Delivery to macrophages and toxic action of etoposide carried in mouse red blood cells

Hybrid liposome-erythrocyte drug delivery system for tumor therapy with enhanced targeting and blood circulation

Liposome, a widely used drug delivery system (DDS), still shows several disadvantages such as dominant clearance by liver and poor target organ deposition. To overcome the drawbacks of liposomes, we developed a novel red blood cell (RBC)-liposome combined DDS to modulate the tumor accumulation and extend the blood circulation life of the existing liposomal DDS. Here, RBCs, an ideal natural carrier DDS, were utilized to carry liposomes and avoid them undergo the fast clearance in the blood. In this study, liposomes could either absorbed onto RBCs' surface or fuse with RBCs' membrane by merely altering the interaction time at 37°C, while the interaction between liposome and RBCs would not affect RBCs' characteristics. In the in vivo antitumor therapeutic efficacy study, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes attached onto RBCs' surfaces exhibited lung targeting effect (via RBC-hitchhiking approach) and reduced clearance in the liver, while DPPC liposomes fused with RBCs had prolong blood circulation up to 48 h and no enrichment in any organ. Furthermore, 20 mol% of DPPC liposomes were replaced with pH-sensitive phospholipid 1,2-dioleoyl-Sn-glycero-3-phosphoethanolamine (DOPE) as it could respond to the low pH tumor microenvironment and then accumulate in the tumor. The DOPE attached/fusion RBCs showed partial enrichment in lung and about 5-8% tumor accumulation, which were significantly higher than (about 0.7%) the conventional liposomal DDS. Thus, RBC-liposome composite DDS is able to improve the liposomal tumor accumulation and blood circulation and shows the clinical application promises of using autologous RBCs for antitumor therapy.

Biological and Intracellular Fates of Drug Nanocrystals through Different Delivery Routes: Recent Development Enabled by Bioimaging and PK Modeling

Nanocrystals have contributed to exciting improvements in the delivery of poorly water-soluble drugs. The biological and intracellular fates of nanocrystals are currently under debate. Due to the remarkable commercial success in enhancing oral bioavailability, nanocrystals have originally been regarded as a simple formulation approach to enhance dissolution. However, the latest findings from novel bioimaging tools lead to an expanded view. Intact nanocrystals may offer long-term durability in the body and offer drug delivery capabilities like those of other nano-carriers. This review renews the understanding of the biological fates of nanocrystals administered via oral, intravenous, and parenteral (e.g., dermal, ocular, and pulmonary) routes. The intracellular pathways and dissolution kinetics of nanocrystals are explored. Additionally, the future trends for in vitro and in vivo quantification of nanocrystals, as well as factors impacting the biological and intracellular fates of nanocrystals are discussed. In conclusion, nanocrystals present a promising and underexplored therapeutic opportunity with immense potential.

A Review of Controlled Drug Delivery Systems Based on Cells and Cell Membranes

Novel drug delivery systems have ameliorated drugs’ pharmacokinetics and declined undesired ramifications while led to a better patient compliance by extending the time of release. In fact, although there has been a multitude of encouraging achievements in controlled drug release, the application of micro- and nano-carriers is confronted with some challenges such as rapid clearance and inefficient targeting. In addition, since cell systems can be an appropriate alternative to micro- and nano-particles, they have been used as biological carriers. In general, features such as stable release into blood, slow clearance, efficient targeting, and high biocompatibility are the main properties of cells applied as drug carriers. Furthermore, some cells such as erythrocytes, leukocytes, stem cells, and platelets have been used as release systems. Hence, most common cells that were used as aforementioned release systems are going to be presented in this review article.

Recent advancements in erythrocytes, platelets, and albumin as delivery systems

In the past few years, nanomaterial-based drug delivery systems have been applied to enhance the efficacy of therapeutics and to alleviate negative effects through the controlled delivery of targeting and releasing agents. However, few drug carriers can achieve high targeting efficacy, even when targeting modalities and surface markers are introduced. Immunological problems have also limited their wide applications. Biological drug delivery systems, such as erythrocytes, platelets, and albumin, have been extensively investigated because of their unique properties. In this review, erythrocytes, platelets, and albumin are described as efficient drug delivery systems. Their properties, applications, advantages, and limitations in disease treatment are explained. This review confirms that these systems can be used to facilitate a specific, biocompatible, and smart drug delivery.

Co-opting biology to deliver drugs

The goal of drug delivery is to improve the safety and therapeutic efficacy of drugs. This review focuses on delivery platforms that are either derived from endogenous pathways, long-circulating biomolecules and cells or that piggyback onto long-circulating biomolecules and cells. The first class of such platforms is protein-based delivery systems--albumin, transferrin, and fusion to the Fc domain of antibodies--that have a long-circulation half-life and are designed to transport different molecules. The second class is lipid-based delivery systems-lipoproteins and exosomes-that are naturally occurring circulating lipid particles. The third class is cell-based delivery systems--erythrocytes, macrophages, and platelets--that have evolved, for reasons central to their function, to exhibit a long life-time in the body. The last class is small molecule-based delivery systems that include folic acid. This article reviews the biology of these systems, their application in drug delivery, and the promises and limitations of these endogenous systems for drug delivery.

