Characterization of chlorophyll derivatives in micelles of polymeric surfactants aiming photodynamic applications

Preparation and evaluation of oral self-microemulsifying drug delivery system of Chlorophyll

OBJECTIVE

This study was aimed at improving the water solubility and oral bioavailability of Chl by self-microemulsifying drug delivery system (Chl-SMEDDS).

METHODS

Compatibility experiments, pseudo-ternary phase diagram and central composite design were used to optimize the formulation. The selected systems were further evaluated for physical characteristics, including particle size, zeta potential, and appearance. The stability, in vitro dispersion test, and in vivo intestinal perfusion experiments were used to evaluate the SMEDDS.

RESULTS

The optimal composition of Chl-SMEDDS included: Labrafil M 1944 CS (35%), kolliphor RH 40 (46%), Transcutol HP (19%) and 60 mg/g Chl. The appearance of water emulsified Chl-SMEDDS was green and transparent. The particle size, ζ-potential, and transmission electron microscopy studies showed that spherical globules of Chl-SMEDDS with a size of about 22.82 ± 1.29 nm and a negative surface charge of -24.21 ± 3.45 mV were obtained. Chl-SMEDDS could remain stable at 25 °C and 4 °C for at least 6 months. The dispersion test showed that Chl-SMEDDS dispersed spontaneously to form microemulsion after disintegration of capsule shell and 90% drug dispersed in just 30 min in pH 1.2 HCl without any drug precipitation during the test period. In vivo intestinal perfusion experiment revealed that the main absorption site for Chl-SMEDDS was duodenum.

CONCLUSIONS

This study indicates that SMEDDS formulation could be an effective strategy for the oral administration of Chl.

Nanoscale integration of porphyrin in GroEL protein cage: Photophysical and photochemical investigation

In this paper, we introduce a new type of functional, supramolecular porphyrin conjugate created using the bacterial GroEL protein cage based on non-specific hydrophobic interaction. The synthesis, structure and property of the porphyrin conjugate were characterized by dynamic light scattering, UV-vis spectroscopy and fluorescence spectroscopy. We observed that the model zinc-tetraphenylporphyrin (Zn-TPP) with high hydrophobicity can be well-dispersed in aqueous solutions with the aid of GroEL open chamber, which is known to be a favorable nanocompartment for aggregation-prone molecules. The maximal encapsulation efficiency of Zn-TPP in GroEL was determined to be ~98%. It is further seen that the constructed double Zn-TPP-GroEL complex exhibited good photocatalytic activity in the model reactions of the production of singlet oxygen and the reduction of methyl viologen under illumination with visible light. Moreover, we found that GroEL can significantly improve the photostability of Zn-TPP molecules as a result of nanoscale assembly within its hydrophobic chamber. Hence enhanced water solubility and photostability of Zn-TPP, which are considered as the first two hurdles for the wide usage of porphyrins, were achieved simultaneously by the development of GroEL cage as a building block. Supramolecular nanostructures formed from porphyrins (or related molecules) and GroEL for photocatalysis would greatly simplify applications of such structures.

Exploiting Lipid and Polymer Nanocarriers to Improve the Anticancer Sonodynamic Activity of Chlorophyll

Sonodynamic therapy is an emerging approach that uses low-intensity ultrasound to activate a sonosensitizer agent triggering its cytotoxicity for selective cancer cell killing. Several molecules have been proposed as sonosensitizer agents, but most of these, as chlorophyll, are strongly hydrophobic with a low selectivity towards cancer tissues. Nanocarriers can help to deliver more efficiently the sonosensitizer agents in the target tumor site, increasing at the same time their sonodynamic effect, since nanosystems act as cavitation nuclei. Herein, we propose the incorporation of unmodified plant-extracted chlorophyll into nanocarriers with different composition and structure (i.e., liposomes, solid lipid nanoparticles and poly(lactic-co-glycolic acid) nanoparticles) to obtain aqueous formulations of this natural pigment. The nanocarriers have been deeply characterized and then incubated with human prostatic cancer cells (PC-3) and spheroids (DU-145) to assess the influence of the different formulations on the chlorophyll sonodynamic effect. The highest sonodynamic cytotoxicity was obtained with chlorophyll loaded into poly(lactic-co-glycolic acid) nanoparticles, showing promising results for future clinical investigations on sonodynamic therapy.

Photodamage on Staphylococcus aureus by natural extract from Tetragonia tetragonoides (Pall.) Kuntze: Clean method of extraction, characterization and photophysical studies

Photodynamic therapy (PDT) is a clinical modality that allows the destruction of tumor cells and microorganisms by reactive oxygen species, formed by the combination of photosensitizer (PS), molecular oxygen and adequate wavelength light. This research, through a clean methodology that involves pressurized liquids extraction (PLE), obtained a highly antimicrobial extract of Tetragonia tetragonoides, which rich in chlorophylls as photosensitizers. The Chlorophylls-based extract (Cbe-PLE) presented pharmacological safety, through the maintenance of cellular viability. In addition, Cbe-PLE showed great efficacy against Staphylococcus aureus, with severe dose-dependent damage to the cell wall of the pathogen. The obtained product has a high potential for the development of photostimulated phytotherapic formulations for clinical applications in localized infections, as a complementary therapeutic alternative to antibiotics.

