Microendoscopic transventricular deep brain stimulation of the anterior nucleus of the thalamus as a safe treatment in intractable epilepsy: A feasibility study

INTRODUCTION

Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is proposed in patients with severe intractable epilepsy. When used, the transventricular approach increases the risk of bleeding due the anatomy around the entry point in the thalamus. To avoid such a complication, we used a transventricular microendoscopic technique.

METHODS

We performed a retrospective study of nine adult patients who were surgically treated for refractory epilepsy between 2010 and 2019 by DBS of the anterior thalamic nucleus.

RESULTS

Endoscopy provides a direct visual control of the entry point of the lead in the thalamus through the ventricle by avoiding ependymal vessels. No hemorrhage was recorded and accuracy was systematically checked by intraoperative stereotactic MRI. We reported a responder rate improvement in 88.9% of patients at 1 year and in 87.5% at 2 years. We showed a significant decrease in global seizure count per month one year after DBS (68.1%; P=0.013) leading to an overall improvement in quality of life. No major adverse effect was recorded during the follow-up. ANT DBS showed a prominent significant effect with a decrease of the number of generalized seizures.

CONCLUSION

We aimed at a better ANT/lead collimation using a vertical transventricular approach under microendoscopic monitoring. This technique permitted to demonstrate the safety and the accuracy of the procedure.

P–055 Methylation dynamics of the sperm epigenome after chemotherapy: a case study

Study question

What is the evolution of the sperm epigenome after chemotherapy in a patient with testicular cancer (TC)?

Summary answer

These new data on epigenetic recovery profil after TC are useful tools for counseling and reassuring these patients.

What is known already

An important issue for young men affected TC is how TC and its treatment will affect, transiently or permanently, their future reproductive health. The consequences of cancer treatment on the sperm epigenome during the recovery periods are topical issues of ascendant significance as epigenetic modifications to the paternal genome may have deleterious effects on the offspring.

Study design, size, duration

Here we report the epigenomic profiling of frozen sperm from a TC patient before and after the treatment at different time points (6, 9, 12 and 24 months) by using RRBS analysis (Reduced representation bisulfite sequencing method).

Participants/materials, setting, methods

A testicular tumor (testicular germ cell tumor) was diagnosed in a 30 years old patient. A cryopreservation of spermatozoa was proposed before treatment.Semen samples were obtained 2 times before treatment and 4 times after treatment (6, 9, 12 and 24 months following the initiation of treatment).

Main results and the role of chance

Upon collection, sampling after chemotherapy ranged from 0,6 to 4,2 million per sperm straw between 6 and 24 months after the treatment, always increasing.

In order to capture the direct effect of the treatment on the methylation changes, the DMR detection has been operated between pre-chemotherapy samples (pair-wise) and the time point of 6 months. Among the 179 hqDMRs, 74 are differentially methylated between the PreCT and PostCT6m samples (16 hyper- and 68 hypo-methylated) associated with 49 DMGs (15 hyper- and 34 hypo-methylated).

We further sub-clustered the 74 hqDMRs between PreCT and PostCT6m into 6 patterns, 3 hyper- and 3 hypo-methylated. Briefly, patterns P1 and P4 include hqDMRs that quickly get back to their pre-treatment methylation status just after 9th months onwards. Patterns P2 and P5 include hqDMRs that slowly get back to their pre-treatment methylation status between 12 and 24 months after treatment. Patterns P3 and P6 include hqDMRs that remain hyper- or hypo-methylated even after 24 months.

We have intersected the genes (DMGs) associated with the detected hqDMRs with those known to be important or expressed during embryogenesis. We thus detected that 7 hyper-methylated and 6 hypomethylated DMGs were involved (or expressed) during embryonic / fetal development.

Limitations, reasons for caution

This study involves a single patient. As the patient made no major changes in his personal way of life, we hypothesized that sperm parameter variations may be attributable to the BEP treatment.

Wider implications of the findings: The altered methylated status of those DMGs important for early development might modify their expression pattern and thus affect their function during key stages of embryogenesis leading to potential developmental disorders. It is important to notice that among the 110 DMGs none of them correspond to known imprinted genes.

Trial registration number

Not applicable

Management of patients suffering from hemorrhagic intracranial metastases: Propositions to help the neurosurgeon in emergency situations based on a literature review

INTRODUCTION

Brain metastases are the most common intracranial neoplasm in adult patients, and one of the fearsome complications proves to be intratumoral hemorrhage. The neurosurgical management of patients harboring a bleeding brain metastasis is not fully established and there is still today an ongoing debate on the optimal management of these patients. The aim of this article is to provide the neurosurgeons with practical tools to assist in their decision-making process in the management of BMs.

METHODS

We conducted a literature review of the relevant Pubmed, Cochrane, and Google scholar-indexed articles published between 2000 and 2019. The following key words were entered in the Pubmed search engine: [metastasis], [metastases], [brain metastases], [brain metastasis], [hemorrhage], [hematoma], [blood clot], [intracerebral hemorrhage], [intracranial hemorrhage]. The review was performed in accordance with the PRISMA recommendations.

RESULTS

Based on PubMed, Cochrane, and Google scholar, 459 articles were retained, 392 were then removed because of their non-adequacy with the topic and, 9 articles were removed because they were not written in English language. So, 58 articles were analyzed. Radiological evaluation is crucial, but few traps exist. The frequency of overall brain tumor-related with intracranial hematoma is 7.2%, with a higher frequency for secondary tumors. The local recurrence rate after resection of a hemorrhagic metastasis seems to be better probably because of an easier "en bloc" resection thanks to the hematoma. An atypical presentation is reported in up to 4% in patients with chronic or acute subdural hematoma. Patients with subarachnoid hemorrhage and epidural hematoma are rare. A clear-cut correlation between the incidence of bleeding event in brain mets and prior stereotactic radiosurgery was not established.

CONCLUSION

The current literature pertaining to the neurosurgical management of acute bleeding in brain metastasis is scant and the level of evidence remains low (experts 'opinions; class C). Herein we suggest a flowchart to assist in dealing with those difficult patients.

Surgery for recurrent medulloblastoma: A review

INTRODUCTION

Medulloblastoma (MB) is the most common malignant brain tumour in children. Despite significant progress in its management, a proportion of children relapse; tumour recurrence still carries a poor prognosis. While surgery is a mainstay of the management of primary MB, its role in recurrent MB is unclear. The objective of this literature review is to explore current practice and potential benefits of surgery in recurrent MB.

