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.

Highly loaded deoxypodophyllotoxin nano-formulation delivered by methoxy polyethylene glycol-block-poly (D,L-lactide) micelles for efficient cancer therapy

Cancer is a kind of malignant diseases that threatens human health and the research application of anti-tumor drug therapeutics is growingly always been focused on. Many new compounds with great anticancer activity were synthesized but cannot be hard to be developed into clinical use due to its poor water solubility. Deoxypodophyllotoxin (DPT) is just an example. We develop lyophilized Deoxypodophyllotoxin (DPT) loaded polymeric micelles using methoxy polyethylene glycol-block-Poly (D, L-lactide) (mPEG-PLA). DPT-PM freeze-dried powder was successfully prepared using optimized formulation. mPEG-PLA was added to hydration media before hydrating as cryoprotectants. The freeze-dried powder exhibited white pie-solid without collapsing, and the particle size of DPT-PM reconstituted with water was about 20-35 nm. The entrapment efficiency of the reconstituted solution was 98%, which shows no differences with the micelles before lyophilization. In-vitro cytotoxicity and cellular uptake studies showed that DPT-PM has a higher degree of cytotoxicity comparing with DPT and mPEG-PLA micelles and uptake of mPEG-PLA was concentration and time-dependent. In vivo characterization of DPT-PM was done for pharmacokinetics behaviors, antitumor activity and safety. The obtained results showed significant improvement in plasma clearance bioavailability (p <0.05) and prolonged blood circulation time comparing with DPT-HP-β-CD. Moreover, mPEG-PLA micelles had a better degree of anti-tumor efficacy, this was due to better accumulation of mPEG-PLA in tumor cell via enhanced permeability and retention (EPR) effect. Therefore, DPT-PM has great clinical value, and can be expected to be a novel antitumor preparation.

Study on intracellular delivery of liposome encapsulated quantum dots using advanced fluorescence microscopy

Quantum dots increasingly gain popularity for in vivo applications. However, their delivery and accumulation into cells can be challenging and there is still lack of detailed information. Thereby, the application of advanced fluorescence techniques can expand the portfolio of useful parameters for a more comprehensive evaluation. Here, we encapsulated hydrophilic quantum dots into liposomes for studying cellular uptake of these so-called lipodots into living cells. First, we investigated photophysical properties of free quantum dots and lipodots observing changes in the fluorescence decay time and translational diffusion behaviour. In comparison to empty liposomes, lipodots exhibited an altered zeta potential, whereas their hydrodynamic size did not change. Fluorescence lifetime imaging microscopy (FLIM) and fluorescence correlation spectroscopy (FCS), both combined with two-photon excitation (2P), were used to investigate the interaction behaviour of lipodots with an insect epithelial tissue. In contrast to the application of free quantum dots, their successful delivery into the cytosol of salivary gland duct cells could be observed when applying lipodots. Lipodots with different lipid compositions and surface charges did not result in considerable differences in the intracellular labelling pattern, luminescence decay time and diffusion behaviour. However, quantum dot degradation after intracellular accumulation could be assumed from reduced luminescence decay times and blue-shifted luminescence signals. In addition to single diffusing quantum dots, possible intracellular clustering of quantum dots could be assumed from increased diffusion times. Thus, by using a simple and manageable liposome carrier system, 2P-FLIM and 2P-FCS recording protocols could be tested, which are promising for investigating the fate of quantum dots during cellular interaction.

Photodynamic Activity of Fullerene Derivatives Solubilized in Water by Natural-Product-Based Solubilizing Agents

Water-soluble fullerenes prepared by using solubilizing agents based on natural products are promising photosensitizers for photodynamic therapy. Cyclodextrin, β-1,3-glucan, lysozyme, and liposomes can stably solubilize not only C₆₀ and C₇₀ , but also some C₆₀ derivatives in water. To improve the solubilities of fullerenes, specific methods have been developed for each solubilizing agent. Water-soluble C₆₀ and C₇₀ exhibit photoinduced cytotoxicity under near-ultraviolet irradiation, but not at wavelengths over 600 nm, which are the appropriate wavelengths for photodynamic therapy. However, dyad complexes of solubilized C₆₀ derivatives combined with light-harvesting antenna molecules improve the photoinduced cytotoxicities at wavelengths over 600 nm. Furthermore, controlling the fullerene and antenna molecule positions within the solubilizing agents affects the performance of the photosensitizer.

Formation of lipid membrane-incorporated small π-molecules bearing hydrophilic groups

Lipid membrane-incorporated π-conjugated guest molecules (LMIGs) have been classified into four categories, including stable LMIGs, the precipitation or dissolution of some of the guest molecules from the LMIGs and the formation of small aggregates.

