The Exploitation of pH-Responsive Eudragit-Coated Mesoporous Silica Nanostructures in the Repurposing of Terbinafine Hydrochloride for Targeted Colon Cancer Inhibition: Design Optimization, In Vitro Characterization, and Cytotoxicity Assessment.

Targeted drug delivery is achieving great success in cancer therapy due to its potential to deliver drugs directly to the action site. Terbinafine hydrochloride (TER) is a broad-spectrum anti-fungal drug that has been found to have some potential anti-tumor effects in the treatment of colon cancer. We aimed here to design and develop pH-sensitive Eudragit (Eud)-coated mesoporous silica nanostructures (MSNs) to control drug release in response to changes in pH. The diffusion-supported loading (DiSupLo) technique was applied for loading TER into the MSNs. The formulation was optimized by a D-optimal design, which permits the concurrent assessment of the influence of drug/MSN%, coat concentration, and MSN type on the drug entrapment efficiency (EE) and its release performance. The optimal formula displayed a high EE of 96.49%, minimizing the release in pH 1.2 to 16.15% and maximizing the release in pH 7.4 to 78.09%. The cytotoxicity of the optimal formula on the colon cancer cells HT-29 was higher than it was with TER alone by 2.8-fold. Apoptosis in cancer cells exposed to the optimum formula was boosted as compared to what it was with the plain TER by 1.2-fold and it was more efficient in arresting cells during the G0/G1 and S stages of the cell cycle. Accordingly, the repurposing of TER utilizing Eud/MSNs is a promising technique for targeted colon cancer therapy.

Development, optimization, and evaluation of PEGylated brucine-loaded PLGA nanoparticles.

The application of nanotechnology to drug delivery systems for cancer therapy has progressively received great attention. The most heavily investigated approach is the development of nanoparticles (NPs) utilizing biodegradable and biocompatible polymers such as poly (lactic-co-glycolic acid) (PLGA). These NPs could be further improved by surface modification utilizing a hydrophilic biodegradable polymer such as polyethylene glycol (PEG) to achieve passive targeting. Modified NPs can deliver drugs such as brucine (BRU), which has shown its potential in cancer therapy. The objective of the current investigation was to develop and evaluate the passive targeting of long-circulating PLGA NPs loaded with BRU. NPs were characterized in terms of drug-excipient compatibility studies, including FTIR and DSC; physicochemical evaluations including particle size, zeta potential, morphological evaluation, entrapment efficiency and percentage yield; total serum protein adsorbed onto NP surfaces; and in vitro release of the loaded drug. Factorial design was employed to attain optimal PLGA-loaded NPs. Finally, the in vivo anti-tumor activity of BRU-loaded PLGA NPs was evaluated in tumor-bearing mice. The NPs obtained had smooth surfaces with particle sizes ranged from 94 ± 3.05 to 253 ± 8.7 nm with slightly positive surface charge ranged from 1.09 ± 0.15 to 3.71 ± 0.44 mV. Entrapment of BRU ranged between 37.5 ± 1.8% and 77 ± 1.3% with yields not less than 70.8%. Total protein adsorbed was less than 25.5 µg total protein/1 mg NP. In vitro drug release was less than 99.1% at 168 h. Finally, significant reductions in tumor growth rate and mortality rate were observed for PEG PLGA NP formulations compared to both BRU solution and naked NPs.

Cancer cell-type tropism is one of crucial determinants for the efficient systemic delivery of cancer cell-derived exosomes to tumor tissues.

Exosomes are gaining increasing attention as drug delivery vehicles due to their low toxicity and ability to functionally transfer biological cargos between cells. However, the therapeutic applicability of exosomes is partially hampered by a lack of cell-type specificity. In this study, therefore, we investigated the impact of cell-type tropism on the in vivo systemic delivery of exosomes to tumor tissues. Exosomes derived from murine colorectal cancer cells (C26) (C26-Exos) and murine melanoma cells (B16BL6) (B16BL6-Exos) were collected. In vitro cellular uptake of either autologous (C26) or allogeneic (B16BL6) exosomes by C26 tumor cells was determined. In vivo tumor accumulation of each type of exosomes in mice bearing C26 tumors was monitored with an in vivo imaging system (IVIS). In in vitro studies, autologous C26-Exos were more efficiently taken up by C26 cancer cells, compared to allogeneic B16BL6-Exos. For in vivo studies, exosomes were modified with surface polyethylene glycol (PEG) to improve their circulation lifetimes. Although both types of PEGylated exosomes accumulated in C26-tumor tissue, autologous exosomes were preferentially accumulated within C26-tumor tissue compared to allogeneic exosomes. The increased tumor accumulation of autologous PEGylated exosomes was accompanied by the preferential uptake of exosomes by not only C26-tumor cells but also tumor-associated immune cells. This study implies that cancer cell-type tropism is an important factor in the achievement of tumor cell targeting with cancer cell-derived exosomes.