MATERIAL AND METHODS

We reviewed all articles published in PubMed and Scholar from 1990 to 2018 with the following terms: "medulloblastoma" AND "recurrence" AND "neurosurgical procedures". Among 69 articles, 12 were directly relevant.

RESULTS

A total of 581 cases of recurrent MB were identified from published series. Median time from diagnosis to relapse was 20.4months. The majority of relapses involved disseminated craniospinal disease and only one-fifth relapses was located in the posterior fossa. The outcome was consistently poor, with a median survival of 12.4% and a median survival time after relapse of 18.5months. In the HIP-SIOP-PNET4 study, surgery at relapse was performed in 25% of cases and was associated with improved prognosis in solitary posterior fossa recurrence.

CONCLUSION

Recurrent medulloblastoma is often fatal in children who have previously received radiotherapy. The role of surgery in improving survival is unclear, but there is some evidence that resection of a focal single posterior fossa recurrence can bring survival benefit. The value of biopsy lies in the optimisation and selection of appropriate targeted therapy and in excluding a second malignancy.

TRANSPARENT TESTA 16 and 15 act through different mechanisms to control proanthocyanidin accumulation in Arabidopsis testa

Flavonoids are secondary metabolites that fulfil a multitude of functions during the plant life cycle. In Arabidopsis proanthocyanidins (PAs) are flavonoids that specifically accumulate in the innermost integuments of the seed testa (i.e. endothelium), as well as in the chalaza and micropyle areas, and play a vital role in protecting the embryo against various biotic and abiotic stresses. PAs accumulation in the endothelium requires the activity of the MADS box transcription factor TRANSPARENT TESTA (TT) 16 (ARABIDOPSIS B-SISTER/AGAMOUS-LIKE 32) and the UDP-glycosyltransferase TT15 (UGT80B1). Interestingly tt16 and tt15 mutants display a very similar flavonoid profiles and patterns of PA accumulation. By using a combination of genetic, molecular, biochemical, and histochemical methods, we showed that both TT16 and TT15 act upstream the PA biosynthetic pathway, but through two distinct genetic routes. We also demonstrated that the activity of TT16 in regulating cell fate determination and PA accumulation in the endothelium is required in the chalaza prior to the globular stage of embryo development. Finally this study provides new insight showing that TT16 and TT15 functions extend beyond PA biosynthesis in the inner integuments of the Arabidopsis seed coat.

119 A SHORT PERICONCEPTIONAL MATERNAL HYPERGLYCEMIA IS SUFFICIENT TO DISRUPT THE FETO-PLACENTAL PHENOTYPE IN A RABBIT MODEL

Pre-gestational type 1-diabetes (T1D) increases the risk of miscarriage and congenital malformations and programs the offspring to develop metabolic syndrome in adulthood. Management of maternal diabetes is essential during gestation but could be also highly important around the time of conception. Using a rabbit model, the effects of maternal T1D during the periconceptional period on pre-implantation blastocysts have been well documented, but the effects on feto-placental phenotype at 28 dpc (term = 31 days) has not been explored. Diabetes was induced by Alloxan in dams 7 days before mating. Glycemia was maintained at 15 to 20 mmol L–1 with exogenous insulin injections. At 4 dpc, embryos were collected and transferred into nondiabetic recipients. At 28 dpc, control (C) and diabetic (D) fetuses were collected for biometric records, placental analyses including stereology and gene expression, and lipid profiles of feto-placental tissues by gas chromatography. Lipid data were analysed by principal component analysis. D-fetuses were growth retarded, hyperglycemic, and dyslipidemic compared with C fetuses. Moreover, placental efficiency was much higher in D- than in C-fetuses. The volume density of fetal vessels was significantly decreased in D-placentas compared to C-placentas, whereas the volume density of trophoblast tended to increase (P = 0.051). This morphometric disruption was associated with a deregulation of the expression of genes related to nutrient supply and lipid metabolism. In fetal plasma, a specific fatty acid signature was observed in D- and C-groups. Moreover, the composition of placental and fetal liver membranes differed according to maternal status and fetal sex. Tissues from D-fetuses contained significantly more n-6 polyunsaturated fatty acids compared with C. Docosahexaenoic acid decreased whereas linoleic acid increased in the cardiac membranes of D-fetuses, indicating a higher risk of ischemia. This study demonstrates that exposure to high plasma glucose during the short periconceptional period is sufficient to adversely program fetal phenotype by reducing fetal growth, altering placental function and lipid profiles in all fetal tissues.

Non-linear optoelectronic phase-locked loop for stabilization of opto-millimeter waves: towards a narrow linewidth tunable THz source

We propose an optoelectronic phase-locked loop concept which enables to stabilize optical beat notes at high frequencies in the mm-wave domain. It relies on the use of a nonlinear-response Mach-Zehnder modulator. This concept is demonstrated at 100 GHz using a two-axis dual-frequency laser turned into a voltage controlled oscillator by means of an intracavity electrooptic crystal. A relative frequency stability better than 10⁻¹¹ is reported. This approach of optoelectronic down conversion opens the way to the realization of continuously tunable ultra-narrow linewidth THz radiation.

Beat note stabilization of a 10-60 GHz dual-polarization microlaser through optical down conversion

Down-conversion of a high-frequency beat note to an intermediate frequency is realized by a Mach-Zehnder intensity modulator. Optically-carried microwave signals in the 10-60 GHz range are synthesized by using a two-frequency solid-state microchip laser as a voltage-controlled oscillator inside a digital phase-locked loop. We report an in-loop relative frequency stability better than 2.5×10⁻¹¹. The principle is applicable to beat notes in the millimeter-wave range.