Drug-loaded sickle cells programmed ex vivo for delayed hemolysis target hypoxic tumor microvessels and augment tumor drug delivery

Selective drug delivery to hypoxic tumor niches remains a significant therapeutic challenge that calls for new conceptual approaches. Sickle red blood cells (SSRBCs) have shown an ability to target such hypoxic niches and induce tumoricidal effects when used together with exogenous pro-oxidants. Here we determine whether the delivery of a model therapeutic encapsulated in murine SSRBCs can be enhanced by ex vivo photosensitization under conditions that delay autohemolysis to a time that coincides with maximal localization of SSRBCs in a hypoxic tumor. Hyperspectral imaging of 4T1 carcinomas shows oxygen saturation levels <10% in a large fraction (commonly 50% or more) of the tumor. Using video microscopy of dorsal skin window chambers implanted with 4T1 tumors, we demonstrate that allogeneic SSRBCs, but not normal RBCs (nRBCs), selectively accumulate in hypoxic 4T1 tumors between 12 and 24h after systemic administration. We further show that ex vivo photo-oxidation can program SSRBCs to postpone hemolysis/release of a model therapeutic to a point that coincides with their maximum sequestration in hypoxic tumor microvessels. Under these conditions, drug-loaded photosensitized SSRBCs show a 3-4 fold greater drug delivery to tumors compared to non-photosensitized SSRBCs, drug-loaded photosensitized nRBCs, and free drug. These results demonstrate that photo-oxidized SSRBCs, but not photo-oxidized nRBCs, sequester and hemolyze in hypoxic tumors and release substantially more drug than photo-oxidized nRBCs and non-photo-oxidized SSRBCs. Photo-oxidation of drug-loaded SSRBCs thus appears to exploit the unique tumor targeting and carrier properties of SSRBCs to optimize drug delivery to hypoxic tumors. Such programmed and drug-loaded SSRBCs therefore represent a novel and useful tool for augmenting drug delivery to hypoxic solid tumors.

Erythrocyte-inspired delivery systems

Herein recent progress in developing red blood cell (RBC)-inspired delivery systems is reviewed, with an emphasis on how our growing understanding of fundamental biological properties of natural RBCs has been applied in the design and engineering of these delivery systems. Specifically, progress achieved in developing carrier RBCs, a class of delivery vehicles engineered by directly loading natural RBCs with therapeutic agents, will be reviewed. Then alternative approaches to engineering synthetic vehicles through mimicking the mechanobiological and chemico-biological properties of natural RBCs will be considered. The synthesis and application of RBC membrane-derived vesicles, of which the natural RBC membranes are collected and directly utilized to prepare drug carriers, will then be discussed. Finally, a recent approach in engineering RBC membrane-camouflaged nanoparticle systems that combine advantages of natural RBCs and synthetic biomaterials will be highlighted. These developments indicate that RBC-inspired delivery systems will result in next-generation nanomedicine with extensive medical applications.

Cell-based drug-delivery platforms

Cell systems have recently emerged as biological drug carriers, as an interesting alternative to other systems such as micro- and nano-particles. Different cells, such as carrier erythrocytes, bacterial ghosts and genetically engineered stem and dendritic cells have been used. They provide sustained release and specific delivery of drugs, enzymatic systems and genetic material to certain organs and tissues. Cell systems have potential applications for the treatment of cancer, HIV, intracellular infections, cardiovascular diseases, Parkinson’s disease or in gene therapy. Carrier erythrocytes containing enzymes such us L-asparaginase, or drugs such as corticosteroids have been successfully used in humans. Bacterial ghosts have been widely used in the field of vaccines and also with drugs such as doxorubicin. Genetically engineered stem cells have been tested for cancer treatment and dendritic cells for immunotherapeutic vaccines. Although further research and more clinical trials are necessary, cell-based platforms are a promising strategy for drug delivery.

Preparation and in-vitro characterization of tramadol-loaded carrier erythrocytes for long-term intravenous delivery

Objectives

The hypo-osmotic dialysis method was used for preparation of tramadol-loaded human intact erythrocytes. In response to rapid drug escape from the erythrocytes, a membrane cross-linker, glutaraldehyde, was used successfully.

Methods

The resulting carrier cells were validated in terms of the accuracy and precision of the whole drug loading procedure.

Key findings

The average loaded amount, entrapment efficiency and cell recovery were 1.9041 mg, 95.98% and 85.13%, respectively. The effects of different drug concentrations on loading parameters were studied with the concentration of 10 mg/ml selected as optimal. A series of in-vitro characteristics of carrier erythrocytes, including tramadol release behaviour, haematological indices, particle size distribution, scanning electron microscopy, and osmotic/turbulence fragilities were determined compared with the sham-entrapped and unloaded cells. The results of these in-vitro tests indicated that the erythrocytes did not undergo remarkable irreversible size and shape/topology changes, but the fragility of the membranes of the processed cells were increased.

