Intravital Vascular Phototheranostics and Real-Time Circulation Dynamics of Micro- and Nanosized Erythrocyte-Derived Carriers

Erythrocyte Membrane Camouflaged Nanotheranostics for Optical Molecular Imaging-Escorted Self-Oxygenation Photodynamic Therapy

Hypoxic tumor microenvironment (TME) hampers the application of oxygen (O2)-dependent photodynamic therapy (PDT) in solid tumors. To address this problem, a biomimetic nanotheranostics (named MMCC@EM) is developed for optical molecular imaging-escorted self-oxygenation PDT. MMCC@EM is synthesized by encapsulating chlorin e6 (Ce6) and catalase (CAT) in metal-organic framework (MOF) nanoparticles with erythrocyte membrane (EM) camouflage. Based on the biomimetic properties of EM, MMCC@EM efficiently accumulates in tumor tissues. The enriched MMCC@EM achieves TME-activatable drug release, thereby releasing CAT and Ce6, and this process can be monitored through fluorescence (FL) imaging. In addition, endogenous hydrogen peroxide (H2O2) will be decomposed by CAT to produce O2, which can be reflected by the measurement of intratumoral oxygen concentration using photoacoustic (PA) imaging. Such self-oxygenation nanotheranostics effectively mitigate tumor hypoxia and improve the generation of singlet oxygen (1O2). The 1O2 disrupts mitochondrial function and triggers caspase-3-mediated cellular apoptosis. Furthermore, MMCC@EM triggers immunogenic cell death (ICD) effect, leading to an increased infiltration of cytotoxic T lymphocytes (CTLs) into tumor tissues. As a result, MMCC@EM exhibits good therapeutic effects in 4T1-tumor bearing mice under the navigation of FL/PA duplex imaging.

Membrane cholesterol enrichment and folic acid functionalization lead to increased accumulation of erythrocyte-derived optical nano-constructs within the ovarian intraperitoneal tumor implants in mice

Cytoreductive surgery remains as the gold standard to treat ovarian cancer, but with limited efficacy since not all tumors can be intraoperatively visualized for resection. We have engineered erythrocyte-derived nano-constructs that encapsulate the near infrared (NIR) fluorophore, indocyanine green (ICG), as optical probes for NIR fluorescence imaging of ovarian tumors. Herein, we have enriched the membrane of these nano-constructs with cholesterol, and functionalized their surface with folic acid (FA) to target the folate receptor-α. Using a mouse model, we show that the average fraction of the injected dose per tumor mass for nano-constructs with both membrane cholesterol enrichment and FA functionalization was ~ sixfold higher than non-encapsulated ICG, ~ twofold higher than nano-constructs enriched with cholesterol alone, and 33 % higher than nano-constructs with only FA functionalization at 24-h post-injection. These results suggest that erythrocyte-derived nano-constructs containing both cholesterol and FA present a platform for improved fluorescence imaging of ovarian tumors.

Drug-loaded erythrocytes: Modern approaches for advanced drug delivery for clinical use

Scientific organizations worldwide are striving to create drug delivery systems that provide a high local concentration of a drug in pathological tissue without side effects on healthy organs in the body. Important physiological properties of red blood cells (RBCs), such as frequent renewal ability, good oxygen carrying ability, unique shape and membrane flexibility, allow them to be used as natural carriers of drugs in the body. Erythrocyte carriers derived from autologous blood are even more promising drug delivery systems due to their immunogenic compatibility, safety, natural uniqueness, simple preparation, biodegradability and convenience of use in clinical practice. This review is focused on the achievements in the clinical application of targeted drug delivery systems based on osmotic methods of loading RBCs, with an emphasis on advancements in their industrial production. This article describes the basic methods used for encapsulating drugs into erythrocytes, key strategic approaches to the clinical use of drug-loaded erythrocytes obtained by hypotonic hemolysis. Moreover, clinical trials of erythrocyte carriers for the targeted delivery are discussed. This article explores the recent advancements and engineering approaches employed in the encapsulation of erythrocytes through hypotonic hemolysis methods, as well as the most promising inventions in this field. There is currently a shortage of reviews focused on the automation of drug loading into RBCs; therefore, our work fills this gap. Finally, further prospects for the development of engineering and technological solutions for the automatic production of drug-loaded RBCs were studied. Automated devices have the potential to provide the widespread production of RBC-encapsulated therapeutic drugs and optimize the process of targeted drug delivery in the body. Furthermore, they can expedite the widespread introduction of this innovative treatment method into clinical practice, thereby significantly expanding the effectiveness of treatment in both surgery and all areas of medicine.