98 THE FETAL AND POSTNATAL EFFECTS OF PERICONCEPTIONAL HYPERGLYCEMIA USING A RABBIT MODEL

The objective of this study was to analyse the effects of maternal hyperglycemia during the periconception period on fetal and postnatal development using a rabbit model. Diabetes was induced in adult New Zealand female does by a single intravenous alloxan injection (group D). Glycemia was maintained between 3 and 5 g L–1 with 2 daily subcutaneous insulin injections. Does from group D and contemporary controls (group C) were naturally mated 1 wk after induction of diabetes in group D animals, without superovulation, and embryos collected after sacrifice on Day 4 post-coitum. In Expt. 1, embryos from D (n = 11) and C (n = 13) groups were transferred respectively to the right and left horns of 3 female recipients, which were killed on Day 28. In Expt. 2, 17 D and 16 C females were mated naturally. 68 D and 98 C embryos were collected and transferred to 26 non-diabetic recipients (6–7 embryos per doe). 17 females were pregnant with no difference between C and D recipients. Fetal development was monitored by ultrasound. At birth, litters were equilibrated in number. 15 D and 7 C pups (from 4 D and 2 C litters) were killed at weaning (1 month of age). The remaining 13 D and 26 C pups (4 D and 7 C litters) were allocated to 1 of 2 feeding groups: control or obesogenic diet. The obesogenic diet was based on the control diet supplemented with animal fat (suet, 200%) and glucose (200%). Bodyweight, adiposity, and glucose metabolism were monitored until sacrifice at 5 months of age. Data were analysed by ANOVA using litter (fetuses), litter and sex (weaning), and litter and diet (5 months) as co-factors. Sex effects at 5 months were not analysed due to small numbers of animals. Fetal development was not different between D and C groups. Fetal, placental, and fetal organ weights did not differ at Day 28, except for brain weight, which was significantly lower in D fetuses (0.86 ± 0.1 v. 1.05 ± 0.08 g; P < 0.05). There was no difference in litter size at birth (3.3 ± 0.3 v. 3.6 ± 0.5 pups for D and C groups, respectively; P = 0.5), but birthweight was significantly increased in D offspring (211 ± 6 v. 194 ± 6 g; P < 0.05). There was no difference in weight after 14 days. At 1 month of age, adiposity, plasma insulin and leptin concentrations were not different between groups. In contrast, in male D offspring, fasting glycemia was significantly lower (1.7 ± 0.2 v. 2.1 ± 0.02 g L–1; P < 0.01), plasma insulin-like growth factor 1 was significantly increased (P < 0.05) and kidney/bodyweight ratio was significantly reduced (0.41 ± 0.03 v. 0.45 ± 0.04; P < 0.01). From 12 wk of age, bodyweight became significantly different between D and C groups and according to diet (P < 0.005), with D individuals being lighter than C individuals for each dietary group. Finally, fasting glycemia was significantly higher in the animals fed the obesogenic diet (1.35 ± 0.05 v. 1.19 ± 0.05 g L–1; P < 0.04), regardless of group. These data suggest that maternal hyperglycemia during the periconceptional period affects glucose metabolism and organ development in offspring with sexual dimorphism.

New N(4)-substituted piperazine naphthamide derivatives as BACE-1 inhibitors

Synthesis and enzymatic evaluation of new series of N(4)-substituted piperazine naphthamide derivatives as BACE-1 inhibitors for the treatment of Alzheimer's disease are reported.

Multiple sclerosis-associated retroviral agent (MSRV)-stimulated cytokine production in patients with relapsing-remitting multiple sclerosis

Background

Human endogenous retroviruses are suggested to play a pathogenic role in multiple sclerosis (MS); one of such retroviruses, the MS-associated retroviral agent (MSRV) has repeatedly been isolated in MS patients.

Objective and methods

We analyzed cytokine profiles in MSRV envelope protein (MSRV ENV-SU)-stimulated peripheral blood mononuclear cells of 30 relapsing-remitting MS patients with either acute (AMS) ( n = 13) or stable (SMS) ( n = 17) disease. Results suggest that MSRV ENV-SU induces the production of inflammatory cytokines, including tumor necrosis factor-α ( P < 0.05) and interferon-γ ( P < 0.004) in AMS patients and of interleukin-10 ( P < 0.05), an inflammation-dampening cytokine, in SMS individuals.

Conclusions

These data strengthen the hypothesis indicating that MSRV could be involved in the pathogenesis of MS.

Peptide-mediated Gene Transfer of Cationic Lipid/Plasmid DNA Complexes to Endothelial Cells

The purpose of this research is to develop ligand-targeted plasmid based gene delivery systems for gene transfer to tumor endothelium. Cell adhesion assays were used to test the peptide inhibition of human endothelial cell adsorption to vitronectin-treated tissue culture plates. A series of RGD containing peptides were tested in linear form and with one and two disulfide bonds. The linear and two disulfide bond peptides yielded similar IC50 (approximately 1 x 10(-7) M). Substitution of two methionines for cysteines yielded a single disulfide bond that increased the IC50 by 10-fold. The single and double disulfide peptides were derivatized to N-succinyl-dioleoylphopsphatidylethanolamine and incorporated into 100 nm liposomes radiolabeled with H-cholesterylhexadecylether. Liposome uptake by human umbilical vein endothelial cells was tested as a function of lipopeptide surface density. Increase in membrane surface density from 5 to 20mol% increased human umbilical derived endothelial cell (HUVEC) uptake of the liposomes for both the single and double disulfide peptides. Liposome uptake by HUVECs was 3-fold greater for the double disulfide compared to the single disulfide. The single and double disulfide lipopeptides were then tested for gene transfer to HUVECs using DOTMA:Cholesterol cationic liposomes. The polyplexes were formed by rapidly mixing plasmid DNA with DOTMA:CHOL liposomes at a 3:1 charge ratio in 2% ethanol, 10% lactose. The ethanol was removed by lyophilization and upon rehydration, the lipoplexes had a mean diameter of approximately 100nm. HUVEC transfection studies showed that increasing the mol% of the single disulfide RGD lipopeptide to 20mol% increased gene transfer by 10-fold. This increase in transfection could be reduced to that obtained in the absence of lipopeptide by co-incubating the HUVECs with a 100-fold excess of the single disulfide RGD peptide, thus demonstrating lipopeptide mediated gene transfer to endothelial cells.

Multiple sclerosis-associated retrovirus particles cause T lymphocyte-dependent death with brain hemorrhage in humanized SCID mice model

A retroviral element (multiple sclerosis-associated retrovirus, MSRV) defining a family of genetically inherited endogenous retroviruses (human endogenous retrovirus type W, HERV-W) has been characterized in cell cultures from patients with multiple sclerosis. Recently, MSRV retroviral particles or the envelope recombinant protein were shown to display superantigen activity in vitro, but no animal model has yet been set up for studying the pathogenicity of this retrovirus. In the present study, the pathogenicity of different sources of MSRV retroviral particles has been evaluated in a hybrid animal model: severe combined immunodeficiency (SCID) mice grafted with human lymphocytes and injected intraperitoneally with MSRV virion or mock controls. MSRV-injected mice presented with acute neurological symptoms and died within 5 to 10 days post injection. Necropsy revealed disseminated and major brain hemorrhages, whereas control animals did not show abnormalities (P <.001). In ill animals, reverse transcriptase-polymerase chain reaction (RT-PCR) analyses showed circulating MSRV RNA in serum, whereas overexpression of proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma was evidenced in spleen RNA. Neuropathological examination confirmed that hemorrhages occurred prior to death in multifocal areas of brain parenchyma and meninges. Further series addressed the question of immune-mediated pathogenicity, by inoculating virion to SCID mice grafted with total and T lymphocyte-depleted cells in parallel: dramatic and statistically significant reduction in the number of affected mice was observed in T-depleted series (P <.001). This in vivo study suggests that MSRV retroviral particles from MS cultures have potent immunopathogenic properties mediated by T cells compatible with the previously reported superantigen activity in vitro, which appear to be mediated by an overexpression of proinflammatory cytokines.