Conclusions

The collective results of this study showed that the optimized method of entrapment was suitable for the encapsulation of tramadol in erythrocytes with the final carrier cells ready to enter the in-vivo animal studies as a promising long-circulating carrier for tramadol.

Development of novel 5-fluorouracil carrier erythrocyte with pharmacokinetics and potent antitumor activity in mice bearing malignant ascites

BACKGROUND

To investigate pharmacokinetics and potency of antitumor activity of a novel 5-fluorouracil carrier erythrocyte (RBC-FU) in mice bearing malignant ascites.

METHODS

RBC-FU was synthesized with a hyperosmotic technique. The entrapment efficiency of targeted carrier erythrocytes was determined by reverse dialysis method with high-performance liquid chromatography (HPLC) for analyzing the quantity of 5-fluorouracil (5-FU). After a H22 hepatocarcinoma malignant ascites model was established in Kunming mice, 5-FU encapsulated by carrier erythrocytes (for Group A) and 5-FU solution (for Group B) at 20 mg per kg were injected into the peritoneal cavity of the mice, respectively. Blood and ascites samples were collected at different times to detect 5-FU quantity by HPLC. Body weight and survival time of mice were recorded in Group A, B and the Control Group in which mice were injected with normal saline only.

RESULTS

5-FU was effectively encapsulated into erythrocytes, with an encapsulating effect as 55 +/- 0.50%. In Group A, the maximum concentration (Cmax) and the area under curve (AUC) in peritoneal exudates were significantly higher than those of Group B (P < 0.05). On the other hand, 5-FU level in serum was significantly lower than that in peritoneal exudates of Group A and B (P < 0.05). High drug levels in the abdominal cavity in Group A were maintained longer than those in Group B. Compared with that in Group B and the control, the quantity of malignant ascites in Group A had significant regression and the survival time was prolonged.

CONCLUSION

The hyperosmotic method described here could be suitable for producing this novel RBC-FU as a liposomal drug of potential value for treating malignant ascites by intraperitoneal administration.

Applications of carrier erythrocytes in delivery of biopharmaceuticals

Carrier erythrocytes, resealed erythrocytes loaded by a drug or other therapeutic agents, have been exploited extensively in recent years for both temporally and spatially controlled delivery of a wide variety of drugs and other bioactive agents owing to their remarkable degree of biocompatibility, biodegradability and a series of other potential advantages. Biopharmaceuticals, therapeutically significant peptides and proteins, nucleic acid-based biologicals, antigens and vaccines, are among the recently focused pharmaceuticals for being delivered using carrier erythrocytes. In this article, the potential applications of erythrocytes in drug delivery have been reviewed with a particular stress on the studies and laboratory experiences on successful erythrocyte loading and characterization of the different classes of biopharmaceuticals.

Drug, enzyme and peptide delivery using erythrocytes as carriers

Erythrocytes are potential biocompatible vectors for different bioactive substances, including drugs. These can be used successfully as biological carriers of drugs, enzymes and peptides. There are currently diverse methods that permit drug encapsulation in erythrocytes with an appropriate yield. The methods most commonly employed are based on a high-haematocrit dialysis procedure, mainly hypo-osmotic dialysis. Erythrocytes loaded with drugs and other substances allow for different release rates to be obtained. Encapsulation in erythrocytes significantly changes the pharmacokinetic properties of drugs in both animals and humans, enhancing liver and spleen uptake and targeting the reticulo-endothelial system (RES). Amongst other applications, erythrocytes have been used for drug-targeting the RES with aminoglycoside antibiotics; the selective transport to certain organs and tissues of certain antineoplastic drugs, such as methotrexate, doxorubicine, etoposide, carboplatin, etc.; the encapsulation of angiotensin-converting enzyme (ACE) inhibitors, systemic corticosteroids, the encapsulation of new prodrugs with increased duration of action, etc. Erythrocytes are also attractive systems in the sense of their potential ability to deliver proteins and therapeutic peptides. Thus, erythrocytes have been used for the transport of enzymes destined for the correction of metabolic alterations as l-asparaginase, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (AlDH) among others. Erythrocytes have been used successfully as carriers of anti-HIV peptides, such as AZT, nucleoside analogues, antisense oligonucleotides, antineoplastic peptides, erythropoietin, interleukin 3, etc. Amongst other applications, mention may be made of paramagnetic erythrocytes, encapsulation of MRI contrast agents or the study of the metabolism of the red cell. Although erythrocytes have been applied with different uses in human medicine, their deployment is still very limited due to difficulties involving storage, its exposure to contamination and the absence of a validated industrial procedure for its preparation.