Transfecting neurons and glia in the rat using pH-sensitive immunoliposomes

Liposome-Mediated Gene Transfer into Established CNS Cell Lines, Primary Glial Cells, and in Vivo

Sufficient gene transfer into CNS-derived cells is the most crucial step to develop strategies for gene therapy. In this study liposome-mediated gene transfer using a β-galactosidase (β-GAL) reporter gene was performed in vitro (C6 glioma cells, NT2 neuronal precursor cells, 3T3 fibroblasts, primary glial cells) and in vivo. Using Trypan blue exclusion staining, optimal lipid concentration was observed in the range of 10-12 μg/mL. Under optimal conditions (80,000 cells/16 mm well, incubation overnight, lipid/DNA ratio = 1:18) a high transfection rate was achieved (<9% for C6 cells; <1% for NT2 cells). In primary cultures of glial cells a fair amount of positive stained cells (glial cell) was found, but the transfection efficiency was lower (<0.1%). A “boost-lipofection” markedly increased (twice) lipofection efficiency in C6 cells. Expression of β-GAL reached a maximum after 3-5 days. When the liposome–DNA complexes were injected/infused directly into the brains of adult rats, several weakly stained cells could be observed in the brain region adjacent to the injection site. It is concluded that liposome-mediated gene transfer is an efficient method for gene transfer into CNS cells in vitro, but the transfection efficiency into the rat brain in vivo is far too low and therefore not applicable.

Anticancer activity of stoppin based on a novel peptide delivery system

Stoppin (L1) is a newly identified anticancer peptide, which is a potent p53‑MDM2/MDMX inhibitor. Due to its limitation in cell delivery efficiency, a new peptide delivery system was developed based on a nucleic acid‑polypeptide‑liposome complex and its stability and effectiveness in vitro was investigated. The nucleic acid‑stoppin‑liposome complex was prepared and characterization of the complex was conducted. The stability of the complex was evaluated by enzyme digestion. Following transfection of the A549 cells with the complex, detection of green fluorescent protein (GFP) and luciferase activity was conducted to evaluate transfection efficiency. In addition, the anticancer activity of the complex was determined by 3‑(4,5‑dimethyl‑thiazolyl‑2)‑2,5 diphenyltetrazolium bromide assay and apoptosis was detected by flow cytometry. The results indicated that the particle size of the complex was 102±10 nm and the encapsulation rate was ~100% when the ratio of liposome, L1 and plasmid was: 4 µl:1 µg:2 µg. The enzyme digestion experiment demonstrated that the complex was resistant to pancreatic and DNA enzyme degradation, indicating that the complex had biological stability. Cell transfection demonstrated that it had a mutual promotion effect on delivery, which could be confirmed by GFP fluorescence and luciferase assay. The cell‑killing efficiency of this novel delivery system was three times higher than with stoppin alone at a low concentration. In conclusion, this novel stoppin peptide delivery system was stable. The nucleic acid‑peptide‑liposome complex can protect the internal component from the degradation of enzymes, promote entry of the peptide into the cells and enhance the anti‑tumor activity of stoppin. Therefore, it is a promising approach for peptide delivery, which can be characterized and visualized using plasmids with GFP or luciferase.

Multifunctional, stimuli-sensitive nanoparticulate systems for drug delivery

The use of nanoparticulate pharmaceutical drug delivery systems (NDDSs) to enhance the in vivo effectiveness of drugs is now well established. The development of multifunctional and stimulus-sensitive NDDSs is an active area of current research. Such NDDSs can have long circulation times, target the site of the disease and enhance the intracellular delivery of a drug. This type of NDDS can also respond to local stimuli that are characteristic of the pathological site by, for example, releasing an entrapped drug or shedding a protective coating, thus facilitating the interaction between drug-loaded nanocarriers and target cells or tissues. In addition, imaging contrast moieties can be attached to these carriers to track their real-time biodistribution and accumulation in target cells or tissues. Here, I highlight recent developments with multifunctional and stimuli-sensitive NDDSs and their therapeutic potential for diseases including cancer, cardiovascular diseases and infectious diseases.