[Evaluation of lip damage]

The evaluation of permanent labial damage by medico-legal expertise takes in consideration the patient's past history and his suffering moral and physical, as well as objective physical examination and its correlation with patient's claim. The medico-legal discussion that follows should provide the necessary arguments to fix the consolidation date, determine the origin of sequellae and to evaluate the resulting prejudice. Among those, evaluation of esthetic prejudice is quite delicate as there are no universally admitted criteria of evaluation. The estimation of the functional deficit is done by reference to an evaluation chart. The expert should take in consideration the particular effect of the sequellae on the patient's professional and personal activities.

Immune and clinical responses in patients with metastatic melanoma to CD34(+) progenitor-derived dendritic cell vaccine

Immunization to multiple defined tumor antigens for specific immune therapy of human cancer has thus far proven difficult. Eighteen HLA A*0201(+) patients with metastatic melanoma received injections s.c. of CD34(+)progenitor-derived autologous dendritic cells (DCs), which included Langerhans cells. DCs were pulsed with peptides derived from four melanoma antigens [(MelAgs) MelanA/MART-1, tyrosinase, MAGE-3, and gp100], as well as influenza matrix peptide (Flu-MP) and keyhole limpet hemocyanin (KLH) as control antigens. Overall immunological effects were assessed by comparing response profiles using marginal likelihood scores. DC injections were well tolerated except for progressive vitiligo in two patients. DCs induced an immune response to control antigens (KLH, Flu-MP) in 16 of 18 patients. An enhanced immune response to one or more MelAgs was seen in these same 16 patients, including 10 patients who responded to >2 MelAgs. The two patients failing to respond to both control and tumor antigens experienced rapid tumor progression. Of 17 patients with evaluable disease, 6 of 7 patients with immunity to two or less MelAgs had progressive disease 10 weeks after study entry, in contrast to tumor progression in only 1 of 10 patients with immunity to >2 MelAgs. Regression of >1 tumor metastases were observed in seven of these patients. The overall immunity to MelAgs after DC vaccination is associated with clinical outcome (P = 0.015).

Neurophysiological effects of an extract of Eschscholzia californica Cham. (Papaveraceae)

An aqueous alcohol extract of Eschscholzia californica (Ec) has been evaluated for benzodiazepine, neuroleptic, antidepressant, antihistaminic and analgesic properties, in order to complete the study of the sedative and anxiolytic effects previously demonstrated. The plant extract did not protect mice against the convulsant effects of pentylenetetrazol, and did not cause muscle relaxant effects but appeared to possess an affinity for the benzodiazepine receptor: thus, flumazenil, an antagonist of these receptors, suppressed the sedative and anxiolytic effects of the extract. The Ec extract induced peripheral analgesic effects in mice but did not possess antidepressant, neuroleptic or antihistaminic effects.

Fusogenic activity of vesicular stomatitis virus glycoprotein plasmid in tumors as an enhancer of IL-12 gene therapy

We have characterized the fusogenic activity of a plasmid expression system encoding vesicular stomatitis virus G protein (VSVG) in vitro and in vivo. Over 70% of murine colon and renal carcinoma cells (MC38 and Renca, respectively) transfected with VSVG plasmid in vitro fused and formed polykaryons upon incubation with pH 5.5 media. Using a plasmid expression system encoding VSVG and bacterial green fluorescent protein (GFP) formulated in a polyvinyl pyrrolidone (PVP) delivery system, diffusion of GFP throughout the VSVG-induced syncytia was shown in vivo in MC38 and Renca tumors. Moreover, tumor-bearing mice showed tumor growth inhibition following in vivo transfection with VSVG plasmid at an optimal dose of 48 microg. We have previously shown that direct injection of interleukin -12 (IL -12) plasmid complexed with PVP into tumors induces a strong immune response. In the current study, we assessed the ability of VSVG to elicit an antitumor response by enhancing cytokine gene delivery within the tumor mass. Tumor-bearing mice treated intratumorally with both VSVG/PVP and IL-12/PVP (48 and 24 microg, respectively) showed increase in tumor rejection when compared to IL- 12 plasmid alone (75% vs. 50%, respectively). These data suggest that VSVG gene therapy can be used in combination with other therapeutic genes to induce an antitumor response in vivo by enhancing the expression of the gene of interest.

Ultrasound enhancement of cationic lipid-mediated gene transfer to primary tumors following systemic administration

The impact of a localized application of ultrasound on gene transfer to primary tumors following systemic administration of cationic lipid based transfection complexes was investigated. We have previously shown that systemic administration of DOTMA (N-[(1-(2-3-dioleyloxy) propyl)]-N-N-N-trimethylammonium chloride):cholesterol-based transfection complexes to tumor-bearing mice resulted in expression in the tumor and other tissues, primarily the lungs. Application of ultrasound to the tumor before or after the injection resulted in a significant increase in gene transfer to the tumor with no increase observed in other tissues. The magnitude of increased expression ranged from three- to 270-fold depending upon the DNA dose. The following parameters were optimized for maximal increase: duration of ultrasound application, the time interval between plasmid injection and sonoporation, and plasmid dose. A combination of plasmid quantitation and fluorescence microscopy showed that ultrasound increased tumor uptake of the plasmid and that uptake was limited to the tumor vasculature. Using an IL- 12 expression plasmid, the combination of a single plasmid dose (10 microg) and ultrasound treatment produced significantly higher levels of IL-12 in tumor. This increased expression was sufficient to inhibit tumor growth compared with the control conditions. These data demonstrate the potential application of sonoporation as an effective method for enhancing the expression of systemically administered genes in tumor endothelium for cancer gene therapy.

