Recent progress of macrophage vesicle-based drug delivery systems

Nanoparticle drug delivery systems (NDDSs) are promising platforms for efficient delivery of drugs. In the past decades, many nanomedicines have received clinical approval and completed translation. With the rapid advance of nanobiotechnology, natural vectors are emerging as novel strategies to carry and delivery nanoparticles and drugs for biomedical applications. Among diverse types of cells, macrophage is of great interest for their essential roles in inflammatory and immune responses. Macrophage-derived vesicles (MVs), including exosomes, microvesicles, and those from reconstructed membranes, may inherit the chemotactic migration ability and high biocompatibility. The unique properties of MVs make them competing candidates as novel drug delivery systems for precision nanomedicine. In this review, the advantages and disadvantages of existing NDDSs and MV-based drug delivery systems (MVDDSs) were compared. Then, we summarized the potential applications of MVDDSs and discuss future perspectives. The development of MVDDS may provide avenues for the treatment of diseases involving an inflammatory process.

Nano-Inspired Technologies for Peptide Delivery

Nano-inspired technologies offer unique opportunities to treat numerous diseases by using therapeutic peptides. Therapeutic peptides have attractive pharmacological profiles and can be manufactured at relatively low costs. The major advantages of using a nanodelivery approach comprises significantly lower required dosages compared to systemic delivery, and thus reduced toxicity and immunogenicity. The combination of therapeutic peptides with delivery peptides and nanoparticles or small molecule drugs offers systemic treatment approaches, instead of aiming for single biological targets or pathways. This review article discusses exemplary state-of-the-art nanosized delivery systems for therapeutic peptides and antibodies, as well as their biochemical and biophysical foundations and emphasizes still remaining challenges. The competition between using different nanoplatforms, such as liposome-, hydrogel-, polymer-, silica nanosphere-, or nanosponge-based delivery systems is still "on" and no clear frontrunner has emerged to date.

Macrophages as delivery vehicles for anticancer agents

The delivery of anticancer agents via passive approaches such as the enhanced permeability and retention effect is unlikely to achieve sufficient concentrations throughout the tumor volume for effective treatment. Cell-based delivery approaches using tumor tropic cells have the potential to overcome the limitations of passive approaches. Specifically, this review focuses on the use of monocytes/macrophages for the delivery of a variety of anticancer agents, including nanoparticles, chemotherapeutics and gene constructs. The efficacy of this delivery approach, both as monotherapy and in combination with light-based phototherapy modalities, has been demonstrated in numerous in vitro and animal studies, however, its clinical potential remains to be determined.

Targeted Delivery to Tumors: Multidirectional Strategies to Improve Treatment Efficiency

Malignant tumors are characterized by structural and molecular peculiarities providing a possibility to directionally deliver antitumor drugs with minimal impact on healthy tissues and reduced side effects. Newly formed blood vessels in malignant lesions exhibit chaotic growth, disordered structure, irregular shape and diameter, protrusions, and blind ends, resulting in immature vasculature; the newly formed lymphatic vessels also have aberrant structure. Structural features of the tumor vasculature determine relatively easy penetration of large molecules as well as nanometer-sized particles through a blood⁻tissue barrier and their accumulation in a tumor tissue. Also, malignant cells have altered molecular profile due to significant changes in tumor cell metabolism at every level from the genome to metabolome. Recently, the tumor interaction with cells of immune system becomes the focus of particular attention, that among others findings resulted in extensive study of cells with preferential tropism to tumor. In this review we summarize the information on the diversity of currently existing approaches to targeted drug delivery to tumor, including (i) passive targeting based on the specific features of tumor vasculature, (ii) active targeting which implies a specific binding of the antitumor agent with its molecular target, and (iii) cell-mediated tumor targeting.

Enhancing the effects of chemotherapy by combined macrophage-mediated photothermal therapy (PTT) and photochemical internalization (PCI)

Light-based treatment modalities such as photothermal therapy (PTT) or photochemical internalization (PCI) have been well documented both experimentally and clinically to enhance the efficacy of chemotherapy. The main purpose of this study was to examine the cytotoxic effects of silica-gold nanoshell (AuNS)-loaded macrophage-mediated (Ma^NS) PTT and bleomycin BLM-PCI on monolayers of squamous cell carcinoma cells. The two modalities were applied separately and in simultaneous combination. Two different wavelengths of light were employed simultaneously, one to activate a highly efficient PCI photosensitizer, AlPcS₂a (670 nm) and the other for the Ma^NS-mediated PTT (810 nm), to evaluate the combined effects of these modalities. The results clearly demonstrated that macrophages could ingest sufficient numbers of silica-gold nanoshells for efficient near infrared (NIR) activated PTT. A significant synergistic effect of simultaneously applied combined PTT and PCI, compared to each modality applied separately, was achieved. Light-driven therapies have the advantage of site specificity, non-invasive and non-toxic application, require inexpensive equipment and can be given as repetitive treatment protocols.