Plasmid releasing multiple channel bridges for transgene expression after spinal cord injury

The regeneration of tissues with complex architectures requires strategies that promote the appropriate cellular processes, and can direct their organization. Plasmid-loaded multiple channel bridges were engineered for spinal cord regeneration with the ability to support and direct cellular processes and promote gene transfer at the injury site. The bridges were manufactured with a gas foaming technique, and had multiple channels with controllable diameter and encapsulated plasmid. Initial studies investigating bridge implantation subcutaneously (SC) indicated transgene expression in vivo for 44 days, with gene expression dependent upon the pore size of the bridge. In the rat spinal cord, bridges implanted into a lateral hemisection supported substantial cell infiltration, aligned cells within the channels, axon growth across the channels, and high levels of transgene expression at the implant site with decreasing levels rostral and caudal. Immunohistochemistry revealed that the transfected cells at the implant site were present in both the pores and channels of the bridge and were mainly identified as Schwann cells, fibroblasts, and macrophages, in descending order of transfection. This synergy between gene delivery and the scaffold architecture may enable the engineering of tissues with complex architectures.

Intracellular delivery of protein and peptide therapeutics

Many proteins and peptides are used as highly specific and effective therapeutic agents. Their use is, however, complicated by their instability and side effects. Because many protein and peptide drugs have their therapeutic targets inside cells, there is also an important task to bring these drugs into target cells without subjecting them to the lysosomal degradation. This review describes current approaches to the intracellular delivery of protein and peptide drugs. Various drug delivery systems and methods are considered allowing for safe and effective transport of protein and peptide drugs into the cell cytoplasm.:

Targeted pharmaceutical nanocarriers for cancer therapy and imaging

The use of various pharmaceutical nanocarriers has become one of the most important areas of nanomedicine. Ideally, such carriers should be specifically delivered (targeted) to the pathological area to provide the maximum therapeutic efficacy. Among the many potential targets for such nanocarriers, tumors have been most often investigated. This review attempts to summarize currently available information regarding targeted pharmaceutical nanocarriers for cancer therapy and imaging. Certain issues related to some popular pharmaceutical nanocarriers, such as liposomes and polymeric micelles, are addressed, as are different ways to target tumors via specific ligands and via the stimuli sensitivity of the carriers. The importance of intracellular targeting of drug- and DNA-loaded pharmaceutical nanocarriers is specifically discussed, including intracellular delivery with cell-penetrating peptides.

Recent approaches to intracellular delivery of drugs and DNA and organelle targeting

Intracellular delivery of various drugs, including DNA, and drug carriers can sharply increase the efficiency of various treatment protocols. However, the receptor-mediated endocytosis of drugs, drug carriers, and DNA results in their lysosomal delivery and significant degradation. The problem can be solved and therapy efficacy still further increased if the approaches for direct intracytoplasmic delivery that bypass the endocytic pathway are developed. This is especially important for many anticancer drugs (proapoptotic drugs whose primary action site is the mitochondrial membrane) and gene therapy (nuclear or mitochondrial genomes should be targeted). This review considers several current approaches for intracellular drug delivery: the use of pH-sensitive liposomes, the use of cell-penetrating proteins and peptides, and the use of immunoliposomes targeting intracellular antigens. Among intracellular targets, nuclei (gene therapy), mitochondria (proapoptotic cancer therapy and targeting of the mitochondrial genome), and lysosomes (lysosomal targeting of enzymes for the therapy of the lysosomal storage diseases) are considered. Examples of successful intracellular and organelle-specific delivery of biologically active molecules, including DNA, are presented; unanswered questions, challenges, and future trends are also discussed.

