Membrane-Loaded Doxorubicin Liposomes Based on Ion-Pairing Technology with High Drug Loading and pH-Responsive Property

Reversible protein complexes as a promising avenue for the development of high concentration formulations of biologics

High concentration formulations have become an important pre-requisite in the development of biological drugs, particularly in the case of subcutaneous administration where limited injection volume negatively affects the administered dose. In this study, we propose to develop high concentration formulations of biologics using a reversible protein-polyelectrolyte complex (RPC) approach. First, the versatility of RPC was assessed using different complexing agents and formats of therapeutic proteins, to define the optimal conditions for complexation and dissociation of the complex. The stability of the protein was investigated before and after complexation, as well as upon a 4-week storage period at various temperatures. Subsequently, two approaches were selected to develop high concentration RPC formulations: first, using up-concentrated RPC suspensions in aqueous buffers, and second, by generating spray-dried RPC and further resuspension in non-aqueous solvents. Results showed that the RPC concept is applicable to a wide range of therapeutic protein formats and the complexation-dissociation process did not affect the stability of the proteins. High concentration formulations up to 200 mg/mL could be achieved by up-concentrating RPC suspensions in aqueous buffers and RPC suspensions in non-aqueous solvents were concentrated up to 250 mg/mL. Although optimization is needed, our data suggests that RPC may be a promising avenue to achieve high concentration formulations of biologics for subcutaneous administration.

Alpha-tocopheryl succinate and doxorubicin-loaded liposomes improve drug uptake and tumor accumulation in a murine breast tumor model

Liposomes composed of a rigid bilayer have high plasma stability; however, they can be challenged in efficacy due to complications in releasing the encapsulated drug as well as being internalized by the tumor cell. On the other hand, fusogenic liposomes may fuse with the plasmatic membrane and release encapsulated material directly into the cytoplasm. In a previous study, fusogenic liposomes composed of alpha-tocopheryl succinate (TS) and doxorubicin (DOX) were developed (pHSL-TS-DOX). These stabilized tumor growth and reduced toxicity compared to a commercial formulation. In the present study, we investigated whether cellular uptake or DOX accumulation in the tumor could justify the better performance of the pHSL-TS-DOX formulation. Release, deformability, and DOX plasmatic concentration studies were also carried out. pHSL-TS-DOX showed an adequate release profile and demonstrated characteristics of a deformable formulation. Data from apoptosis, cell cycle, and nuclear morphology studies have shown that the induction of cell death caused by pHSL-TS-DOX occurred more quickly. Higher DOX cellular uptake and tumor accumulation were observed when pHSL-TS-DOX was administered, demonstrating better drug delivery capacity. Therefore, better DOX uptake as well as tumor accumulation explain the great antitumor activity previously demonstrated for this formulation.

From Design to Study of Liposome-Driven Drug Release Part 1: Impact of Temperature and pH on Environment

The marketed drug Doxorubicin (DOX) and the promising anti-cancer agent 9-(N-piperazinyl)-5-methyl-12(H)-quino[3,4-b][1,4]benzothiazinium chloride (9-PBThACl) were used to prepare and compare a range of liposomal delivery systems based on dipalmitoylphosphatidylcholine (DPPC). Liposome-assisted drug release was examined using the spectrophotometric method. In order to provide in vitro release characteristics of liposomal conjugates (L_DPPC/drug vs. L_{DPPC/drug/drug}) as well as to evaluate the impact of temperature and pH buffering on the conformation/polarity of the phospholipid bilayer, the encapsulation efficiency of the liposomes entrapping 9-PBThACl and DOX was calculated. In fact, some competition between the investigated molecules was noticed during the entrapment process because relatively high values of the encapsulation efficiency were observed only for the liposomal complexes containing one trapped drug molecule. An averaged absorbance value enabled us to indicate the pH value of the environment (pH ≈ 6.8), at which the physicochemical property profiles of the liposomal complexes were noticeably changed. Moreover, the operational factors limiting the drug release kinetics from the produced liposomes were mathematically modeled. First-order and Bhaskas models ensured satisfactory compliance with the experimental data for the liposomal complexes buffered at pH values of 5.50, 6.00, and 7.40, respectively.