Design of a nanostructured mucoadhesive system containing curcumin for buccal application: from physicochemical to biological aspects

Mucoadhesive nanostructured systems comprising poloxamer 407 and Carbopol 974P® have already demonstrated good mucoadhesion, as well as improved mechanical and rheological properties. Curcumin displays excellent biological activity, mainly in oral squamous cancer; however, its physicochemical characteristics hinder its application. Therefore, the aim of this study was to develop nanostructured formulations containing curcumin for oral cancer therapy. The photophysical interactions between curcumin and the formulations were elucidated by incorporation kinetics and location studies. They revealed that the drug was quickly incorporated and located in the hydrophobic portion of nanometer-sized polymeric micelles. Moreover, the systems displayed plastic behavior with rheopexy characteristics at 37 °C, viscoelastic properties and a gelation temperature of 36 °C, which ensures increased retention after application in the oral cavity. The mucoadhesion results confirmed the previous findings with the nanostructured systems showing a residence time of 20 min in porcine oral mucosa under flow system conditions. Curcumin was released after 8 h and could permeate through the porcine oral mucosa. Cytotoxicity testing revealed that the formulations were selective to cancer cells over healthy cells. Therefore, these systems could improve the physicochemical characteristics of curcumin by providing improved release and permeation, while selectivity targeting cancer cells.

Liposome and polymeric micelle-based delivery systems for chlorophylls: Photodamage effects on Staphylococcus aureus

Chlorophyll derivatives (Chls), loaded in F-127 polymeric micelles and DPPC liposomes as drug delivery systems (DDS), have been shown to be remarkable photosensitizers for photodynamic inactivation (PDI). Assays of photoinactivation of Staphylococcus aureus bacteria (as biological models) showed that the effectiveness of Chls in these nanocarriers is dependent on photobleaching processes, photosensitizer locations in DDS, singlet oxygen quantum yields, and Chl uptake to bacteria. These are factors related to changes in Chl structure, such as the presence of metals, charge, and the phytyl chain. The photodynamic activity was significantly greater for Chls without the phytyl chain, i.e., phorbides derivatives. Furthermore, the inactivation of S. aureus was increased by the use of liposomes compared to micelles. Therefore, this research details and shows the high significance of the Chl structure and delivery system to enhance the photodynamic activity. It also highlights the chlorophylls (particularly phorbides) in liposomes as promising photosensitizers for PDI.

A chloroplast-inspired nanoplatform for targeting cancer and synergistic photodynamic/photothermal therapy

A bioinspired nanoplatform composed of Cu(ii)-chlorophyll–hyaluronic acid nanoparticles (Cu(ii)Chl–HA NPs) was developed for targeting cancer and combined photodynamic/photothermal therapy.

Biomedical Platform Development of a Chlorophyll-Based Extract for Topic Photodynamic Therapy: Mechanical and Spectroscopic Properties

Photodynamic therapy (PDT) is a therapeutic modality that has shown effectiveness in the inactivation of cancer cell lines and microorganisms. Treatment consists of activating the photosensitizer (PS) upon light irradiation of adequate wavelength. After reaching the excited state, the PS can handle the intersystem conversion through energy transfer to the molecular oxygen, generating reactive oxygen species. This especially applies to singlet oxygen (¹O₂), which is responsible for the selective destruction of the sick tissue. Photosensitizing compounds (chlorophylls and derivatives) existing in the spinach extract have applicability for PDT. This study aimed to develop and characterize the thermoresponsive bioadhesive system composed of Pluronic F127 20.0%- and Carbopol 934P 0.2% (w/w) (FC)-containing chlorophyll-based extract 0.5% (w/w) (FC-Chl). Mechanical and rheological properties, in vitro release, sol-gel transition temperature, and ex vivo permeability of the spinach extract PS components (through pig ear skin) were investigated. Furthermore, photodynamic activity of the system was accessed through uric acid and time-solved measurements. The sol-gel transition temperature obtained for the FC-Chl system was 28.8 ± 0.3 °C. Rheological and texture properties of the platform were suitable for use as a dermatological system, exhibiting easy application and good characteristics of retention in the place of administration. In vitro release studies showed the presence of two distinct mechanisms that reasonably obey the zero-order and first-order kinetics models. PS components presented skin permeability and reached a permeation depth of 830 μm (between the epidermis and dermis). The photodynamic evaluation of the FC-Chl system was effective in the degradation of uric acid. The quantum yield (Φ_Δ¹O₂) and life time (τ¹O₂) of singlet oxygen showed similar values for the spinach extract and the isolated chlorophyll a species in ethanol. These results allowed for the classification of the FC-Chl platform as potentially useful for the delivery of the chlorophyll-based extract in the topic PDT, suggesting that it is worthy for in vivo evaluation.