Red blood cells: a potential delivery system

Red blood cells (RBCs) are the most abundant cells in the body, possessing unique biological and physical properties. RBCs have demonstrated outstanding potential as delivery vehicles due to their low immunogenicity, long-circulating cycle, and immune characteristics, exhibiting delivery abilities. There have been several developments in understanding the delivery system of RBCs and their derivatives, and they have been applied in various aspects of biomedicine. This article compared the various physiological and physical characteristics of RBCs, analyzed their potential advantages in delivery systems, and summarized their existing practices in biomedicine.

Proteomes of Micro- and Nanosized Carriers Engineered from Red Blood Cells

Red blood cell (RBC)-derived systems offer a potential platform for delivery of biomedical cargos. Although the importance of specific proteins associated with the biodistribution and pharmacokinetics of these particles has been recognized, it remains to be explored whether some of the key transmembrane and cytoskeletal proteins responsible for immune-modulatory effects and mechanical integrity of the particles are retained. Herein, using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and quantitative tandem mass tag mass spectrometry in conjunction with bioinformatics analysis, we have examined the proteomes of micro- and nanosized erythrocyte ghosts doped with indocyanine green and compared them with those of RBCs. We identified a total of 884 proteins in each set of RBCs, micro-, and nanosized particles, of which 8 and 45 proteins were expressed at significantly different relative abundances when comparing micro-sized particles vs RBCs and nanosized particles vs RBCs, respectively. We found greater differences in relative abundances of some mechano-modulatory proteins, such as band 3 and protein 4.2, and immunomodulatory proteins like CD44, CD47, and CD55 in nanosized particles as compared to RBCs. Our findings highlight that the methods utilized in fabricating RBC-based systems can induce substantial effects on their proteomes. Mass spectrometry data are available at ProteomeXchange with the identifier PXD038780.

Erythrocyte-Derived Nanoparticles with Folate Functionalization for Near Infrared Pulsed Laser-Mediated Photo-Chemotherapy of Tumors

Despite its common side effects and varying degrees of therapeutic success, chemotherapy remains the gold standard method for treatment of cancer. Towards developing a new therapeutic approach, we have engineered nanoparticles derived from erythrocytes that contain indocyanine green as a photo-activated agent that enables near infrared photothermal heating, and doxorubicin hydrochloride (DOX) as a chemotherapeutic drug. We hypothesize that milliseconds pulsed laser irradiation results in rapid heating and photo-triggered release of DOX, providing a dual photo-chemo therapeutic mechanism for tumor destruction. Additionally, the surface of the nanoparticles is functionalized with folate to target the folate receptor-α on tumor cells to further enhance the therapeutic efficacy. Using non-contract infrared radiometry and absorption spectroscopy, we have characterized the photothermal response and photostability of the nanoparticles to pulsed laser irradiation. Our in vitro studies show that these nanoparticles can mediate photo-chemo killing of SKOV3 ovarian cancer cells when activated by pulsed laser irradiation. We further demonstrate that this dual photo-chemo therapeutic approach is effective in reducing the volume of tumor implants in mice and elicits an apoptotic response. This treatment modality presents a promising approach in destruction of small tumor nodules.

