Development of a reproducible procedure for plasmid DNA encapsulation by red blood cell ghosts

Erythrocyte Ghost Based Fusogenic Glycoprotein Vesicular Stomatitis Virus Glycoprotein Complexes as an Efficient Deoxyribonucleic Acid Delivery System

This study aimed to construct a new type of fused erythrocyte vector for gene delivery system. The conditioned medium of AD293 cells expressing vesicular stomatitis virus glycoprotein gene was collected, and erythrocyte ghost was prepared by hypotonic lysis. Using cationic polymer to condense deoxyribonucleic acid to form a complex, fusogenic erythrocyte ghost was incubated with this complex to obtain virion. Flow cytometry and luciferase activity analysis were used to detect the delivery of fusogenic erythrocyte ghost to deoxyribonucleic acid in AD293 cells and refractory cells, respectively. Transfection efficiency of fusogenic erythrocyte ghost in vivo was detected by confocal microscope. Vesicular stomatitis virus glycoprotein and erythrocyte ghost were effectively integrated, and fusogenic erythrocyte ghost was successfully prepared. deoxyribonucleic acid/polyethylenimine complexes form 100–300 nm particles. Fusogenic erythrocyte ghost can effectively incorporation deoxyribonucleic acid complexes. Confocal microscope observed red fluorescence close to blue fluorescence, indicating that labeled fusogenic erythrocyte ghost may trigger liver and spleen tissue endocytosis or fusion. A new delivery vector of fusogenic erythrocyte ghost was constructed. This system could enhance the delivery efficiency even in cells which refractory to conventional transfections in vitro.

Nucleic Acid Delivery with Red-Blood-Cell-Based Carriers

Gene therapy has the potential to become a staple of 21st-century medicine. However, to overcome the limitations of existing gene-delivery therapies, that is, poor stability and inefficient and delivery and accumulation of nucleic acids (NAs), safe drug-delivery systems (DDSs) allowing the prolonged circulation and expression of the administered genes in vivo are needed. In this review article, the development of DDSs over the past 70 years is briefly described. Since synthetic DDSs can be recognized and eliminated as foreign substances by the immune system, new approaches must be found. Using the body's own cells as DDSs is a unique and exciting strategy and can be used in a completely new way to overcome the critical limitations of existing drug-delivery approaches. Among the different circulatory cells, red blood cells (RBCs) are the most abundant and thus can be isolated in sufficiently large quantities to decrease the complexity and cost of the treatment compared to other cell-based carriers. Therefore, in the second part, this article describes 70 years of research on the development of RBCs as DDSs, covering the most important RBC properties and loading methods. In the third part, it focuses on RBCs as the NA delivery system with advantages and drawbacks discussed to decide whether they are suitable for NA delivery in vivo.

Erythrocytes as Carriers: From Drug Delivery to Biosensors

Drug delivery using natural biological carriers, especially erythrocytes, is a rapidly developing field. Such erythrocytes can act as carriers that prolong the drug's action due to its gradual release from the carrier; as bioreactors with encapsulated enzymes performing the necessary reactions, while remaining inaccessible to the immune system and plasma proteases; or as a tool for targeted drug delivery to target organs, primarily to cells of the reticuloendothelial system, liver and spleen. To date, erythrocytes have been studied as carriers for a wide range of drugs, such as enzymes, antibiotics, anti-inflammatory, antiviral drugs, etc., and for diagnostic purposes (e.g. magnetic resonance imaging). The review focuses only on drugs loaded inside erythrocytes, defines the main lines of research for erythrocytes with bioactive substances, as well as the advantages and limitations of their application. Particular attention is paid to in vivo studies, opening-up the potential for the clinical use of drugs encapsulated into erythrocytes.

Incorporation of Viral Glycoprotein VSV-G Improves the Delivery of DNA by Erythrocyte Ghost into Cells Refractory to Conventional Transfection