Liposome co-incubation with cancer cells secreted exosomes (extracellular vesicles) with different proteins expressions and different uptake pathways.

We recently showed that in vitro incubation of cells with liposomes of varying compositions can increase exosome secretion and increase the yield of harvested exosomes (extracellular vesicles, EVs). This might foster their potential therapeutic implementations. In the current study, we investigated the surface proteins and the uptake of the harvested exosomes (EVs) to see if the incubation of cells with liposomes would change the biological properties of these exosomes (EVs). Interestingly, exosomes (EVs) induced by solid cationic liposomes lacked some major exosome marker proteins such as CD9, flotillin-1, annexin-A2 and EGF, and subsequently had lower levels of cellular uptake upon re-incubation with donor cancer cells. However, exosomes (EVs) induced under normal condition and by fluid cationic liposomes, displayed the entire spectrum of proteins, and exhibited higher uptake by the donor cancer cells. Although endocytosis was the major uptake pathway of exosomes (EVs) by tumor cells, endocytosis could occur via more than one mechanism. Higher exosome uptake was observed in donor B16BL6 cells than in allogeneic C26 cells, indicating that donor cells might interact specifically with their exosomes (EVs) and avidly internalize them. Taken together, these results suggest a technique for controlling the characteristics of secreted exosomes (EVs) by incubating donor cancer cells with liposomes of varying physiochemical properties.

A Novel Strategy to Increase the Yield of Exosomes (Extracellular Vesicles) for an Expansion of Basic Research.

Exosomes are tiny extracellular vesicles that are usually harvested in small quantities. Such small yield has been an obstacle for the expansion of the basic research regarding exosome analysis and applications in drug delivery. To increase exosome yield, we attempted to stimulate tumor cells via the addition of liposomes in vitro. Neutral, cationic-bare or PEGylated liposomes were incubated with four different tumor cell lines. The stimulatory effect of liposomal formulations on exosome secretion and cellular uptake propensity of the collected exosome by mother cells or different cells was evaluated. Both neutral and cationic-bare liposomes enhanced exosome secretion in a dose-dependent manner. Fluid cationic liposomes provided the strongest stimulation. Surprisingly, the PEGylation of bare liposomes diminished exosome secretion. Exosomes harvested in the presence of fluid cationic liposomes showed increased cellular uptake, but solid cationic liposomes did not. Our findings indicate that the physicochemical properties of liposomes determine whether they will act as a stimulant or as a depressant on exosome secretion from tumor cells. Liposomal stimulation may be a useful strategy to increase exosome yield, although further preparation to increase the purity of exosomes may be needed. In addition, fine-tuning of the biological properties of induced exosomes could be achieved via controlling the physicochemical properties of the stimulant liposomes.

Encapsulation in a rapid-release liposomal formulation enhances the anti-tumor efficacy of pemetrexed in a murine solid mesothelioma-xenograft model.

We recently developed a PEG-coated liposome encapsulating the anti-folate drug pemetrexed (PMX). Such liposomal formulations have shown potent cytotoxic effects against malignant pleural mesothelioma (MPM) cells in vitro. In the present study, we investigated the pharmacokinetics, bio-distribution and in vivo anti-tumor efficacy of two liposomal PMX formulations with different drug release rates in a murine mesothelioma-xenograft model. Liposomes with different PMX release rates were prepared via manipulating liposomal membrane fluidity through incorporating either a solid-phase (HSPC) or a fluid-phase (POPC) phospholipid. Both liposomal PMX formulations showed prolonged plasma pharmacokinetics and were accumulated to a similar extent in tumors and other tissues, presumably, due to surface modification with polyethylene glycol (PEG). In a murine mesothelioma-xenograft model, interestingly, PMX encapsulated in a fast-release POPC liposome produced superior tumor growth suppression compared with either free PMX or PMX encapsulated in a slow-release HSPC liposome. Such in vivo anti-tumor efficacy was accomplished mainly by a potent induction of apoptosis within tumor tissue by the released PMX from POPC liposomes. Our results clearly emphasize the therapeutic efficacy of liposomal PMX over free PMX in conquering aggressive solid tumors such as malignant mesothelioma. A guarantee of the targeted delivery of PMX to tumor cells helps overcome some of the major shortcomings encountered with the use of free PMX.