Recent advances in erythrocyte membrane-camouflaged nanoparticles for the delivery of anti-cancer therapeutics

INTRODUCTION

Red blood cell (or erythrocyte) membrane-camouflaged nanoparticles (RBC-NPs) not only have a superior circulation life and do not induce accelerated blood clearance, but also possess special functions, which offers great potential in cancer therapy.

AREAS COVERED

This review focuses on the recent advances of RBC-NPs for delivering various agents to treat cancers in light of their vital role in improving drug delivery. Meanwhile, the construction and in vivo behavior of RBC-NPs are discussed to provide an in-depth understanding of the basis of RBC-NPs for improved cancer drug delivery.

EXPERT OPINION

Although RBC-NPs are quite prospective in delivering anti-cancer therapeutics, they are still in their infancy stage and many challenges need to be overcome for successful translation into the clinic. The preparation and modification of RBC membranes, the optimization of coating methods, the scale-up production and the quality control of RBC-NPs, and the drug loading and release should be carefully considered in the clinical translation of RBC-NPs for cancer therapy.

Morphological Characteristics, Hemoglobin Content, and Membrane Mechanical Properties of Red Blood Cell Delivery Systems

Red blood cell (RBC)-based systems are under extensive development as platforms for the delivery of various biomedical agents. While the importance of the membrane biochemical characteristics in relation to circulation kinetics of RBC delivery systems has been recognized, the membrane mechanical properties of such carriers have not been extensively studied. Using optical methods in conjunction with image analysis and mechanical modeling, we have quantified the morphological and membrane mechanical characteristics of RBC-derived microparticles containing the near-infrared cargo indocyanine green (ICG). We find that these particles have a significantly lower surface area, volume, and deformability as compared to normal RBCs. The residual hemoglobin has a spatially distorted distribution in the particles. The membrane bending modulus of the particles is about twofold higher as compared to normal RBCs and exhibits greater resistance to flow. The induced increase in the viscous characteristics of the membrane is dominant over the elastic and entropic effects of ICG. Our results suggest that changes to the membrane mechanical properties are a result of impaired membrane-cytoskeleton attachment in these particles. We provide a mechanistic explanation to suggest that the compromised membrane-cytoskeleton attachment and altered membrane compositional and structural asymmetry induce curvature changes to the membrane, resulting in mechanical remodeling of the membrane. These findings highlight the importance of membrane mechanical properties as an important criterion in the design and engineering of future generations of RBC-based delivery systems to achieve prolonged circulation.

Membrane Cholesterol Enrichment of Red Blood Cell-Derived Microparticles Results in Prolonged Circulation

Particles fabricated from red blood cells (RBCs) can serve as vehicles for delivery of various biomedical cargos. Flipping of phosphatidylserine (PS) from the inner to the outer membrane leaflet normally occurs during the fabrication of such particles. PS externalization is a signal for phagocytic removal of the particles from circulation. Herein, we demonstrate that membrane cholesterol enrichment can mitigate the outward display of PS on microparticles engineered from RBCs. Our in-vitro results show that the phagocytic uptake of cholesterol-enriched particles by murine macrophages takes place at a lowered rate, resulting in reduced uptake as compared to RBC-derived particles without cholesterol enrichment. When administered via tail-vein injection into healthy mice, the percent of injected dose (ID) per gram of extracted blood for cholesterol-enriched particles was ∼1.5 and 1.8 times higher than the particles without cholesterol enrichment at 4 and 24 h, respectively. At 24 h, ∼43% ID/g of the particles without cholesterol enrichment was eliminated or metabolized while ∼94% ID/g of the cholesterol-enriched particles were still retained in the body. These results indicate that membrane cholesterol enrichment is an effective method to reduce PS externalization on the surface of RBC-derived particles and increase their longevity in circulation.