Lipophilic prodrug conjugates allow facile and rapid synthesis of high-loading capacity liposomes without the need for post-assembly purification

Dihydropyridopyrazoles are simplified synthetic analogues of podophyllotoxin that can effectively mimic its molecular scaffold and act as potent mitotic spindle poisons in dividing cancer cells. However, despite nanomolar potencies and ease of synthetic preparation, further clinical development of these promising anticancer agents is hampered due to their poor aqueous solubility. In this article, we developed a prodrug strategy that enables incorporation of dihydropyridopyrazoles into liposome bilayers to overcome the solubility issues. The active drug was covalently connected to either myristic or palmitic acid anchor via carboxylesterase hydrolyzable linkage. The resulting prodrugs were self-assembled into liposome bilayers from hydrated lipid films using ultrasound without the need for post-assembly purification. The average particle size of the prodrug-loaded liposomes was about 90 nm. The prodrug incorporation was verified by differential scanning calorimetry, spectrophotometry and gel filtration reaching maximum at 0.3 and 0.35 prodrug/lipid molar ratios for myristic and palmitic conjugates, respectively. However, the ratio of 0.2 was used in the particle size and biological activity experiments to maintain long-term stability of the prodrug-loaded liposomes against phase separation during storage. Antiproliferative activity was tested against HeLa and Jurkat cancer cell lines in vitro showing that the liposomal prodrug retained antitubulin activity of the parent drug and induced apoptosis-mediated cancer cell death. Overall, the established data provide a powerful platform for further clinical development of dihydropyridopyrazoles using liposomes as the drug delivery system.

Lipid-membrane-incorporated hydrophobic photochromic molecules prepared by the exchange method using cyclodextrins

It was found that the exchange method for the preparation of lipid-membrane-incorporated guest molecules was applicable to not only fullerenes but also other hydrophobic molecules such as azobenzene and stilbene.

Lipid membranes as solvents for carbon nanoparticles

Fullerene is scarcely soluble in most solvents, including alkanes. Yet, it has been shown that C60 dissolves in lipid bilayers, whose interior is chemically identical to alkanes. Here, we use molecular simulations to explain why lipid bilayers are better than alkanes at dissolving fullerene clusters. Fullerene aggregation is driven by entropy, but enthalpic contributions determine the difference between alkanes and bilayers. Surprisingly, confinement and chain alignment in the bilayer do not affect fullerene aggregation, while solvent density and the perturbation of solvent-solvent interactions are key factors.

Dynamic behaviour of giant unilamellar vesicles induced by the uptake of [70]fullerene

We have directly observed the processes involved in a C₇₀-exchange reaction from γ-cyclodextrin cavities to lipid membranes using GUVs by phase contrast microscopy.

Liposome formulation of fullerene-based molecular diagnostic and therapeutic agents

Fullerene medicine is a new but rapidly growing research subject. Fullerene has a number of desired structural, physical and chemical properties to be adapted for biological use including antioxidants, anti-aging, anti-inflammation, photodynamic therapy, drug delivery, and magnetic resonance imaging contrast agents. Chemical functionalization of fullerenes has led to several interesting compounds with very promising preclinical efficacy, pharmacokinetic and safety data. However, there is no clinical evaluation or human use except in fullerene-based cosmetic products for human skincare. This article summarizes recent advances in liposome formulation of fullerenes for the use in therapeutics and molecular imaging.

A photo-triggerable drug carrier based on cleavage of PEG lipids by photosensitiser-generated reactive singlet oxygen

To circumvent the limitations of polyethylene glycol (PEG) modified carriers, a photo-triggerable liposome was prepared which was modified by cholesterol derivatives via a cleavable vinyl ether linkage so that the PEGylated coating can be efficiently removed by a photoactivated fullerene. After the photocleavage of the PEG moiety, the intracellular uptake of the photo-triggerable liposome improved.

Cyclodextrin complexed [60]fullerene derivatives with high levels of photodynamic activity by long wavelength excitation

We have evaluated the photodynamic activities of C60 derivative·γ-cyclodextrin (γ-CDx) complexes and demonstrated that they were significantly higher than those of the pristine C60 and C70·γ-CDx complexes under photoirradiation at long wavelengths (610-720 nm), which represent the optimal wavelengths for photodynamic therapy (PDT). In particular, the cationic C60 derivative·γ-CDx complex had the highest photodynamic ability because the complex possessed the ability to generate high levels of (1)O2 and provided a higher level of intracellular uptake. The photodynamic activity of this complex was greater than that of photofrin, which is the most widely used of the known clinical photosensitizers. These findings therefore provide a significant level of information toward the optimization of molecular design strategies for the synthesis of fullerene derivatives for PDT.

Advantages and potential of lipid-membrane-incorporating fullerenes prepared by the fullerene-exchange method

Lipid-membrane-incorporating C(60) and C(70) (LMIC(60) and LMIC(70)) were prepared by the fullerene-exchange reaction from the γ-cyclodextrin cavity to vesicles (we call this method the "exchange method"). An advantage of this method is that the ratios of [C(60)]/[lipids] and [C(70)]/[lipids] can be arbitrarily controlled by adjusting the ratios of the fullerenes and liposome. The maximum ratio (30 mol%) obtained was approximately 14 and 100 times higher than those achieved for LMIC(60) and LMIC(70) , respectively, that were prepared by the classical method, which we call the "premixing method" (dissolving lipids and C(60) or C(70) in chloroform, followed by concentration and extraction with water). Furthermore, the stabilities and photodynamic activities of the LMIC(60) and LMIC(70) solutions prepared by the exchange method were shown to be much higher than those prepared by the premixing method. That is, the exchange method was found to be superior to the premixing method as a preparative method of LMIC(60) and LMIC(70) for applications in photomedical and photomaterials chemistry.

Location of [60]fullerene incorporation in lipid membranes

We confirmed that most C(60) fullerene units are located in the hydrophobic core of the lipid bilayer membrane in water-soluble lipid membrane incorporated C(60) (LMIC(60)) complexes using differential scanning calorimetry (DSC) and (13)C NMR spectra in the presence of radical labels.