Optimization of cationic lipid/DNA complexes for systemic gene transfer to tumor lesions

Intravenous (i.v.) administration of cationic lipid N-[( 1-(2-3-dioleyloxy)propyl)]-N-N-N-trimethylammonium chloride (DOTMA)-based transfection complexes in mice with subcutaneous squamous cell tumors yielded plasmid delivery and expression in tumor lesions. The efficiency of gene transfer in tumors was significantly lower than in the lung. This was consistent with low plasmid levels associated with the tumor, suggesting that plasmid delivery to the tumor site was a limiting factor. Lowering the lipid/DNA charge ratio from 5:1 to 0.8:1 (+/-) did not change DNA levels in tumor but significantly reduced DNA levels in lung. However, expression levels were significantly reduced in both tissues at lower lipid/DNA charge ratios. Complexes prepared from small unilamellar liposomes gave significantly lower expression levels in the lungs but similar expression levels in tumors when compared to complexes prepared from larger unilamellar liposomes. The small liposome complexes were better tolerated than large liposome complexes. Varying the cationic lipid to colipid (cholesterol or DOPE) molar ratio from 4: 1 to 1: 1 significantly reduced expression levels in both tumor and lung. Cationic lipid substitution, using a cholesterol cationic lipid, diethyldiamino-carbamyl-cholesterol instead of DOTMA, produced reduced expression in all other tissues except tumor. Incorporation of PEG into preformed transfection complexes reduced DNA delivery to lung, increased circulation half-life, and enhanced DNA delivery to tumor. In a lung metastatic mouse tumor model, where the accessibility of the i.v. administered transfection complexes to tumor lesions should be less challenging, DOTMA: CHOL complexes (4: 1 lipid to colipid molar ratio, 3: 1 +/- lipid to plasmid charge ratio) were preferentially localized in tumor lesions. These data demonstrate that systemic gene transfer to distal tumor sites by lipid/ DNA complexes may be limited by low plasmid delivery. Modifying the chemical surface properties of transfection complexes enhanced both DNA delivery and expression in tumor and is one approach that may overcome limitations.

Topoisomerase I-mediated antiproliferative activity of enantiomerically pure fluorinated homocamptothecins

Homocamptothecin (hCPT) is an E-ring modified camptothecin (CPT) analogue bearing a methylene spacer between the alcohol and carboxyl functions of the CPT lactone. Combining pronounced inhibitory activity of topoisomerase I (Topo I) with enhanced plasma stability, hCPT constitutes an attractive template for the elaboration of new anticancer agents. Fluorinated hCPT analogues, prepared in enantiomerically pure form, were assayed by their stimulation of Topo I-mediated DNA cleavage. Translation into cytotoxicity against tumor cells was evaluated on HT29 human colon adenocarcinoma and on the multidrug resistant lung and bladder tumor cell lines, A549 and T24r. Good correlation is observed between the ability of the drugs to stimulate Topo I-mediated DNA cleavage and the respective 50% inhibitory concentrations (IC(50) values) of the HT29, A549, and T24r cell growth. Fluorine substitution in the A-ring of hCPT was found to have a pronounced influence on biological activity, providing several compounds which are up to 100-fold more potent than CPT in terms of IC(50). Among these, 10,11-difluoro-hCPT has been selected for further development.

Synthetic glycopeptide-based delivery systems for systemic gene targeting to hepatocytes

PURPOSE

To design, synthesize, and test synthetic glycopeptide-based delivery systems for gene targeting to hepatocytes by systemic administration.

METHODS

All peptides were synthesized by the solid phase method developed using Fmoc chemistry on a peptide synthesizer. The binding of galactosylated peptides to HepG2 cells and accessibility of the galactose residues on particle surface was demonstrated by a competition assay using 125I-labeled asialoorosomucoid and RCA lectin agglutination assay, respectively. DNA plasmid encoding chloramphenicol acetyl transferase (CAT) gene was complexed with a tri-galactosylated peptide (GM245.3) or tri-galactosylated lipopeptide (GM246.3) in the presence of an endosomolytic peptide (GM225.1) or endosomolytic lipopeptide (GM227.3) to obtain DNA particles of 100-150 nm in size. The plasmid/peptide complexes were added to HepG2 cell cultures or intravenously administered by tail vein injection into normal mice or rats. Plasmid uptake and expression was quantified by qPCR and ELISA, respectively.

RESULTS

Multiple antennary glycopeptides that have the ability to condense and deliver DNA plasmid to hepatocytes were synthesized and complexed with DNA plasmid to obtain colloidally stable DNA/peptide complexes. Addition of DNA/GM245.3/GM225.1 peptide complexes (1:3:1 (-/+/-)) to HepG2 cell cultures yielded CAT expression in transfected cells. The transfection efficiency was significantly reduced in the absence of galactose ligand or removal of endosomolytic peptide. Intravenous administration of DNA/GM245.3 peptide complexes (1:0.5 (-/+)) into the tail vein of normal rats yielded DNA uptake in the liver. Substitution of GM245.3 by galactosylated lipopeptide GM246.3 resulted in more stable DNA particles, and a 10-fold enhancement in liver plasmid uptake. CAT expression was detectable in liver following intravenous administration of DNA/GM246.3 complexes. Addition of endosomolytic lipopeptide GM227.3 into the complexes (DNA/ GM246.3/GM227.3 (1:0.5:1 (-/+/-))) yielded a 5-fold increase in CAT expression. Liver expression was 8-fold and 40-fold higher than lung and spleen, respectively, and localized in the hepatocytes only. The transfection efficiency in liver was enhanced by increasing DNA dose and injection volume. The plasmid uptake and expression in liver using DNA/GM246.3/GM227.3 complexes was 100-200-fold higher than DNA formulated in glucose. Tissue examination and serum biochemistry did not show any adverse effect of the DNA/GM246.3/ GM227.3 (1:0.5:1 (-/+/-)) complexes after intravenous delivery.

CONCLUSIONS

Gene targeting to hepatocytes was achieved by systemic administration of a well-tolerated synthetic glycopeptide-based delivery system. The transfection efficiency of this glycopeptide delivery system was dependent on peptide structure, endosomolytic activity, colloidal particle stability, and injection volume.