Cell Membrane-Cloaked Nanotherapeutics for Targeted Drug Delivery

Cell membrane cloaking technique is bioinspired nanotechnology that takes advantage of naturally derived design cues for surface modification of nanoparticles. Unlike modification with synthetic materials, cell membranes can replicate complex physicochemical properties and biomimetic functions of the parent cell source. This technique indeed has the potential to greatly augment existing nanotherapeutic platforms. Here, we provide a comprehensive overview of engineered cell membrane-based nanotherapeutics for targeted drug delivery and biomedical applications and discuss the challenges and opportunities of cell membrane cloaking techniques for clinical translation.

Cells-Based Drug Delivery for Cancer Applications

The application of cells as carriers to encapsulate chemotherapy drugs is of great significance in antitumor therapy. The advantages of reducing systemic toxicity, enhancing targeting and enhancing the penetrability of drugs to tumor cells make it have great potential for clinical application in the future. Many studies and advances have been made in the encapsulation of drugs by using erythrocytes, white blood cells, platelets, immune cells and even tumor cells. The results showed that the antitumor effect of cell encapsulation chemotherapy drugs was better than that of single chemotherapy drugs. In recent years, the application of cell-based vectors in cancer has become diversified. Both chemotherapeutic drugs and photosensitizers can be encapsulated, so as to achieve multiple antitumor effects of chemotherapy, photothermal therapy and photodynamic therapy. A variety of ways of coordinated treatment can produce ideal results even in the face of multidrug-resistant and metastatic tumors. However, it is regrettable that this technology is only used in vitro for the time being. Standard answers have not yet been obtained for the preservation of drug-loaded cells and the safe way of infusion into human body. Therefore, the successful application of drug delivery technology in clinical still faces many challenges in the future. In this paper, we discuss the latest development of different cell-derived drug delivery systems and the challenges it will face in the future.

Near Infrared Fluorescence Imaging of Intraperitoneal Ovarian Tumors in Mice Using Erythrocyte-Derived Optical Nanoparticles and Spatially-Modulated Illumination

Simple Summary

Ovarian cancer has a greater mortality rate than all gynecological malignancies combined. While cytoreductive surgery remains the primary therapeutic approach, its success is limited by the inability to visualize all tumor nodules for resection. We developed light activated nano-sized particles derived from red blood cells as potential imaging probes for near infrared fluorescence imaging of tumors during cytoreductive surgery. We present the first demonstration of the use of these nanoparticles in conjunction a spatially-modulated illumination (SMI) modality to image ovarian intraperitoneal tumors in mice. Our findings indicate that, at 24 h post-administration, these nanoparticles accumulated at higher levels in tumors as compared to organs, and that use of SMI enhances the image contrast.

Abstract

Ovarian cancer is the deadliest gynecological cancer. Cytoreductive surgery to remove primary and intraperitoneal tumor deposits remains as the standard therapeutic approach. However, lack of an intraoperative image-guided approach to enable the visualization of all tumors can result in incomplete cytoreduction and recurrence. We engineered nano-sized particles derived from erythrocytes that encapsulate the near infrared (NIR) fluorochrome, indocyanine green, as potential imaging probes for tumor visualization during cytoreductive surgery. Herein, we present the first demonstration of the use of these nanoparticles in conjunction with spatially-modulated illumination (SMI), at spatial frequencies in the range of 0–0.5 mm⁻¹, to fluorescently image intraperitoneal ovarian tumors in mice. Results of our animal studies suggest that the nanoparticles accumulated at higher levels within tumors 24 h post-intraperitoneal injection as compared to various other organs. We demonstrate that, under the imaging specifications reported here, use of these nanoparticles in conjunction with SMI enhances the fluorescence image contrast between intraperitoneal tumors and liver, and between intraperitoneal tumors and spleen by nearly 2.1, and 3.0 times, respectively, at the spatial frequency of 0.2 mm⁻¹ as compared to the contrast values at spatially-uniform (non-modulated) illumination. These results suggest that the combination of erythrocyte-derived NIR nanoparticles and structured illumination provides a promising approach for intraoperative fluorescence imaging of ovarian tumor nodules at enhanced contrast.