Ligustrazine-Loaded Borneol Liposome Alleviates Cerebral Ischemia-Reperfusion Injury in Rats

Our team's pharmacological and clinical trials proved that ligustrazine/borneol spray had a definite effect on ischemic stroke (IS). To solve the shortcomings of ligustrazine/borneol spray, such as low bioavailability, short half-life, and poor compatibility between borneol and ligustrazine, ligustrazine-loaded borneol liposomes (LIP@TMP) were successfully prepared by a thin-film ultrasonication method. The average particle size of LIP@TMP was 282.4 ± 3.6 nm, the drug loading rate was 14.5 ± 0.6%, and the entrapment efficiency was 42.7 ± 1.0%, which had excellent stability and sustained release ability. In addition, live/dead fluorescent staining and the CCK-8 test confirmed that LIP@TMP had good biocompatibility. Moreover, middle cerebral artery occlusion (MCAO) rat model experiments further demonstrated that LIP@TMP could significantly alleviate cerebral ischemia and reperfusion injury by improving neurological scores, reducing cerebral infarct volume, promoting neurogenesis, inhibiting inflammation, and reducing tissue damage. In addition, LIP@TMP enhanced neuronal marker doublecortin (DCX) and neuronal nuclei (NEUN), inhibited inflammatory factors (TNF-α and IL-1β), and reduced apoptosis signal molecules (TUNEL and caspase-3). The findings of this study suggested that the prepared LIP@TMP had tremendous potential for the treatment of cerebral ischemia.

Synergistic Antitumor Efficacy Mediated by Liposomal Co-Delivery of Polymeric Micelles of Vinorelbine and Cisplatin in Non-Small Cell Lung Cancer

PURPOSE

Non-small cell lung cancer (NSCLC) is an aggressive tumor with high mortality and poor prognosis. In this study, we designed a liposome encapsulating polymeric micelles (PMs) loaded with vinorelbine (NVB) and cis-diamminedichloroplatinum (II) (cisplatin or CDDP) for the treatment of NSCLC.

MATERIALS AND METHODS

Sodium poly(α-l-glutamic acid)-graft-methoxy-polyethylene glycol (PLG-G-PEG5K) was used to prepare NVB-loaded NVB-PMs and CDDP-loaded CDDP-PMs that were co-encapsulated into liposomes by a reverse evaporation method, yielding NVB and CDDP co-delivery liposomes (CoNP-lips) composed of egg phosphatidyl lipid-80/cholesterol/DPPG/DSPE-mPEG2000 at a molar ratio of 52:32:14:2. The CoNP-lips were characterized in terms of particle size, zeta potential, drug content, encapsulation efficiency, and structural properties. Drug release by the CoNP-lips as well as their stability and cytotoxicity was evaluated in vitro, and their antitumor efficacy was assessed in a mouse xenograft model of Lewis lung carcinoma cell-derived tumors.

RESULTS

CoNP-lips had a spherical shape with uniform size distribution; the average particle size was 162.97±9.06 nm, and the average zeta potential was -13.02±0.22 mV. In vitro cytotoxicity analysis and the combination index demonstrated that the CoNP-lips achieved a synergistic cytotoxic effect at an NVB:CDDP weight ratio of 2:1 in an NSCLC cell line. There was sustained release of both drugs from CoNP-lips. The pharmacokinetic analysis showed that CoNP-lips had a higher plasma half-life than NP solution, with 6.52- and 8.03-fold larger areas under the receiver operating characteristic curves of NVB and CDDP. CoNP-lips showed antitumor efficacy in tumor-bearing C57BL/6 mice and drug accumulation in tumors via the enhanced permeability and retention effect.

CONCLUSION

CoNP-lips are a promising formulation for targeted therapy in NSCLC.