Pharmaceutical perspectives of nonviral gene therapy

The use of nonviral plasmid-based gene medicines represents an attractive in vivo gene transfer strategy that is simple and lacks many risks that are inherent to viral systems. Commercialization of gene medicines requires a thorough analysis of business opportunities, unmet clinical needs, competitive products under development, and issues related to intellectual property. Synthetic gene delivery systems are designed to control the location of a gene within the body by affecting distribution and access of a gene expression system to the target cell, and/or recognition by a cell surface receptor and uptake followed by intracellular and nuclear translocation. Plasmid-based gene expression systems are designed to control the level, fidelity, and duration of in vivo production of a therapeutic gene product. This review will provide insights into the potentials of plasmid-based gene therapy and critical evaluation of gene delivery sciences and clinical applications of gene medicines.

BN 80927: a novel homocamptothecin with inhibitory activities on both topoisomerase I and topoisomerase II

BN 80927, a novel homocamptothecin derivative, inhibits both topoisomerase I and topoisomerase II mediated DNA relaxation and shows pronounced cytotoxicity against HT29, SKOV-3, DU145 and MCF7 human tumor cell lines.

Crystal structure of Pseudomonas fluorescens 4-hydroxyphenylpyruvate dioxygenase: an enzyme involved in the tyrosine degradation pathway

BACKGROUND

In plants and photosynthetic bacteria, the tyrosine degradation pathway is crucial because homogentisate, a tyrosine degradation product, is a precursor for the biosynthesis of photosynthetic pigments, such as quinones or tocophenols. Homogentisate biosynthesis includes a decarboxylation step, a dioxygenation and a rearrangement of the pyruvate sidechain. This complex reaction is carried out by a single enzyme, the 4-hydroxyphenylpyruvate dioxygenase (HPPD), a non-heme iron dependent enzyme that is active as a homotetramer in bacteria and as a homodimer in plants. Moreover, in humans, a HPPD deficiency is found to be related to tyrosinemia, a rare hereditary disorder of tyrosine catabolism.

RESULTS

We report here the crystal structure of Pseudomonas fluorescens HPPD refined to 2.4 A resolution (Rfree 27.6%; R factor 21.9%). The general topology of the protein comprises two barrel-shaped domains and is similar to the structures of Pseudomonas 2,3-dihydroxybiphenyl dioxygenase (DHBD) and Pseudomonas putida catechol 2,3-dioxygenase (MPC). Each structural domain contains two repeated betaalpha betabeta betaalpha modules. There is one non-heme iron atom per monomer liganded to the sidechains of His161, His240, Glu322 and one acetate molecule.

CONCLUSIONS

The analysis of the HPPD structure and its superposition with the structures of DHBD and MPC highlight some important differences in the active sites of these enzymes. These comparisons also suggest that the pyruvate part of the HPPD substrate (4-hydroxyphenylpyruvate) and the O2 molecule would occupy the three free coordination sites of the catalytic iron atom. This substrate-enzyme model will aid the design of new inhibitors of the homogentisate biosynthesis reaction.

Systemic inhibition of tumor growth and tumor metastases by intramuscular administration of the endostatin gene

Tumors require ongoing angiogenesis to support their growth. Inhibition of angiogenesis by production of angiostatic factors should be a viable approach for cancer gene therapy. Endostatin, a potent angiostatic factor, was expressed in mouse muscle and secreted into the bloodstream for up to 2 weeks after a single intramuscular administration of the endostatin gene. The biological activity of the expressed endostatin was demonstrated by its ability to inhibit systemic angiogenesis. Moreover, the sustained production of endostatin by intramuscular gene therapy inhibited both the growth of primary tumors and the development of metastatic lesions. These results demonstrate the potential utility of intramuscular delivery of an antiangiogenic gene for treatment of disseminated cancers.

Peptide-based gene delivery

To achieve effective plasmid-based gene therapy, the control of cellular access and uptake, intracellular trafficking and nuclear retention of plasmids must be achieved. Inefficient endosomal release, cytoplasmic transport and nuclear entry of plasmids are amongst some of the key limiting factors in the use of plasmids for effective gene therapy. A number of non-viral gene delivery systems have been designed to overcome these limiting factors. The most common approach to protect and control plasmid distribution is to complex plasmids with cationic lipids or polymers through electrostatic interactions. Endosomal release of plasmids can be achieved, for instance, by using pH-sensitive lipids, inactivated viral particles, endosomolytic peptides and polymers. Among the least explored gene delivery systems are those that consist mainly of synthetic, short peptides. Peptides can be incorporated into multicomponent gene delivery complexes for specific purposes, such as for DNA condensation, cell-specific targeting, endosomolysis or nuclear transport. The aims of this review are to: (i) explore the conceptual and experimental aspects of peptide-DNA interactions; (ii) critically assess the possible use of peptides for efficient gene transfer; and (iii) present an overview on the use of peptides to enhance the effectiveness of other gene delivery systems. On balance, peptide-based gene delivery systems appear to have a significant potential as commercially viable gene delivery products.

Homocamptothecins: synthesis and antitumor activity of novel E-ring-modified camptothecin analogues

Homocamptothecin (hCPT), a camptothecin (CPT) analogue with a seven membered beta-hydroxylactone which combines enhanced plasma stability and potent topoisomerase I (Topo I)-mediated activity, is an attractive template for the elaboration of new anticancer agents. Like CPT, hCPT carries an asymmetric tertiary alcohol and displays stereoselective inhibition of Topo I. The preparation and biological screening of racemic hCPT analogues are described. The 10 hCPTs tested were better Topo I inhibitors than CPT. Fluorinated hCPTs 23c, d,f,g were found to have potent cytotoxic activity on A427 and PC-3 tumor cell lines. Their cytotoxicity remained high on the K562adr and MCF7mdr cell lines, which overexpress a functionally active P-glycoprotein. Fluorinated hCPTs were more efficacious in vivo than CPT on HT-29 xenografts. In this model, a tumor growth delay of 25 days was reached with hCPT 23g at a daily dose of 0.32 mg/kg, compared to 4 days with CPT at 0.625 mg/kg. Thus difluorinated hCPT 23g warrants further investigation as a novel Topo I inhibitor with high cytotoxicity toward tumor cells and promising in vivo efficacy.

Ultrasonic nebulization of cationic lipid-based gene delivery systems for airway administration

PURPOSE

This study relates to the development of gene therapies for the treatment of lung diseases. It describes for the first time the use of ultrasonic nebulization for administration of plasmid/lipid complexes to the lungs to transfect lung epithelial cells.

