Design and Evaluation of RGD-Modified Gemini Surfactant-Based Lipoplexes for Targeted Gene Therapy in Melanoma Model

PURPOSE

We have developed and evaluated novel peptide-targeted gemini surfactant-based lipoplexes designed for melanoma gene therapy.

METHODS

Integrin receptor targeting peptide, cyclic-arginylglycylaspartic acid (cRGD), was either chemically coupled to a gemini surfactant backbone or physically co-formulated with lipoplexes. Several formulations and transfection techniques were developed. Transfection efficiency and cellular toxicity of the lipoplexes were evaluated in an in vitro human melanoma model. Physicochemical properties were examined using dynamic light scattering, zeta-potential, and small-angle X-ray scattering measurements.

RESULTS

RGD-modified gemini surfactant based lipoplexes showed significant enhancement in gene transfection activity in A375 cell lines compared to the standard non-targeted formulation, especially when RGD was chemically conjugated to the gemini surfactant (RGD-G). The RGD had no effect on the cell toxicity profile of the lipoplex systems. Targeting specificity was confirmed by using an excess of free RGD and negative control peptide (RAD) and was demonstrated by using normal human epidermal keratinocytes. Physicochemical characterization showed that all nanoparticles were in the optimal size range for cellular uptake and there were no significant differences between RGD-modified and standard lipoplexes.

CONCLUSIONS

These findings indicate the potential of RGD-modified gemini surfactant-based lipoplexes for use in melanoma gene therapy as an alternative to conventional chemotherapy.

Evaluation of β-cyclodextrin-modified gemini surfactant-based delivery systems in melanoma models

Novel drug delivery systems are developed to improve the biological behavior of poorly soluble drugs and to improve therapeutic outcomes. In melanoma therapy, the goal is efficient drug delivery and mitigation of drug resistance. Melphalan (Mel), a currently used therapeutic agent for melanoma, requires solvent system for solubilization, leading to poor chemical stability. Moreover, drug resistance often renders the drug inefficient in clinical setting. A novel β-cyclodextrin-modified gemini surfactant (CDgemini) delivery system was developed to incorporate Mel in order to improve its physicochemical and biological behavior. Melphalan nanoparticles (Mel-NP) showed optimal particle size in the 200-250 nm range for endocytosis and induced significantly higher cell death compared with Mel (50% of inhibitory concentration [IC₅₀] of 36 µM for the complexes vs 82 µM for Mel). The CDgemini delivery system did not alter the pathway of the cellular death triggered by Mel and caused no intrinsic toxicity to the cells. The Mel-NP complexes induced significant cell death in melanoma cells that were rendered resistant to Mel. These findings demonstrate in principle the applicability of the CDgemini delivery system as safe and efficient alternative to the current melanoma therapy, especially in chemoresistant cases.

Impact of phospholipids on plasmid packaging and toxicity of gemini nanoparticles

Understanding the relationship of structural modifications on the assembly and disassembly of synthetic or non-viral gene delivery is crucial with regard to their rational development. This study describes the use of fluorescence correlation spectroscopy (FCS), as a new tool, to investigate the effect of systematic chemical modifications to dicationic N,N-bis(dimethylalkyl)-α,ω-alkanediammonium surfactants (gemini surfactants) on the self-assembly and physical properties of a series of gemini nanoparticles (gemini NPs). A systematic screening of 27 gemini-plasmid (GP) complexes and gemini NPs showed that their final morphology is governed by the pre-compaction of plasmid by the gemini surfactants. The assembly process of gemini-plasmid intermediate complex (GP) and the final gemini NP (or gemini-plasmid-lipid complex, GPL) was monitored by the tracking of the Cy5-labeled plasmid. Based on diffusion properties, GP complexes were larger than gemini NPs (300-500 nm for GP and 200-300 nm for GPLs). Stoichiometric analysis of the raw intensity histograms showed that both GPs and GPLs particles were composed of multiple plasmids. The final GPLs contain fewer plasmids (2-20 per particle) compared to the intermediate GP (5-35 per particle). The addition of phospholipids dispersed and stabilized GPs to form GPL, but the type of phospholipid (DOPE or DD 1:3) had little effect on the final size of the particles. The FCS data were both validated and complemented by the results of studies of dynamic light scattering (DLS), atomic force microscopy (AFM), X-ray scattering and dye-exclusion assays. A model for gemini NP assembly involving supramolecular aggregate intermediates is proposed.