Enhanced in vitro antitumor efficacy of a polyunsaturated fatty acid-conjugated pH-responsive self-assembled ion-pairing liposome-encapsulated prodrug

The development of clinical chemotherapeutics is always challenging due to the toxicity and side effects of drugs not only for tumor cells but also for normal cells. Therefore, nano-drug delivery systems and prodrug strategies have been applied to address this challenge. Herein, we report a liposome-encapsulated small-molecule prodrug nanosystem, self-assembled by doxorubicin (DOX) and mixed polyunsaturated fatty acid (MPUFA) ion-pairing (MPUFAs-DOX@Liposomes), which has a high omega-3 PUFA content. The increased lipophilicity of ion-paired MPUFAs-DOX can significantly improve the drug loading efficiency (∼97%). Electrostatic interaction, the hydrophobic effect and hydrogen bonding between the ion-pairing agents led to superior pH-responsive release of DOX from liposomes over DOX-loaded liposomes (DOX@Liposomes), with a more rapid release rate at pH 5.0 than at pH 7.4, which is beneficial for decreasing the toxicity of DOX under physiological conditions. Finally, the in vitro antitumor effects were investigated for two tumor cell types, A549 and MCF-7, and the results demonstrated that MPUFAs-DOX@Liposomes showed the highest cytotoxicity compared with free DOX and DOX@Liposomes because of the ready uptake under the effect of PUFAs. Hence, liposomes loaded with ion-paired MPUFAs-DOX is a promising formulation for combination cancer therapy.

Aprepitant Intravenous Emulsion Based on Ion Pairing/Phospholipid Complex for Improving Physical and Chemical Stability During Thermal Sterilization

An aprepitant (APT) cholesteryl hemisuccinate (CHEMS) ion pair complex emulsion (AIPE) with high lecithin content was prepared to improve sterilization stability through the film dispersion homogenization method; therefore, it could be a promising delivery system of APT. Medium-chain triglycerides (MCT) was selected as the oil phase to improve the solubility and stability of APT in oil phase. DSC, XRD, FT-IR, and ¹H-NMR spectroscopies confirmed that the APT-CHEMS ion pair (AIP) was formed between CHEMS and APT. The formation of AIP significantly increased the hydrophobicity of APT, allowing it to be completely embedded in the oil phase core to improve chemical stability and decrease hydrolysis of APT in the water phase. Also, CHEMS had a strong affinity with lecithin and could stabilize lipid membranes, forming a stronger and thicker interface membrane to increase the physical stability of AIPE. As a result, AIPE could withstand autoclaving at 120°C for 8 min without any change of particle size or content. Furthermore, AIPE with a potential of - 53.4 mV remained stable through spatial repulsion during sterilization. The encapsulation efficiency of AIPE was over 90% and the particle size was 106.8 ± 65.62 nm(0.286). Pharmacokinetic study in rats was comparable with that of CINVANTI which yielded a relative bioavailability of 114.31% indicating that the AIPE had similar pharmacokinetic processes in vivo with the analog of CINVANTI®. The AUC0-t of the AIPE was 4.31-fold that of the APT solution.

Alpha-tocopheryl succinate improves encapsulation, pH-sensitivity, antitumor activity and reduces toxicity of doxorubicin-loaded liposomes

Doxorubicin (DOX) plays an important role in cancer treatment; however, high cardiotoxicity and low penetration in solid tumors are the main limitations of its use. Liposomal formulations have been developed to attenuate the DOX toxicity, but the technological enhancement of the liposomal formulation as well as the addition of another agent with antitumor properties, like alpha-tocopheryl succinate (TS), a semi-synthetic analog of vitamin E, could certainly bring benefits. Thus, in this study, it was proposed the development of liposomes composed of DOX and TS (pHSL-TS-DOX). A new DOX encapsulation method, without using the classic ammonium sulfate gradient with high encapsulation percentage was developed. Analysis of Small Angle X-ray Scattering (SAXS) and release study proved the pH-sensitivity of the developed formulation. It was observed stabilization of tumor growth using pHSL-TS-DOX when compared to free DOX. The toxicity tests showed the safety of this formulation since it allowed body weight initial recovery after the treatment and harmless to heart and liver, main target organs of DOX toxicity. The developed formulation also avoided the occurrence of myelosuppression, a typical adverse effect of DOX. Therefore, pHSL-TS-DOX is a promising alternative for the treatment of breast cancer since it has adequate antitumor activity and a safe toxicity profile.