Photothermal Therapy Employing Gold Nanoparticle- Loaded Macrophages as Delivery Vehicles: Comparing the Efficiency of Nanoshells Versus Nanorods

Macrophages (Ma) loaded with gold based nanoparticles, which convert near infrared light to heat, have been studied as targeted transport vectors for photothermal therapy (PTT) of tumors. The purpose of the experiments reported here was to compare the efficacy of gold-silica nanoshells (AuNS) and gold nanorods (AuNR) in macrophage mediated PTT. PTT efficacy was evaluated in hybrid glioma spheroids consisting of human glioma cells and either AuNS or AuNR loaded Ma, designated MaNS and MaNR respectivly. Spheroids were irradiated for 10 min. with light from an 810 nm diode laser at irradiances ranging from 0 to 28 W/cm2. PTT efficacy was determined from spheroid growth over a 14-day period. The uptake by Ma of pegylated AuNR (3.9 ± 0.9 %) was twice that of pegylated AuNS, (7.9 ± 0.7 %). Hybrid spheroids consisting of a 5:1 ratio of glioma cells to loaded Ma exhibited significant growth inhibition with MaNS when subjected to irradiances of 7 W/cm2 or greater. In contrast, no significant growth inhibition was observed for the MaNR hybrid spheroids at this 5:1 ratio, even at the highest irradiance investigated (28 W/cm2). Although AuNR were taken up by Ma in larger numbers then AuNS, MaNS were shown to have greater PTT efficacy compared to MaNR for equivalent numbers of loaded Ma.

Recent advances in cell-mediated nanomaterial delivery systems for photothermal therapy

Cell-mediated “Trojan Horse” delivery vehicles overcome the drug delivery barriers to transport nano-agents enhancing the efficiency of photothermal therapy.

Peptide nanosponges designed for rapid uptake by leukocytes and neural stem cells

The structure of novel binary nanosponges consisting of (cholesterol-(K/D)_nDEVDGC)₃-trimaleimide units possessing a trigonal maleimide linker, to which either lysine (K)₂₀ or aspartic acid (D)₂₀ are tethered, has been elucidated by means of TEM. A high degree of agreement between these findings and structure predictions through explicit solvent and then coarse-grained molecular dynamics (MD) simulations has been found. Based on the nanosponges' structure and dynamics, caspase-6 mediated release of the model drug 5(6)-carboxyfluorescein has been demonstrated. Furthermore, the binary (DK20) nanosponges have been found to be virtually non-toxic in cultures of neural progenitor cells. It is of a special importance for the future development of cell-based therapies that DK20 nanosponges were taken up efficiently by leucocytes (WBC) in peripheral blood within 3 h of exposure. The percentage of live cells among the WBC was not significantly decreased by the DK20 nanosponges. In contrast to stem cell or leucocyte cell cultures, which have to be matched to the patient, autologous cells are optimal for cell-mediated therapy. Therefore, the nanosponges hold great promise for effective cell-based tumor targeting.

Nanosponges for drug delivery.

Photochemical internalization enhanced macrophage delivered chemotherapy

BACKGROUND

Macrophage (Ma) vectorization of chemotherapeutic drugs has the advantage for cancer therapy in that it can actively target and maintain an elevated concentration of drugs at the tumor site, preventing their spread into healthy tissue. A potential drawback is the inability to deliver a sufficient number of drug-loaded Ma into the tumor, thus limiting the amount of active drug delivered. This study examined the ability of photochemical internalization (PCI) to enhance the efficacy of released drug by Ma transport.

METHODS

Tumor spheroids consisting of either F98 rat glioma cells or F98 cells combined with a subpopulation of empty or doxorubicin (DOX)-loaded mouse Ma (RAW264.7) were used as in vitro tumor models. PCI was performed with the photosensitizer AlPcS_2a and laser irradiation at 670 nm.

RESULTS

RAW264.7 Ma pulsed with DOX released the majority of the incorporated DOX within two hours of incubation. PCI significantly increased the toxicity of DOX either as pure drug or derived from monolayers of DOX-loaded Ma. Significant growth inhibition of hybrid spheroids was also observed with PCI even at subpopulations of DOX-loaded Ma as low as 11% of the total initial hybrid spheroid cell number.

CONCLUSION

Results show that RAW264.7 Ma, pulsed with DOX, could effectively incorporate and release DOX. PCI significantly increased the ability of both free and Ma-released DOX to inhibit the growth of tumor spheroids in vitro. The growth of F98 + DOX loaded Ma hybrid spheroids were synergistically reduced by PCI, compared to either photodynamic therapy or released DOX acting alone.