METHODS

Plasmid complexed to cationic liposomes at a specific stoichiometric ratio was nebulized using an ultrasonic nebulizer. We assessed: (i) the stability of plasmid and plasmid/lipid complexes to ultrasonic nebulization, (ii) the in vitro activity of plasmid in previously nebulized plasmid/lipid complex, (iii) the in vivo transgene expression in lungs following intratracheal instillation of nebulized plasmid/lipid formulations compared to un-nebulized complexes, (iv) the emitted dose from an ultrasonic nebulizer using plasmid/lipid complexes of different size, and (v) the transgene expression in lungs following oral inhalation of aerosolized plasmid/lipid complex generated using an ultrasonic nebulizer.

RESULTS

Integrity of plasmid formulated with cationic lipids, and colloidal stability of the plasmid/lipid complex were maintained during nebulization. In contrast, plasmid alone formulated in 10% lactose was fragmented during nebulization. The efficiency of transfection of the complex before and after nebulization was comparable. Nebulization produced respirable aerosol particles. Oral exposure of rodents for 10 minutes to aerosol produced from the ultrasonic nebulizer resulted in transgene expression in lungs in vivo.

CONCLUSIONS

The performance characteristics of the ultrasonic nebulizer with our optimized plasmid/lipid formulations suggests that this device can potentially be used for administering gene medicines to the airways in clinical settings for the treatment of respiratory disorders.

Long-term connexin-mediated bystander effect in highly tumorigenic human cells in vivo in herpes simplex virus thymidine kinase/ganciclovir gene therapy

Gene therapy via the herpes simplex virus thymidine kinase (tk) gene and ganciclovir (GCV) treatment eliminates experimental tumors. In this approach, cells expressing the tk gene (tk+) and neighboring tumor cells which do not express the gene are killed. We have demonstrated this bystander effect is enhanced in vitro by gap junctional intercellular communication (GJIC). In order to extend our in vitro results into in vivo situations, we injected into nude mice different ratios of tk+/tk- HeLa cells, either lacking or transfected with connexin43 (Cx43), a gene coding for a gap junction protein. When GCV was administered before tumors were palpable, fewer animals developed tumors, even after a longer period, if the injected cells were mixtures of Cx43(+)-tk+ and Cx43(+)-tk- while tumor growth was not prevented with mixtures of HeLa cells not expressing Cx43, i.e. Cx43(+)-tk+/Cx43(-)-tk-. When GCV was given after the appearance of tumors, the size of the tumors from Cx43- cells was 30% reduced for 3 weeks if 50% of the injected cells were tk+. However, for cells expressing Cx43, the tumor size was 66% reduced if 10% of the cells were tk+. Such a reduction demonstrates a long-term bystander effect which is dependent on Cx43 expression.

Biodistribution and gene expression of lipid/plasmid complexes after systemic administration

The objectives of this study were to investigate the influence of physicochemical properties of lipid/plasmid complexes on in vivo gene transfer and biodistribution characteristics. Formulations based on 1,2-di-O-octadecenyl-3-trimethylammonium propane (DOTMA) and novel biodegradable cationic lipids, such as ethyl dioleoyl phosphatidylcholine (EDOPC), ethyl palmitoyl myristyl phosphatidylcholine (EPMPC), myristyl myristoyl carnitine ester (MMCE), and oleyl oleoyl L-carnitine ester (DOLCE), were assessed for gene expression after tail vein injection of lipid/plasmid complexes in mice. Gene expression was influenced by cationic lipid structure, cationic lipid-to-colipid molar ratios, plasmid-to-lipid charge ratios, and precondensation liposome size. Detectable levels of human growth hormone (hGH) in serum, human factor IX (hFIX) in plasma, and chloramphenicol acetyltransferase (CAT) in the lung and liver were observed with positively charged lipid/plasmid complexes prepared from 400-nm extruded liposomes with a cationic lipid-to-colipid ratio of 4:1 (mol/mol). Intravenous administration of lipid/CAT plasmid complexes resulted in distribution of plasmid DNA mainly to the lung at 15 min after injection. Plasmid DNA accumulation in the liver increased with time up to 24 hr postinjection. There was a 10-fold decrease in the amount of plasmid DNA in the lung at 15 min after injection, when the lipid/plasmid complex charge ratio was decreased from 3:1 to 0.5:1 (+/-). Bright fluorescent aggregates were evident in in vivo-transfected lung with the positively charged pCMV-CAT/DOLCE:dioleyl phosphatidylethanolamine (DOPE) (1:1, mol/mol) complexes, while more discrete punctate fluorescence was observed with a 4:1 molar ratio of cationic lipid:colipid formulations. Preinjection of polyanions such as plasmid, dextran sulfate, polycytidic acid, and polyinosinic acid decreased hGH expression, whereas the preinjection of both positively charged and neutral liposomes had no effect on hGH serum levels. Of the cationic lipids tested, DOLCE was found to be the most effective potentially biodegradable cationic lipid. A correlation between gene expression and cationic lipid:colipid ratios and lipid-to-plasmid charge ratio was also observed for DOTMA- and DOLCE-based formulations.

Target specific optimization of cationic lipid-based systems for pulmonary gene therapy

PURPOSE

Cationic lipids are capable of transferring foreign genes to the pulmonary epithelium in vivo. It is becoming increasingly clear that factors other than lipid molecular structure also influence efficiency of delivery using cationic lipid systems. This study is aimed at evaluating the effect of formulation variables such as cationic lipid structure, cationic lipid/DNA ratio, particle size, co-lipid content and plasmid topology on transgene expression in the lung.

METHODS

The effect of varying the surface and colloidal properties of cationic lipid-based gene delivery systems was assessed by intratracheal instillation into rats. An expression plasmid encoding chloramphenicol acetyl transferase (CAT) was used to measure transgene expression.

RESULTS

Cationic lipid structure, cationic lipid/DNA ratio, particle size, co-lipid content and topology of the plasmid, were found to significantly affect transgene expression. Complexation with lipids was found to have a protective effect on DNA integrity in bronchoalveolar lavage fluid (BALF). DNA complexed with lipid showed enhanced persistence in rat lungs as measured by quantitative polymerase chain reaction.

CONCLUSIONS

Fluorescence microscopy analysis indicated that the instilled formulation reaches the lower airways and alveolar region. Data also suggests cationic lipid-mediated gene expression is primarily localized in the lung parenchyma and not infiltrating cells isolated from the BALF.