Hydrophobic ion pairing: encapsulating small molecules, peptides, and proteins into nanocarriers

Hydrophobic ion pairing has emerged as a method to modulate the solubility of charged hydrophilic molecules ranging in class from small molecules to large enzymes. Charged hydrophilic molecules are ionically paired with oppositely-charged molecules that include hydrophobic moieties; the resulting uncharged complex is water-insoluble and will precipitate in aqueous media. Here we review one of the most prominent applications of hydrophobic ion pairing: efficient encapsulation of charged hydrophilic molecules into nano-scale delivery vehicles - nanoparticles or nanocarriers. Hydrophobic complexes are formed and then encapsulated using techniques developed for poorly-water-soluble therapeutics. With this approach, researchers have reported encapsulation efficiencies up to 100% and drug loadings up to 30%. This review covers the fundamentals of hydrophobic ion pairing, including nomenclature, drug eligibility for the technique, commonly-used counterions, and drug release of encapsulated ion paired complexes. We then focus on nanoformulation techniques used in concert with hydrophobic ion pairing and note strengths and weaknesses specific to each. The penultimate section bridges hydrophobic ion pairing with the related fields of polyelectrolyte coacervation and polyelectrolyte-surfactant complexation. We then discuss the state of the art and anticipated future challenges. The review ends with comprehensive tables of reported hydrophobic ion pairing and encapsulation from the literature.

Cellular viability and osteogenic differentiation potential of human gingiva-derived stem cells in 2D culture following treatment with anionic, cationic, and neutral liposomes containing doxorubicin

The effects of doxorubicin, particularly doxorubicin liposome, on stem cells have remained to be fully elucidated. The aim of the present study was to evaluate the effects of anionic, cationic and neutral liposomes loaded with doxorubicin on the viability and osteogenic differentiation potential of human gingiva-derived stem cells in two-dimensional culture. Doxorubicin-loaded liposomes were prepared using the traditional thin-lipid-film hydration method. Stem cells were seeded on a culture plate and maintained in osteogenic media. The morphology of the stem cells was observed under an inverted microscope. The number of viable cells was determined using a Cell-Counting Kit-8 assay. The alkaline phosphatase activity was assessed and Alizarin Red S staining was performed to evaluate osteogenic differentiation. A higher concentration of doxorubicin caused noticeable changes in the morphology of the stem cells. Decreases in cellular viability were observed after applying doxorubicin. The application of doxorubicin, particularly at higher concentrations, produced a noticeable decrease in alkaline phosphatase activity and Alizarin Red S staining. The present study indicated that application of doxorubicin with or without liposomes reduced the cellular viability and osteogenic differentiation. Among the different treatments, the doxorubicin-loaded cationic liposomes induced the strongest reduction in the cellular viability and osteogenic differentiation in the stem cell culture.

Vincristine-loaded liposomes prepared by ion-paring techniques: Effect of lipid, pH and antioxidant on chemical stability

In the present study, vincristine (VCR)-loaded liposomes were designed by ion-pairing techniques and the model could be applied to investigate the effect of lipids on the degradation of vinca alkaloids, and how to weaken their influence by adjusting pH and adding antioxidants. It was found that there was a positive correlation between degree of degradation and the unsaturation extent of the phospholipids. In the phospholipid with the lowest oxidation index, only 6% of VCR was degraded in 6days at 37°C, whereas for the phospholipids with highest oxidation index, the degradation reached above 95% over the same time. At pH6.8 and 7.4, the degradation rate of VCR in the lipid membrane was significantly faster than that in aqueous solution, instead, at pH5.0. After the addition of butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tocopherol, ascorbate and tocopherol with ascorbate, the residual content of VCR after 6days was 79.9%, 78.1%, 7.1%, 89.6% and 94.6% respectively. It was speculated that VCR could be oxidized by hydrated peroxyl radicals, which formed from lipid peroxidation as well as nucleophilic substitution with peroxyl radicals in the dry state. Also, the antioxidants were shown to have different eliminating capacity on the peroxyl radicals whether hydrated or not, and the phenoxyl radicals generated from fat-soluble antioxidants may be potentially destabilizing to VCR. Therefore, for these two crucial reasons, the degradation of VCR was quite different when used with a combination of water and fat-soluble antioxidants, and thus provides the best protection for VCR.