Phototheranostics Using Erythrocyte-Based Particles

There has been a recent increase in the development of delivery systems based on red blood cells (RBCs) for light-mediated imaging and therapeutic applications. These constructs are able to take advantage of the immune evasion properties of the RBC, while the addition of an optical cargo allows the particles to be activated by light for a number of promising applications. Here, we review some of the common fabrication methods to engineer these constructs. We also present some of the current light-based applications with potential for clinical translation, and offer some insight into future directions in this exciting field.

Biomimetic Nanoscale Erythrocyte Delivery System for Enhancing Chemotherapy via Overcoming Biological Barriers

Overcoming multiple biological barriers, including circulation time in vivo, tumor vascular endothelium, reticuloendothelial system (RES), extracellular matrix (ECM), etc., is the key to improve the therapeutic efficacy of drug delivery systems in treating tumors. Inspired by the ability of natural erythrocytes to cross multiple barriers, in this study, a biomimetic delivery system named NE@DOX-Ang2 was developed for enhancing the chemotherapy of breast cancer, which employed nano-erythrocyte (NE) encapsulating doxorubicin (DOX) and surface modification with a targeted angiopep-2 peptide (Ang2). NE@DOX-Ang2 enhanced the capacity to cross biological barriers in a three-dimensional (3D) tumor spheroid model and in vivo in mice. Compared with a conventional drug delivery system of liposomes, the half-life of NE@DOX-Ang2 increased approximately 2.5 times. Moreover, NE@DOX-Ang2 exhibited excellent tumor-targeting ability and antitumor effects in vitro and in vivo. Briefly, the prepared nano-erythrocyte drug carrier has features of favorable biocompatibility and low immunogenicity and the advantage of prolonging the half-life of drugs, which may provide a novel perspective for development of clinically available nanomedicines.

Dual loading of Nigella sativa oil-atorvastatin in chitosan-carboxymethyl cellulose nanogel as a transdermal delivery system

Both Nigella sativa oil and atorvastatin possess anti-inflammatory, immunomodulatory, antioxidant, and antibacterial properties that benefit wound healing. In this work, chitosan-carboxymethyl cellulose was loaded on N. sativa oil to synthesize oil nanogel (ONG) which was later used to load with atorvastatin to obtain atorvastatin-oil nanogel (ATONG). Evaluation of the particle size of ONG and ATONG proved the average of 172 and 193 nm, and their surface charges were found to be 32.2 and 34.7 mV, respectively. Transmission electron microscopy of the sample showed that the particles had homogeneous size distributions with spherical structures. Moreover, drug loading efficiency, drug release, and stability of ATONG were investigated, and their results confirmed the appropriate loading and release of atorvastatin. Cytotoxicity evaluation demonstrated that ATONG can safely release atorvastatin intracellularly in fibroblasts. Results from in vitro skin permeation of ONG and ATONG also revealed that the nanogels (NGs) has proper flux through the skin layers. The in vitro wound closure assay for ATONG verified the proliferation and migration capabilities of fibroblasts, confirming the positive effect on wound-healing applications. In scratch model of fibroblasts, the treatment with ATONG resulted in an increase in the expression of the FGF2, TGF-β1, and VEGF genes involved in fibroblast proliferation and migration aimed at wound healing (p < .001). ATONG, also demonstrated bactericidal effects against Staphylococcus, S. aureus, and S. epidermidis species. Based on the results, ONG and ATONG exhibited great potential to be used as a transdermal drug carrier and skin wound healing NG, respectively.

Advances on erythrocyte-mimicking nanovehicles to overcome barriers in biological microenvironments

Although nanocarriers offer many advantages as drug delivery systems, their poor stability in circulation, premature drug release and nonspecific uptake in non-target organs have prompted biomimetic approaches using natural cell membranes to camouflage nanovehicles. Among them, erythrocytes, representing the most abundant blood circulating cells, have been extensively investigated for biomimetic coating on artificial nanocarriers due to their upgraded biocompatibility, biodegradability, non-immunogenicity and long-term blood circulation. Due to the cell surface mimetic properties combined with customized core material, erythrocyte-mimicking nanovehicles (EM-NVs) have a wide variety of applications, including drug delivery, imaging, phototherapy, immunomodulation, sensing and detection, that foresee a huge potential for therapeutic and diagnostic applications in several diseases. In this review, we summarize the recent advances in the biomedical applications of EM-NVs in cancer, infection, heart-, autoimmune- and CNS-related disorders and discuss the major challenges and opportunities in this research area.