In vitro exploration of a myeloid-derived suppressor cell line as vehicle for cancer gene therapy

Recent research indicates that cell-mediated gene therapy can be an interesting method to obtain intratumoral expression of therapeutic proteins. This paper explores the possibility of using transfected myeloid-derived suppressor cells (MDSCs), derived from a murine cell line, as cellular vehicles for transporting plasmid DNA (pDNA) encoding interleukin-12 (IL-12) to tumors. Transfecting these cells via electroporation caused massive cell death. This was not due to electroporation-induced cell damage, but was mainly the result of the intracellular presence of plasmids. In contrast, pDNA transfection using Lipofectamine 2000 (LF2000) did not result in a significant loss of viability. Differences in delivery mechanism may explain the distinctive effects on cell viability. Indeed, electroporation is expected to cause a rapid and massive influx of pDNA resulting in cytosolic pDNA levels that most likely surpass the activation threshold of the intracellular DNA sensors leading to cell death. In contrast, a more sustained intracellular release of the pDNA is expected with LF2000. After lipofection with LF2000, 56% of the MDSCs were transfected and transgene expression lasted for at least 24 h. Moreover, biologically relevant amounts of IL-12 were produced by the MDSCs after lipofection with an IL-12 encoding pDNA. In addition, IL-12 transfection caused a significant upregulation of CD80 and considerably reduced the immunosuppressive capacity of the MDSCs. IL-12-transfected MDSCs were still able to migrate to tumor cells, albeit that lipofection of the MDSCs seemed to slightly decrease their migration capacity.

Dual targeting and enhanced cytotoxicity to HER2-overexpressing tumors by immunoapoptotin-armored mesenchymal stem cells

Mesenchymal stem cells (MSCs) are promising vehicles for the delivery of anticancer agents in cancer therapy. However, the tumor targeting of loaded therapeutics is essential. Here, we explored a dual-targeting strategy to incorporate tumor-tropic MSC delivery with HER2-specific killing by the immunoapoptotin e23sFv-Fdt-tBid generated in our previous studies. The MSC engineering allowed simultaneous immunoapoptotin secretion and bioluminescence detection of the modified MSCs. Systemic administration of the immunoapoptotin-engineered MSCs was investigated in human HER2-reconstituted syngeneic mouse models of orthotopic and metastatic breast cancer, as well as in a xenograft nude mouse model of orthotopic gastric cancer. In vivo dual tumor targeting was confirmed by local accumulation of the bioluminescence-imaged MSCs and persistence of His-immunostained immunoapoptotins in tumor sites. The added tumor preference of MSC-secreted immunoapoptotins resulted in a significantly stronger antitumor effect compared with purified immunoapoptotins and Jurkat-delivered immunoapoptotins. This immunoapoptotin-armored MSC strategy provides a rationale for its use in extended malignancies by combining MSC mobility with redirected immunoapoptotins against a given tumor antigen.

Cell Mediated Photothermal Therapy of Brain Tumors

Gold based nanoparticles with strong near infra-red (NIR) absorption are ideally suited for photothermal therapy (PTT) of brain tumors. The goal of PTT is to induce rapid heating in tumor tissues while minimizing thermal diffusion to normal brain. PTT efficacy is sensitively dependent on both nanoparticle concentration and distribution in tumor tissues. Nanoparticle delivery via passive approaches such as the enhanced permeability and retention (EPR) effect is unlikely to achieve sufficient nanoparticle concentrations throughout tumor volumes required for effective PTT. A simple approach for improving tumor biodsitribution of nanoparticles is the use of cellular delivery vehicles. Specifically, this review focuses on the use of monocytes/macrophages (Mo/Ma) as gold nanoparticle delivery vectors for PTT of brain tumors. Although the efficacy of this delivery approach has been demonstrated in both in vitro and animal PTT studies, its clinical potential for the treatment of brain tumors remains uncertain.

Photothermal enhancement of chemotherapy mediated by gold-silica nanoshell-loaded macrophages: in vitro squamous cell carcinoma study

Moderate hyperthermia (MHT) has been shown to enhance the effects of chemotherapeutic agents in a wide variety of cancers. The purpose of this study was to investigate the combined effects of commonly used chemotherapeutic agents with MHT induced by near-infrared (NIR) activation of gold nanoshell (AuNS)-loaded macrophages (Ma). AuNS-loaded murine Ma combined with human FaDu squamous cells, in hybrid monolayers, were subjected to three cytotoxic drugs (doxorubicin, bleomycin, cisplatin) with or without NIR laser irradiation. For all three drugs, efficacy was increased by NIR activation of AuNS-loaded Ma. The results of this in vitro study provide proof-of-concept for the use of AuNS-loaded Ma for photothermal enhancement of the effects of chemotherapy on squamous cell carcinoma.

Macrophages as nanoparticle delivery vectors for photothermal therapy of brain tumors

Certain types of stem and immune cells, which have an innate ability to target and infiltrate tumors, can be utilized as vectors to deliver several types of anticancer agents. In particular monocytes have the advantage of carrying relatively large payloads of therapeutic nanomaterials, can be patient derived in large numbers and are able to actively infiltrate tumors despite many barriers often present in the microenvironment. Monocytes can selectively cross the compromised blood-brain barrier surrounding brain tumors and are known to actively migrate to hypoxic tumor regions. Of particular interest is the observation that, following near-infrared exposure of tumors containing gold-nanoshell-loaded macrophages, sufficient hyperthermia can be generated to suppress tumor growth. Collectively, these findings demonstrate the potential of monocytes as nanoparticle delivery vectors for several types of site specific light-based cancer therapies.