Enhanced tumor MR imaging with gadolinium-loaded polychelating polymer-containing tumor-targeted liposomes.

PURPOSE: To significantly enhance tumor MR imaging by using a contrast agent combining three components -- a long-circulating liposome, liposomal membrane-incorporated polychelating amphiphilic polymer heavily loaded with gadolinium, and cancer-specific monoclonal antibody 2C5 attached to the liposome surface. MATERIALS AND METHODS: Tumor-bearing animals were imaged prior and 4, 24, and 48 hours after i.v. injection of 2C5-modified and unmodified Gd-PAP-containing PEGylated liposomes. The faster and more specific accumulation of the novel contrast nanoparticles in tumors was also confirmed by 3D angiograms and by direct visualization of Gd-immunoliposomes in tumor sections by confocal microscopy. RESULTS: 2C5-modified Gd-PAP-containing PEGylated liposomes allowed for fast and specific tumor imaging as early as 4 hours postinjection. T1 inversion recovery maps demonstrated a significant increase in tumor-associated R1 in animals injected with antibody-modified Gd-loaded liposomes 4 hours postinjection, followed by a gradual decrease consistent with clearance of the agent from the tumor region. In control animals injected with antibody-free liposomes the corresponding R1 values at all investigated timepoints were significantly smaller. CONCLUSION: The results support the feasibility of using such multifunctional nanoparticular liposome-based agents simultaneously providing prolonged circulation, heavy Gd load, and specific cancer cell recognition as a superior contrast for MR tumor imaging.

Enhanced in vivo antitumor efficacy of poorly soluble PDT agent, meso-tetraphenylporphine, in PEG-PE-based tumor-targeted immunomicelles.

Poorly soluble photosensitizer, meso-tetraphenylporphine (TPP), was solubilized using the polymeric micelles prepared from polyethylene glycol-phosphatidyl ethanolamine conjugate (PEG-PE). TPP-loaded PEG-PE micelles have been additionally modified with tumor-specific monoclonal 2C5 antibody (mAb 2C5), which resulted in significantly improved anticancer effect of the drug under the PDT conditions against murine Lewis lung carcinoma (LLC) In vivo in female C57BL/6 mice. Fourteen days after tumor inoculation, the mice with more than 2 mm diameter tumors were given an intravenous injection of 1 mg/kg of free TPP or TPP loaded into control PEG-PE micelles or into mAb 2C5-PEG-PE tumor-targeted immunomicelles. Twenty-four hours after the administration, the animals were anesthetized, and tumor sites were illuminated with light (630 nm) for 12 min. Microscopic evaluation of tumor response was conducted in some mice 24 h after light irradiation, and tumor size was followed in the remaining animals for another 35 days. The attachment of mAb 2C5 to TPP-loaded immunomicelles provided the maximum level of tumor growth inhibition. Enhanced tumor accumulation of TPP-loaded mAb 2C5-PEG-PE-immunomicelles was confirmed by gamma-imaging studies. The modification of the TPP-loaded polymeric micelles with tumor-specific antibodies could be used as a general approach to enhance the efficacy of PDT.

Antinucleosome antibody-modified liposomes and lipid-core micelles for tumor-targeted delivery of therapeutic and diagnostic agents.

Liposomes and lipid-core micelles prepared of polyethylene glycol-phosphatidylethanolamine (PEG-PE) conjugates have been modified with nucleosome-specific monoclonal antinuclear autoantibody (ANA) 2C5 (mAb 2C5) specifically recognizing a broad variety of cancer cells through the cancer cell surface-bound nucleosomes. mAb 2C5 preserves its specific properties upon the binding with the lipid-based pharmaceutical nanocarriers, and 2C5-modified immunoliposomes and immunomicelles demonstrate an enhanced binding with tumor cells both in vitro and in vivo. We have investigated the delivery of therapeutic and diagnostic agents with such tumor-targeted immunoliposomes and immunomicelles to various tumors in vivo and in vitro. Both lipid-based nanocarriers provided enhanced tumor delivery of imaging agents ((111)In) and antitumor drugs (doxorubicin and photodynamic therapy agents) to tumor cells under different experimental settings. Pharmaceutical lipid-based nanoparticular carriers modified with mAb 2C5 could represent universal systems for tumor-specific delivery of various soluble and insoluble pharmaceuticals.

