Improved water solubility and photodynamic activity of hydroxy-modified porphyrins by complexation with cyclodextrin

Extracellular Vesicles Comprising Carborane Prepared by a Host Exchanging Reaction as a Boron Carrier for Boron Neutron Capture Therapy

With their low immunogenicity and excellent deliverability, extracellular vesicles (EVs) are promising platforms for drug delivery systems. In this study, hydrophobic molecule loading techniques were developed via an exchange reaction based on supramolecular chemistry without using organic solvents that can induce EV disruption and harmful side effects. To demonstrate the availability of an exchanging reaction to prepare drug-loading EVs, hydrophobic boron cluster carborane (CB) was introduced to EVs (CB@EVs), which is expected as a boron agent for boron neutron capture therapy (BNCT). The exchange reaction enabled the encapsulation of CB to EVs without disrupting their structure and forming aggregates. Single-particle analysis revealed that an exchanging reaction can uniformly introduce cargo molecules to EVs, which is advantageous in formulating pharmaceuticals. The performance of CB@EVs as boron agents for BNCT was demonstrated in vitro and in vivo. Compared to L-BPA, a clinically available boron agent, and CB delivered with liposomes, CB@EV systems exhibited the highest BNCT activity in vitro due to their excellent deliverability of cargo molecules via an endocytosis-independent pathway. The system can deeply penetrate 3D cultured spheroids even in the presence of extracellular matrices. The EV-based system could efficiently accumulate in tumor tissues in tumor xenograft model mice with high selectivity, mainly via the enhanced permeation and retention effect, and the deliverability of cargo molecules to tumor tissues in vivo enhanced the therapeutic benefits of BNCT compared to the L-BPA/fructose complex. All of the features of EVs are also advantageous in establishing anticancer agent delivery platforms.

Photoacoustic Imaging Using Polysaccharide-Porphyrin Complexes by Photoirradiation at Long Wavelengths

Photoacoustic (PA) imaging is a novel biological imaging technique with superior depth resolution compared to fluorescence imaging. The efficacy of PA imaging depends on contrast agents that possess considerable absorbance at longer wavelengths, coupled with high permeability in biological tissue and minimal fluorescence, achieved through mitigating aggregation-caused quenching (ACQ) that attenuates PA intensity. Despite the successful transfer of porphyrin 2 featuring amino moieties from polysaccharides to liposomes, most of 2 incorporated within λ-carrageenan (CGN-2 complex) remained in CGN under acidic lysosomal conditions (pH 5.0). Consequently, the CGN-2 complex exhibited a strong PA signal under 680 nm photoirradiation in Colon26 cells owing to the ACQ of 2. Moreover, the PA intensity of the CGN-2 complex was further enhanced under 780 nm photoirradiation owing to the increased absorbance at 780 nm facilitated by the redshift of the Q-band at pH 5.0.

HER-2-Targeted Boron Neutron Capture Therapy with Carborane-integrated Immunoliposomes Prepared via an Exchanging Reaction

Boron neutron capture therapy (BNCT) is a promising modality for cancer treatment because of its minimal invasiveness. To maximize the therapeutic benefits of BNCT, the development of efficient platforms for the delivery of boron agents is indispensable. Here, carborane-integrated immunoliposomes were prepared via an exchanging reaction to achieve HER-2-targeted BNCT. The conjugation of an anti-HER-2 antibody to carborane-integrated liposomes successfully endowed these liposomes with targeting properties toward HER-2-overexpressing human ovarian cancer cells (SK-OV3); the resulting BNCT activity toward SK-OV3 cells obtained using the current immunoliposomal system was 14-fold that of the l-BPA/fructose complex, which is a clinically available boron agent. Moreover, the growth of spheroids treated with this system followed by thermal neutron irradiation was significantly suppressed compared with treatment with the l-BPA/fructose complex.