Characterization of the host-guest complex of a curcumin analog with β-cyclodextrin and β-cyclodextrin-gemini surfactant and evaluation of its anticancer activity

Background

Curcumin analogs, including the novel compound NC 2067, are potent cytotoxic agents that suffer from poor solubility, and hence, low bioavailability. Cyclodextrin-based carriers can be used to encapsulate such agents. In order to understand the interaction between the two molecules, the physicochemical properties of the host–guest complexes of NC 2067 with β-cyclodextrin (CD) or β-cyclodextrin–gemini surfactant (CDgemini surfactant) were investigated for the first time. Moreover, possible supramolecular structures were examined in order to aid the development of new drug delivery systems. Furthermore, the in vitro anticancer activity of the complex of NC 2067 with CDgemini surfactant nanoparticles was demonstrated in the A375 melanoma cell line.

Methods

Physicochemical properties of the complexes formed of NC 2067 with CD or CDgemini surfactant were investigated by synchrotron-based powder X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. Synchrotron-based small- and wide-angle X-ray scattering and size measurements were employed to assess the supramolecular morphology of the complex formed by NC 2067 with CDgemini surfactant. Lastly, the in vitro cell toxicity of the formulations toward A375 melanoma cells at various drug-to-carrier mole ratios were measured by cell viability assay.

Results

Physical mixtures of NC 2067 and CD or CDgemini surfactant showed characteristics of the individual components, whereas the complex of NC 2067 and CD or CDgemini surfactant presented new structural features, supporting the formation of the host–guest complexes. Complexes of NC 2067 with CDgemini surfactants formed nanoparticles having sizes of 100–200 nm. NC 2067 retained its anticancer activity in the complex with CDgemini surfactant for different drug-to-carrier mole ratios, with an IC₅₀ (half-maximal inhibitory concentration) value comparable to that for NC 2067 without the carrier.

Conclusion

The formation of host–guest complexes of NC 2067 with CD or CDgemini surfactant has been confirmed and hence the CDgemini surfactant shows good potential to be used as a delivery system for anticancer agents.

Advancing nonviral gene delivery: lipid- and surfactant-based nanoparticle design strategies

Gene therapy is a technique utilized to treat diseases caused by missing, defective or overexpressing genes. Although viral vectors transfect cells efficiently, risks associated with their use limit their clinical applications. Nonviral delivery systems are safer, easier to manufacture, more versatile and cost effective. However, their transfection efficiency lags behind that of viral vectors. Many groups have dedicated considerable effort to improve the efficiency of nonviral gene delivery systems and are investigating complexes composed of DNA and soft materials such as lipids, polymers, peptides, dendrimers and gemini surfactants. The bottom-up approach in the design of these nanoparticles combines components essential for high levels of transfection, biocompatibility and tissue-targeting ability. This article provides an overview of the strategies employed to improve in vitro and in vivo transfection, focusing on the use of cationic lipids and surfactants as building blocks for nonviral gene delivery systems.

Interactions between adsorbed layers of cationic gemini surfactants

The forces acting between glass and between mica surfaces in the presence of two cationic gemini surfactants, 1,4 diDDAB (1,4-butyl-bis(dimethyldodecylammonium bromide)) and 1,12 diDDAB (1,12-dodecyl-bis(dimethyldodecylammonium bromide)), have been investigated below the critical micelle concentration (cmc) of the surfactants using two different surface force techniques. In both cases, it was found that a recharging of the surfaces occurred at a surfactant concentration of about 0.1 x cmc, and at all surfactant concentrations investigated repulsive double-layer forces dominated the interaction at large separations. At smaller separations, attractive forces, or regions of separation with (close to) constant force, were observed. This was interpreted as being due to desorption and rearrangement in the adsorbed layer induced by the proximity of a second surface. Analysis of the decay length of the repulsive double-layer force showed that the majority of the gemini surfactants were fully dissociated. However, the degree of ion pair formation, between a gemini surfactant and a bromide counterion, increased with increasing surfactant concentration and was larger for the gemini surfactant with a shorter spacer length.