Enhanced tumor visualization by gamma-scintigraphy with 111In-labeled polychelating-polymer-containing immunoliposomes.

Here, we have prepared long-circulating PEGylated liposomes heavily loaded with 111In via the liposome-incorporated polylysine-based (PLL-based) polychelating amphiphilic polymer (PAP) and additionally modified with the monoclonal antibody 2C5 (mAb 2C5) possessing the nucleosome-restricted (NS-restricted) specificity and capable of specific recognition of a broad variety of live cancer cells via the cancer cell surface bound NSs. These liposomes have been tested as a tumor-specific contrast agent for the gamma-scintigraphic visualization of model tumors in mice. The tumor accumulation of mAb 2C5 modified liposomes prepared in this study was significantly (3-to-5-fold) higher than in the neighboring muscle tissue at all times after administration (6, 24, and 48 h) in mice bearing murine Lewis lung carcinoma (LLC) and human HT-29 tumors. The whole body direct gamma-imaging of LLC tumor bearing mice at different times has demonstrated the superior in vivo tumor accumulation of the targeted mAb 2C5 modified PAP-containing PEGylated liposomes compared to nontargeted liposomal control formulations, which resulted in better and faster tumor imaging as shown with LLC-bearing mice.

Gadolinium-loaded polychelating polymer-containing cancer cell-specific immunoliposomes.

Liposome loading with Gd via the membrane-incorporated polychelating amphiphilic polymers (PAPs) significantly increases the Gd content and relaxivity (T1 parameter) of PEGylated liposomes, which can be used as contrast agents for magnetic resonance imaging (MRI). Here, we demonstrate that such Gd-containing liposomes can be additionally modified with the monoclonal anticancer antibody 2C5 (mAb 2C5) possessing the nucleosome(NS)-restricted specificity via the PEG spacer. Liposome-bound antibody preserves its specific activity (ELISA) and such Gd-loaded PEGylated 2C5-immunoliposomes specifically recognize various cancer cells in vitro and target an increased amount of Gd to their surface compared to antibody-free Gd-liposomes or Gd-liposomes modified with tumor nonspecific antibody. Gd-loaded cancer cell-targeted immunoliposomes may represent promising agents for enhanced tumor MRI.

Solubilization of poorly soluble PDT agent, meso-tetraphenylporphin, in plain or immunotargeted PEG-PE micelles results in dramatically improved cancer cell killing in vitro.

Poorly soluble photodynamic therapy (PDT) agent, meso-tetratphenylporphine (TPP), was effectively solubilized using non-targeted and tumor-targeted polymeric micelles prepared of polyethylene glycol/phosphatidyl ethanolamine conjugate (PEG-PE). Encapsulation of TPP into PEG-PE-based micelles and immunomicelles (bearing an anti-cancer monoclonal 2C5 antibody) resulted in significantly improved anticancer effects of the drug at PDT conditions against murine (LLC, B16) and human (MCF-7, BT20) cancer cells in vitro. For this purpose, the cells were incubated for 6 or 18 h with the TPP or TPP-loaded PEG-PE micelles/immunomicelles and then light-irradiated for 30 min. The phototoxic effect depended on the TPP concentration and specific targeting by immunomicelles. An increased level of apoptosis was shown in the PDT-treated cultures. The attachment of the anti-cancer 2C5 antibodies to TPP-loaded micelles provided the maximum level of cell killing at a given time. The results of this study showed that TPP-containing PEG-PE micelles may represent a useful formulation of the photosensitizer for practical PDT.