin on the photoinactivation of E. coli by 1a-1e. The bactericidal activities were evaluated using the half-life (T_1/2 in min) of E. coli and the minimum effective concentrations ([P]) of the porphyrin sensitizers. In the absence of heparin, the [P] values were determined to be 0.4-0.5 μM for 1a-1c and 2.0 μM for 1d-1e. The bactericidal activity of 1a-1c was completely retarded by the addition of heparin (1.0 μM). However, the addition of heparin (1.0 μM) could not completely retard the bactericidal activity of 1d-1e whose [P] values were relatively large. It is suggested that tricationic 1a-1c adsorbed onto the anionic heparin through electrostatic interactions. The adsorption of 1 on heparin disturbs the uptake of 1 into E. coli cells. Thus, the addition of heparin was found to be a useful method for retarding photoinactivation.

Synthesis of amide derivatives of chlorin e6 and investigation of their biological activity

In this work there is a synthesis of new photosensitizers which is based on amide derivatives of chlorin е6 . For the disclosure of an extra ring of the initial compound - pheophorbide a 1, we used primary aliphatic amines with 4-12 carbon atoms in the alkyl chain. The reaction is carried out under mild conditions in chloroform with heating to 40 ºС. The structure of all compounds obtained was confirmed by means of electronic, IR, 1Н-NMR spectroscopy and mass-spectrometry. The photoactivity and the dark toxicity of the compounds 2b-2h were investigated on two cancer cell lines: P-388 and K-562. The biological investigations revealed a good photoactivity and low dark toxicity of all compounds 2b-2f. The amide derivatives of chlorin е6 with 6 and 7 carbon atoms in the alkyl part showed the best results in our research. Thus, in this paper we propose a reliable scheme of synthesis of chlorin's photosensitizers which are promising agents for PDT.