Topical non-invasive gene delivery using gemini nanoparticles in interferon-γ-deficient mice

Cutaneous gene therapy, although a promising approach for many dermatologic diseases, has not progressed to the stage of clinical trials, mainly due to the lack of an effective gene delivery system. The main objective of this study was to construct and evaluate gemini nanoparticles as a topical formulation for the interferon gamma (IFN-gamma) gene in an IFN-gamma-deficient mouse model. Nanoparticles based on the gemini surfactant 16-3-16 (NP16-DNA) and another cationic lipid cholesteryl 3beta-(-N-[dimethylamino-ethyl] carbamate) [Dc-chol] (NPDc-DNA) were prepared and characterized. Zetasizer measurement indicated a bimodal distribution of 146 and 468 nm average particle sizes for the NP16-DNA (zeta-potential +51 mV) nanoparticles and monomodal distribution of 625 nm (zeta-potential +44 mV) for the NPDc-DNA. Circular dichroism studies showed that the gemini surfactant compacted the plasmid more efficiently compared to the Dc-chol. Small-angle X-ray scattering measurements revealed structural polymorphism in the NP16-DNA nanoparticles, with lamellar and Fd3m cubic phases present, while for the NPDc-DNA two lamellar phases could be distinguished. In vivo, both topically applied nanoparticles induced higher gene expression compared to untreated control and naked DNA (means of 0.480 and 0.398 ng/cm(2) vs 0.067 and 0.167 ng/cm(2)). However, treatment with NPDc-DNA caused skin irritation, and skin damage, whereas NP16-DNA showed no skin toxicity. In this study, we demonstrated that topical cutaneous gene delivery using gemini surfactant-based nanoparticles in IFN-gamma-deficient mice was safe and may provide increased gene expression in the skin due to structural complexity of NP16 nanoparticles (lamellar-cubic phases).

In vivo cutaneous interferon-gamma gene delivery using novel dicationic (gemini) surfactant-plasmid complexes

BACKGROUND

Localized scleroderma (morphea and linear scleroderma) is a connective tissue disease, accompanied by excessive proliferation and deposition of collagen within the skin, inflammation, vasculopathy and a deranged immune system. Interferon gamma (IFNgamma), an inhibitor of collagen synthesis and an immunomodulator, could be a potential therapeutic agent if it could be delivered into or expressed locally in affected skin in a non-invasive manner. In this study, the feasibility of topical delivery of the IFNgamma gene and expression of IFNgamma were investigated in mice.

METHODS

Novel dicationic (gemini) surfactant (spacer length n=2-16; alkyl chain m=12 or 16)-DNA complexes were formulated and characterized by circular dichroism and atomic force microscopy to select gemini analogues with the highest transfection efficiency (TE). Transfection and cellular expression of IFNgamma from the bicistronic pGTmCMV.IFN-GFP plasmid were evaluated in PAM 212 keratinocyte culture by ELISA and fluorescence microscopy. Topical delivery of plasmid using liposomal and nanoemulsion systems, based on gemini surfactant 16-3-16, was evaluated in mice by IFNgamma expression analysis.

RESULTS

In vitro TE was found to be dependent on the spacer length of the gemini surfactant, with the C3 spacer showing the highest activity (both 12-3-12 and 16-3-16). Both gemini cationic liposomes and gemini nanoemulsion (3x25 microg DNA/animal) produced significantly higher levels of IFNgamma in the skin (359.4 and 607.24 pg/cm2) compared to naked DNA (135.69 pg/cm2) or a liposomal Dc-chol formulation (82.15 pg/cm2). IFNgamma expression in the lymph nodes was higher in the animals treated with gemini liposomes (422.74 pg/animal) compared to the nanoemulsion formulation (131.27 pg/animal) or the Dc-chol formulation (82pg/animal).