Acute Immune Response of Micro- and Nanosized Erythrocyte-Derived Optical Particles in Healthy Mice

Erythrocyte-derived particles activated by near-infrared (NIR) light present a platform for various phototheranostic applications. We have engineered such a platform with indocyanine green as the NIR-activated agent. A particular feature of these particles is that their diameters can be tuned from micro- to nanoscale, providing a potential capability for broad clinical utility ranging from vascular to cancer-related applications. An important issue related to clinical translation of these particles is their immunogenic effects. Herein, we have evaluated the early-induced innate immune response of these particles in healthy Swiss Webster mice following tail vein injection by measurements of specific cytokines in blood serum, the liver, and the spleen following euthanasia. In particular, we have investigated the effects of particle size and relative dose, time-dependent cytokine response for up to 6 h postinjection, functionalization of the nanosized particles with folate or Herceptin, and dual injections of the particles 1 week apart. Mean concentrations of interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-α, and monocyte chemoattractant protein (MCP)-1 in response to injection of microsized particles at the investigated relative doses were significantly lower than the corresponding mean concentrations induced by lipopolysaccharide (positive control) at 2 h. All investigated doses of the nanosized particles induced significantly higher concentrations of MCP-1 in the liver and the spleen as compared to phosphate buffer saline (PBS) (negative control) at 2 h. In response to micro- and nanosized particles at the highest investigated dose, there were significantly higher levels of TNF-α in blood serum at 2 and 6 h postinjection as compared to the levels associated with PBS treatment at these times. Whereas the mean concentration of TNF-α in the liver significantly increased between 2 and 6 h postinjection in response to the injection of the microsized particles, it was significantly reduced during this time interval in response to the injection of the nanosized particles. In general, functionalization of the nanosized particles was associated with a reduction of IL-6 and MCP-1 in blood serum, the liver, and the spleen, and TNF-α in blood serum. With the exception of IL-10 in the spleen in response to nanosized particles, the second injection of micro- or nanosized particles did not lead to significantly higher concentrations of other cytokines at the investigated dose as compared to a single injection.

RBC-Derived Optical Nanoparticles Remain Stable After a Freeze-Thaw Cycle

Nanosized carriers engineered from red blood cells (RBCs) provide a means for delivering various cargos, including drugs, biologics, and imaging agents. We have engineered nanosized particles from RBCs, doped with the near-infrared (NIR) fluorochrome, indocyanine green (ICG). An important issue related to clinical translation of RBC-derived nanocarriers, including these NIR nanoparticles, is their stability postfabrication. Freezing may provide a method for long-term storage of these and other RBC-derived nanoparticles. Herein, we have investigated the physical and optical stability of these particles in response to a single freeze-thaw cycle. Nanoparticles were frozen to -20 °C, stored frozen for up to 8 weeks, and then thawed at room temperature. Our results show that the hydrodynamic diameter, zeta potential, optical density, and NIR fluorescence emission of these nanoparticles are retained following the freeze-thaw cycle. The ability of these nanoparticles in NIR fluorescence imaging of ovarian cancer cells, as well as their biodistribution in reticuloendothelial organs of healthy Swiss Webster mice after the freeze-thaw cycle is similar to that for freshly prepared nanoparticles. These results indicate that a single cycle of freezing the RBC-derived nanoparticles to -20 °C followed by thawing at room temperature is an effective method to retain the physical and optical characteristics of the nanoparticles, and their interactions with biological systems without the need for use of cryoprotectants.