Uptake of liposomally entrapped adenosine-3'-5'-cyclic monophosphate in mouse brain

[3H] Adenosine-3',5'-cyclic monophosphate (cAMP) could be entrapped efficiently into small unilamellar vesicles when bound to cAMP-dependent protein kinase. The leakage of [3H]cAMP protein kinase complex from liposomes was reduced by more than 60% as compared to free [3H]cAMP. Hyperosmolar mannitol increased the delivery of liposomally entrapped [3H]cAMP protein kinase to the brain with maximum uptake occurring at 10 min after mannitol administration. Optimal delivery to the brain was observed when vesicles composed of total brain lipids or phosphatidylcholine:cholesterol:sulfatides (7:2:1) were used. A slower clearance of liposomally entrapped material from brain tissue was seen under hyperosmolar conditions.

A horseradish peroxidase-light and electron microscopic study of immunoliposomes utilized for intracellular delivery to the rat striatum

Liposomes can deliver plasmid DNA, viruses, antisense oligonucleotides, and pharmacological agents to the central nervous system. Conjugation of antibodies to liposomes increases delivery specificity. Immunoliposomes created with Thy 1.1 antibody have previously been shown to be effective for neuronal delivery. The intracellular delivery of these immunoliposomes is evaluated by light and electron microscopy. Thy 1.1 conjugated liposomes were loaded with horseradish peroxidase and stereotactically injected into rat striatum. On light microscopy, immunoliposomes were concentrated within 0.2 mm of the injection site 8 h following delivery but, 24 h post-operatively, had diffused more than 0.5 mm from the injection site. With transmission electron microscopy, immunoliposomes were observed entering numerous neurons and some astrocytes in a process distinct from the clathrin-coated pit mechanism. These findings suggest that Thy 1.1 immunoliposomes are effective for intracellular delivery in vivo and their endocytosis occurs independently of a coated pit process. The research has helped to elucidate alternative mechanisms for immunoliposomal delivery. A more fundamental understanding of these attributes is needed to achieve the therapeutic potential of immunoliposomes.

Eukaryotic gene transfer with liposomes: effect of differences in lipid structure

Liposome mediated gene transfer has a great potential in gene therapy. In this review we discuss the physical and chemical properties of cationic liposomes that affect their abilities to mediate gene transfer into eukaryotic cells. The specific focus is on functional domains of cationic lipids. We address polar head variations, counterions, linker bonds, acyl chain variations, as well as composition of liposomes. We additionally discuss different functional groups of lipids affecting lipid bilayer packing, lipid association with DNA, fusion with the cellular membranes and the release of transferred DNA from endosomes into the cytoplasm.

Use of a quartz crystal microbalance to monitor immunoliposome--antigen interaction

We have used quartz crystal microbalance (QCM)-based real-time biospecific interaction measurement to analyze the binding of immunoliposomes to antigen and examined the use of liposomes as signal-enhancing reagents in competitive QCM immunoassay. For the preparation of immunoliposomes, various amounts of bacterially produced lipid-tagged single-chain antibody against 2-phenyloxazolone were incorporated in phosphatidylcholine liposomes. The immunoliposomes bound specifically to immobilized hapten, and this binding was inhibited by soluble hapten in a concentration-dependent manner. In this competitive assay, antigen could be measured in the concentration range from 10(-5) to 10(-8) M.

The principles of gene therapy for the nervous system

Research pertaining to gene transfer into cells of the nervous system is one of the fastest growing fields in neuroscience. An important application of gene transfer is gene therapy, which is based on introducing therapeutic genes into cells of the nervous system by ex vivo or in vivo techniques. With the eventual development of efficient and safe vectors, therapeutic genes, under the control of a suitable promoter, can be targeted to the appropriate neurons or glial cells. Gene therapy is not only applicable to the treatment of genetic diseases of the nervous system and the control of malignant neoplasia, but it also has therapeutic potential for acquired degenerative encephalopathies (Alzheimer's disease, Parkinson's disease), as well as for promoting neuronal survival and regeneration in various pathological states.