CONCLUSIONS

The feasibility of topical delivery of pGTmCMV.IFN-GFP plasmid in mice using gemini cationic surfactant based delivery systems was demonstrated. IFNgamma expression after treatment with gemini-DNA formulations in the skin was 3-5-fold higher compared to the treatment with naked DNA (p<0.05), and 4-6-fold higher than the Dc-chol-DNA complex, indicating a significant advance in topical DNA delivery across intact skin in vivo.

Effects of oral dosing with calcium propionate on total calcium and glucose concentrations in the plasma of the cow

This study aimed to determine the effect of oral drenching with molasses, calcium propionate and MgO on plasma glucose and calcium concentrations of dairy cows. Four trials were undertaken, each using three lactating and three non-lactating Jersey cows. In Trial 1, the effect of drenching with 200 ml molasses was measured. Trial 2 measured the effect of a single treatment with 349 g calcium propionate in 200 ml molasses. In Trial 3, the effect of 60 g MgO in molasses alone and in combination with calcium propionate was measured. Trial 4 tested the effect of repeating treatments with 349 g calcium propionate in 200 ml molasses 24 h apart. Dosing with 349 g calcium propionate in molasses increased plasma total calcium (Catot) concentration by 10% in lactating and non-lactating cows for periods less than 7 h, and this was not augmented by simultaneous administration of MgO or treatment 24 h earlier with 349 g calcium propionate in molasses. Treatment with 200 ml molasses alone resulted in increased plasma Catot of 7%. Plasma glucose concentrations were elevated by 11% for less than 3 h after treatment with calcium propionate. For the prevention of subclinical hypocalcaemia and ketosis in early lactation, drenching with calcium propionate solutions is unlikely to be of value due to the short duration of its effects, but the inclusion of calcium propionate in the postpartum ration deserves further investigation.

Rhodococcus equi--an increasingly recognized opportunistic pathogen. Report of 12 cases and review of 65 cases in the literature

Rhodococcus equi, a gram-positive, weakly acid-fast coccobacillus, initially isolated from horses, is becoming increasingly recognized as an important pathogen for immunosuppressed human hosts since the first human case was reported in 1967. A review of the English medical literature yielded 53 cases. During the last 11 years, the microbiology laboratories of the authors isolated the organism from 12 patients. Of the total 65 cases, 60 occurred in immunosuppressed patients with HIV infection, malignant neoplasms, or chronic immunosuppressive therapy. The lung is the most common primary site of infection. Typically, the lesion is densely infiltrated by histiocytes with multiple microabscesses. Intracellular gram-positive coccobacilli are easily demonstrated. R equi grows well on routine non-selective media at 35 degrees C. Previously, many cases may have been missed because the organism resembles oropharyngeal commensal diphtheroids. Clinical information with gram and Kinyoun strains on fresh isolates is helpful in recognizing the possibility of R equi infection.

The Streptococcus milleri group

The Streptococcus milleri group is newly recognized as a cause of pyogenic infection. It is important that microbiologists and physicians become aware of these organisms. The heterogeneous nature of this group of streptococci does mean that laboratories will have to use a combination of antigenic, physiologic, and hemolytic characteristics to identify these pathogenic streptococci. Physicians need to recognize that these microorganisms as a group are able to cause serious infections that may require prolonged treatment and/or surgical drainage of abscesses.

Serratia marcescens

Serratia marcescens is now recognized as a serious pathogen and of particular importance in nosocomial infections. Both hand-to-hand and point-source transmission can result in outbreaks. The organism is easily grown and identified in the microbiology laboratory. Treatment may be difficult due to plasmid-mediated resistance. Typing systems are available and can be useful for epidemiologic studies.