A physicochemical approach for predicting the effectiveness of peptide-based gene delivery systems for use in plasmid-based gene therapy

Novel synthetic peptides, based on carrier peptide analogs (YKAKnWK) and an amphipathic peptide (GLFEALLELLESLWELLLEA), have been formulated with DNA plasmids to create peptide-based gene delivery systems. The carrier peptides are used to condense plasmids into nanoparticles with a hydrodynamic diameter (DH) ranging from 40 to 200 nm, which are sterically stable for over 100 h. Size and morphology of the carrier peptide/plasmid complex have been determined by photon correlation spectroscopy (PCS) and transmission electron microscopy (TEM), respectively. The amphipathic peptide is used as a pH-sensitive lytic agent to facilitate release of the plasmid from endosomes after endocytosis of the peptide/plasmid complex. Hemolysis assays have shown that the amphipathic peptide destabilizes lipid bilayers at low pH, mimicking the properties of viral fusogenic peptides. However, circular dichroism studies show that unlike the viral fusion peptides, this amphipathic peptide loses some of its alpha-helical structure at low pH in the presence of liposomes. The peptide-based gene delivery systems were tested for transfection efficiency in a variety of cell lines, including 14-day C2C12 mouse myotubes, using gene expression systems containing the beta-galactosidase reporter gene. Transfection data demonstrate a correlation between in vitro transfection efficiency and the combination of several physical properties of the peptide/plasmid complexes, including 1) DNA dose, 2) the zeta potential of the particle, 3) the requirement of both lytic and carrier peptides, and 4) the number of lysine residues associated with the carrier peptide. Transfection data on 14-day C2C12 myotubes utilizing the therapeutic human growth hormone gene formulated in an optimal peptide gene delivery system show an increase in gene expression over time, with a maximum in protein levels at 96 h (approximately 18 ng/ml).

Expression of biologically active human insulin-like growth factor-I following intramuscular injection of a formulated plasmid in rats

Recent evidence has shown that insulin-like growth factor-I (IGF-I) plays an important role in the development, maintenance, and regeneration of peripheral nerves and skeletal muscle. IGF-I offers the potential to treat neuromuscular diseases in humans. We have developed a nonviral gene therapy method to express and produce localized and sustained therapeutic levels of IGF-I within target muscles by intramuscular injection of formulated plasmids. The purpose of the present study was to demonstrate that intramuscular injection of a plasmid encoding human IGF-I (hIGF-I) and engineered to restrict expression to skeletal muscle produces sustained local concentrations of biologically active hIGF-I. Normal rats received a single intramuscular injection of plasmids formulated as a complex with polyvinylpyrrolidone (PVP). Results show that hIGF-I mRNA and hIGF-I protein were detectable in the injected muscles for the duration of the study (28 days), whereas the hIGF-I protein was not detected in blood. Biological activity of hIGF-I was determined by immunodetection of a nerve-specific growth-associated protein, GAP-43, an indicator of motor neuron sprouting. Placement of human growth hormone (hGH) 3' untranslated region enhanced GAP-43 staining, probably due to improved secretion of hIGF-I. Enhanced immunoreactivity of GAP-43 was observed in muscles injected with the formulated hIGF-I plasmid when compared to controls. These results demonstrate that intramuscular injection of hIGF-I plasmid formulated as a complex with PVP produces a localized and sustained level of biologically active hIGF-I.

Subcellular localization and purification of a p-hydroxyphenylpyruvate dioxygenase from cultured carrot cells and characterization of the corresponding cDNA

p-Hydroxyphenylpyruvate dioxygenase catalyses the transformation of p-hydroxyphenylpyruvate into homogentisate. In plants this enzyme has a crucial role because homogentisate is the aromatic precursor of all prenylquinones. Furthermore this enzyme was recently identified as the molecular target for new families of potent herbicides. In this study we examine precisely the localization of p-hydroxyphenylpyruvate dioxygenase activity within carrot cells. Our results provide evidence that, in cultured carrot cells, p-hydroxyphenylpyruvate dioxygenase is associated with the cytosol. Purification and SDS/PAGE analysis of this enzyme revealed that its activity is associated with a polypeptide of 45-46 kDa. This protein specifically cross-reacts with an antiserum raised against the p-hydroxyphenylpyruvate dioxygenase of Pseudomonas fluorescens. Gel-filtration chromatography indicates that the enzyme behaves as a homodimer. We also report the isolation and nucleotide sequence of a cDNA encoding a carrot p-hydroxyphenylpyruvate dioxygenase. The nucleotide sequence (1684 bp) encodes a protein of 442 amino acid residues with a molecular mass of 48094 Da and shows specific C-terminal regions of similarity with other p-hydroxyphenylpyruvate dioxygenases. This cDNA encodes a functional p-hydroxyphenylpyruvate dioxygenase, as evidenced by expression studies with transformed Escherichia coli cells. Comparison of the N-terminal sequence of the 45-46 kDa polypeptide purified from carrot cells with the deduced peptide sequence of the cDNA confirms that this polypeptide supports p-hydroxyphenylpyruvate dioxygenase activity. Immunodetection studies of the native enzyme in carrot cellular extracts reveal that N-terminal proteolysis occurs during the process of purification. This proteolysis explains the difference in molecular masses between the purified protein and the deduced polypeptide.

Cationic lipid-based gene delivery systems: pharmaceutical perspectives

Gene delivery systems are designed to control the location of administered therapeutic genes within a patient's body. Successful in vivo gene transfer may require (i) the condensation of plasmid and its protection from nuclease degradation, (ii) cellular interaction and internalization of condensed plasmid, (iii) escape of plasmid from endosomes (if endocytosis is involved), and (iv) plasmid entry into cell nuclei. Expression plasmids encoding a therapeutic protein can be, for instance, complexed with cationic liposomes or micelles in order to achieve effective in vivo gene transfer. A thorough knowledge of pharmaceutics and drug delivery, bio-engineering, as well as cell and molecular biology is required to design optimal systems for gene therapy. This mini-review provides a critical discussion on cationic lipid-based gene delivery systems and their possible uses as pharmaceuticals.

Determination of the surface tension of block copolymer micelles by phagocytosis

PURPOSE

This work was carried out to determine the surface tension of block copolymer micelles of 14C labelled ABA poly (oxyethylene-bi-isoprene-b-oxyethylene) which have a long circulating half life in animals.

METHODS

The method used was that of phagocytosis. The percentage of micelles phagocytosed by human mononuclear cells was determined in solutions of different surface tension.

RESULTS

The values obtained were 72 mN/m which may be predicted for a particle with a long circulating half life in animals. The method also gave an estimate of the surface tension for the mononuclear cells.

CONCLUSIONS

This technique has the advantage of determining the surface tension of highly hydrated small particles including stable micelles in an environment similar to that in which they normally exist.