"On-Off" Switching of Functional Guest Molecules via Exchange of Natural Product Solubilizing Agents

For the development of delivery systems, the solubilization of hydrophobic guest molecules in water is an important yet challenging task. This can be achieved by preparing stable aqueous solutions with a high concentration of guest molecules using a natural product as a solubilizing agent and a mechanochemical high-speed vibration milling apparatus as a solubilizing method. Various solubilizing agent-guest molecule complexes can be obtained via the exchange between solubilizing agents, which enables the "on-off" switching of the properties of functional guest molecules, such as fluorescence intensity, and photodynamic activity. In the exchange method, guest molecules can transfer into cell membranes such as lysosomes and exosomes. Therefore, the exchange method of the solubilizing agents not only creates novel solubilizing agent-guest molecule complexes but also is applied to drug delivery systems.

HER-2-targeted boron neutron capture therapy using an antibody-conjugated boron nitride nanotube/β-1,3-glucan complex

The development of boron agents with integrated functionality, including biocompatibility, high boron content, and cancer cell targeting, is desired to exploit the therapeutic efficacy of boron neutron capture therapy (BNCT). Here, we report the therapeutic efficacy of BNCT using a HER-2-targeted antibody-conjugated boron nitride nanotube/β-1,3-glucan complex. The anticancer effect of BNCT using our system was 30-fold that of the clinically available boron agent l-BPA/fructose complex.

Fluorescence Turn-on of Tetraphenylethylene Derivative by Transfer from Cyclodextrin to Liposomes, HeLa Cells, and E. coli

Herein, trimethyl-β-cyclodextrin (TMe-β-CDx) and γ-cyclodextrin (γ-CDx) could dissolve a tetraphenylethylene derivative (TPE-OH₄ ) in water through high-speed vibration milling. The fluorescence intensity of the TMe-β-CDx-TPE-OH₄ complex was much higher than that of the γ-CDx-TPE-OH₄ complex, as the rotation of the central C=C double bond of TPE-OH₄ after photoactivation was inhibited in a smaller TMe-β-CDx cavity in comparison with the γ-CDx cavity. In contrast, the fluorescence intensity of the γ-CDx-TPE-OH₄ complex was very weak; nevertheless, it increased after the addition of liposomes due to the transfer of TPE-OH₄ from the γ-CDx cavity to the lipid membrane as a "turn-on" phenomenon. Furthermore, to apply temperature sensor, it was demonstrated that the fluorescence intensity in the liposomes depended on the phase-transition temperature. By using the fluorescence turn-on phenomenon, TPE-OH₄ could detect the presence of HeLa cells and E. coli by fluorescence.

Development of a Water-Dispersible Supramolecular Complex of Polyphenol with Polypeptides for Attenuation of the Allergic Response using a Mechanochemical Strategy

The prevalence of allergic disorders has increased worldwide in recent decades. Polyphenols, including resveratrol and curcumin, are posited to have potential as therapeutic agents for allergy; however, their use has been limited by poor water solubility. Accordingly, a highly concentrated, water dispersible, supramolecular complexes of polyphenols with polypeptides (poly-L-lysine, poly-γ-glutamic acid) and gelatin using high-speed vibration milling are developed. The complex exhibited resistance to photobleaching and thermal radiation. Treatment of a rat basophilic leukemia cell line (RBL-2H3) with polypeptide complexes containing resveratrol is suppressed allergic responses in vitro. Moreover, aerosolized administration of polypeptide complexes is demonstrated excellent bioavailability and inhibition of immediate hypersensitivity reactions in ear tissue in vivo. Furthermore, the method avoids the use of organic solvent and therefore reduces undesirable biological responses.