The objective of this study was to formulate a novel gene delivery system based on the erythrocyte ghost (EG) integrated with fusogenic viral glycoprotein vesicular stomatitis virus glycoprotein G (VSV-G). VSV-G proteins were harvested as condition medium of Ad293 cells carrying a VSV-G transgene and then incorporated into EG. Plasmid DNA was condensed by various transfection reagents. A luciferase expression construct (pGL3-control) and a DsRed expression cassette (pCMV-DsRed) were used to evaluate the delivery efficiency of DNA/EG/VSV-G complexes. VSV-G proteins could be incorporated into EG in static incubation under acidic conditions as evidenced by the Western blot analysis. Condensed plasmid DNA was bound mostly to the outer surface of EG, which could be detected by electromicroscopy and measured by electrophoresis. EG/VSV-G complexes stimulated the delivery of pGL3-control into Ad293 cells significantly with the luciferase activity increased about 4-fold as compared to that of the control. The delivery of pCMV-DsRed was also enhanced with the percentage of DsRed-positive Ad293 cells increased from 55 % to about 80 %. Moreover, the transfection efficiency in 3T3, HeLa, INS-1, and bone marrow stem cell (BMSC) cells increased about 2-3-fold. Finally, confocal microscopy analysis showed that incorporation of VSV-G significantly enhanced the endocytosis of EG into target cells. In the present study, a novel type of non-viral DNA delivery vehicle consisting of EG and fusogenic VSV-G proteins was formulated, which showed superior transfection efficiency even in cells resistant to classical transfection.

The effect of a peptide-containing synthetic lung surfactant on gas exchange and lung mechanics in a rabbit model of surfactant depletion

Background

Currently, a new generation of synthetic pulmonary surfactants is being developed that may eventually replace animal-derived surfactants used in the treatment of respiratory distress syndrome. Enlightened by this, we prepared a synthetic peptide-containing surfactant (Synsurf) consisting of phospholipids and poly-l-lysine electrostatically bonded to poly-l-glutamic acid. Our objective in this study was to investigate if bronchoalveolar lavage (BAL)-induced acute lung injury and surfactant deficiency with accompanying hypoxemia and increased alveolar and physiological dead space is restored to its prelavage condition by surfactant replacement with Synsurf, a generic prepared Exosurf, and a generic Exosurf containing Ca²⁺.

Methods

Twelve adult New Zealand white rabbits receiving conventional mechanical ventilation underwent repeated BAL to create acute lung injury and surfactant-deficient lung disease. Synthetic surfactants were then administered and their effects assessed at specified time points over 5 hours. The variables assessed before and after lavage and surfactant treatment included alveolar and physiological dead space, dead space/tidal volume ratio, arterial end-tidal carbon dioxide tension (PCO₂) difference (mainstream capnography), arterial blood gas analysis, calculated shunt, and oxygen ratios.

Results

BAL led to acute lung injury characterized by an increasing arterial PCO₂ and a simultaneous increase of alveolar and physiological dead space/tidal volume ratio with no intergroup differences. Arterial end-tidal PCO₂ and dead space/tidal volume ratio correlated in the Synsurf, generic Exosurf and generic Exosurf containing Ca²⁺ groups. A significant and sustained improvement in systemic oxygenation occurred from time point 180 minutes onward in animals treated with Synsurf compared to the other two groups (P < 0.001). A statistically significant decrease in pulmonary shunt (P < 0.001) was found for the Synsurf-treated group of animals, as well as radiographic improvement in three out of four animals in that group.

Conclusion

In general, surfactant-replacement therapy in the animals did not fully restore the lung to its prelavage condition. However, our data show that the formulated surfactant Synsurf improves oxygenation by lowering pulmonary shunt.

PTD-mediated loading of tumor-seeking lymphocytes with prodrug-activating enzymes

Using the approach of peptide transduction domain (PTD)-mediated loading of interleukin-2(IL-2)-activated natural killer (A-NK) cells, tumor-seeking lymphocytes, with prodrug-activating enzymes, we primarily aim to generate a cytotoxic drug selectively within tumors and minimize damage to normal tissues. A-NK cells are able to accumulate selectively at tumor sites. While these cells by themselves possess significant antitumor effect in vivo, we suggest that they can also serve as Trojan horses, by bringing anticancer agents, such as prodrug-activating enzymes, selectively to tumors. We have successfully demonstrated in a mouse model that A-NK cells can be rapidly loaded with prodrug-activating enzymes, such as alkaline phosphatase (AP) and beta-galactosidase (beta-gal), in vitro using enzyme-conjugated peptide PTD5. Upon adoptive transfer into lung-tumor-bearing animals, the loaded A-NK cells are able to bring their cargo of the prodrug-activating enzymes selectively to pulmonary metastases. The targeting of the AP to the tumor tissues is highly specific, since more than a fivefold higher concentration of AP was found in the tumor tissues compared to the surrounding normal lung tissue at 24 h after injection. The approach of transporting prodrug-activating enzymes selectively into tumors clearly shows potential for future targeted chemotherapy. Ongoing studies in our laboratory are evaluating the antitumor efficacy of cellular-dependent enzyme prodrug therapy.

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.