Formulation of water-dispersible hydrophobic compound nanocomplexes with polypeptides via a supramolecular approach using a high-speed vibration milling technique

Polypeptides were used to solubilize functional hydrophobic molecules via a high-speed vibrational milling method. Poly-l-lysine and poly-γ-glutamic acid, which are polypeptides, were able to prepare more highly concentrated water-dispersible complexes of hydrophobic compounds, including fullerenes, organic dyes, and porphyrin derivatives, than conventional water solubilizers, such as cyclodextrins and pullulan. In addition, the polypeptide systems endowed the complexes with long-term stability and resistance against thermal stress, which is advantageous for industrial applications. Furthermore, complexes of polypeptides and porphyrin derivatives showed a photodynamic activity against cancer cells, and the current system improved the dispersibility and storability of guest molecules without compromising their functionality.

Theranostic Agent Combining Fullerene Nanocrystals and Gold Nanoparticles for Photoacoustic Imaging and Photothermal Therapy

Developing photoactivatable theranostic platforms with integrated functionalities of biocompatibility, targeting, imaging contrast, and therapy is a promising approach for cancer diagnosis and therapy. Here, we report a theranostic agent based on a hybrid nanoparticle comprising fullerene nanocrystals and gold nanoparticles (FGNPs) for photoacoustic imaging and photothermal therapy. Compared to gold nanoparticles and fullerene crystals, FGNPs exhibited stronger photoacoustic signals and photothermal heating characteristics by irradiating light with an optimal wavelength. Our studies demonstrated that FGNPs could kill cancer cells due to their photothermal heating characteristics in vitro. Moreover, FGNPs that are accumulated in tumor tissue via the enhanced permeation and retention effect can visualize tumor tissue due to their photoacoustic signal in tumor xenograft model mice. The theranostic agent with FGNPs shows promise for cancer therapy.

Effect of meso Positioned Substituents on the Stability and Photodynamic Activity of Lipid-Membrane-Incorporated Porphyrin Derivatives

Here, we prepared aqueous solutions of lipid-membrane incorporated tetraarylporphyrins and tetrapyridylporphyrin (LMIPors) by the injection method using dimethyl sulfoxide. The porphyrins with proton-donor groups at the meso position afforded stable aqueous solutions of LMIPors. However, although tetrakis(carboxyphenyl)porphyrin was scarcely incorporated in lipid membranes, it was soluble in water. Among these LMIPors, the photodynamic activity of tetrakis(hydroxyphenyl)porphyrin was higher than that of tetrakis(aminophenyl)porphyrin. This was attributed to the self-aggregation of a part of tetrakis(aminophenyl)porphyrin in the liposomes, which induced self-quenching and the consequent decrease of its photodynamic activity.

Unsymmetrical, monocarboxyalkyl meso-arylporphyrins in the photokilling of breast cancer cells using permethyl-β-cyclodextrin as sequestrant and cell uptake modulator

In the search for photosensitizers with chemical handles to facilitate their integration into complex drug delivery nanosystems, new, unsymmetrically substituted, water insoluble meso-tetraphenylporphyrin and meso-tetra(m-hydroxyphenyl)porphyrin derivatives bearing one carboxyalkyl side chain were synthesized. Permethyl-β-cyclodextrin (pMβCD) was their ideal monomerizing host and highly efficient shuttle to transfer them into water. New assembly modes of the extremely stable (K_binding > 10¹² M^-2) 2:1 complexes were identified. The complexes are photostable and do not disassemble in FBS-containing cell culture media for 24 h. Incubation of breast cancer MCF-7 cells with the complexes results in intense intracellular fluorescence, strongly enhanced in the endoplasmic reticulum (ER), high photokilling efficiency (~90%) and low dark toxicity. pMβCD stands out as a very capable molecular isolator of mono-carboxyalkyl-arylporphyrins that increases uptake and modulates their localization in the cells. The most efficient porphyrins are envisaged as suitable photosensitizers that can be linked to biocompatible drug carriers for photo- and chemo-therapy applications.

Drug delivery systems for the photodynamic application of two photosensitizers belonging to the porphyrin family

Photodynamic therapy involves the concomitant action of three components, light with an appropriate wavelength, molecular oxygen, and a molecule, able to absorb an electromagnetic radiation, called photosensitizer (PS). A fundamental aspect is the bioavailability of the PS that is directly related to some physicochemical properties of the PS itself as it should feature a certain degree of lipophilicity to easily cross the cell membrane, however, at the same time, should be sufficiently water-soluble to navigate in the bloodstream. Consequently, the use of a system for drug delivery becomes essential when photosensitizers with a high degree of lipophilicity are considered. In this work, we present three different drug delivery systems, microemulsions, emulsions and liposomes all capable of carrying a PS belonging to the porphyrin family: the tetraphenyl porphyrin (TPP) and the 4-hydroxyphenyl porphyrin (THPP), which show a relevant different degree of lipophilicity. A series of microemulsions (ME) and emulsions (E) were prepared, among which two formulations, one for THPP and one for TPP, have been chosen. The stability of these two carriers was monitored over time and under various temperature conditions. With the same criteria, two liposomal formulations have been also identified and analyzed. The four formulations mentioned above (one ME, one E and two liposomes) have been tested on SKOV3 tumor cell line comparing the photodynamic activity of the porphyrin formulations versus the aqueous/organic (DMSO) solution of the same two PSs. The results show that all the formulations have proved to be excellent carriers and that the liposomal formulation enhance the photodynamic efficacy of both porphyrins.

Photodynamic therapy using self-assembled nanogels comprising chlorin e6-bearing pullulan

With minimal invasiveness and spatiotemporal therapeutic effects, photodynamic therapy is one of the most promising candidates for cancer treatment. Here, we developed a facile self-assembled nanogel using photosensitizer-grafted polysaccharides called chlorin e6-bearing pullulan. Chlorin e6 is used as a photosensitizer in cancer therapy. The anti-cancer effect of photodynamic therapy with our nanogel system was 780 times higher than that of the commercially available photosensitizer Photofrin. Finally, we demonstrated that actively growing cancer cell spheroids can be completely suppressed after treatment. Our system could efficiently induce tumor regression in tumor xenograft mice.

Water Solubilization and Thermal Stimuli-Triggered Release of Porphyrin Derivatives Using Thermoresponsive Polysaccharide Hydroxypropyl Cellulose for Mitochondria-Targeted Photodynamic Therapy

With minimal invasiveness and spatiotemporal therapeutic effects, photodynamic therapy is one of the most elegant strategies for achieving effective tumor therapy. Herein, a facile preparation and thermal process-triggered release of water-soluble photosensitizer 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (THPP) has been developed using a thermoresponsive polysaccharide, hydroxypropyl cellulose. Current systems using hydroxypropyl cellulose enable manipulation of the loading capacity of THPP into a polymer matrix and the size of the complex by varying the temperature of the solution in preparation. Furthermore, current systems have enabled the release of THPP using a heating process, mimicking the surrounding of mitochondria, and have resulted in THPP potency as a mitochondria-targeted photodynamic therapy.

Mechanism toward Turn-on of Polysaccharide-Porphyrin Complexes for Fluorescence Probes and Photosensitizers in Photodynamic Therapy in Living Cells

β-(1,3-1,6)-D-Glucan, λ-carrageenan, tamarind gum, and pullulan can dissolve various porphyrin derivatives via the formation of complexes in water using a high-speed vibration milling method. The aqueous solutions of the resulting complexes exhibit long-term stability. Despite the adverse effects of the self-quenching process, notable fluorescence and improved photodynamic activity of the polysaccharide-complexed porphyrin derivatives were observed in the presence of liposomes, micelles, cyclodextrins, and HeLa cells. It was noted that the type of porphyrins was more important than the type of polysaccharides present in the complex. Porphyrin self-aggregates were monodispersed in the lipid membranes of the liposomes and lysosomes. The polysaccharide-complexed porphyrin derivatives showed increased photodynamic activity toward HeLa cells under photoirradiation between 610 and 740 nm.