Solid lipid nanoparticles can effectively bind DNA, streptavidin and biotinylated ligands

Solid lipid nanoparticles: a versatile approach for controlled release and targeted drug delivery

Solid Lipid Nanoparticles (SLN), the first type of lipid-based solid carrier systems in the nanometer range, were introduced as a replacement for liposomes. SLN are aqueous colloidal dispersions with solid biodegradable lipids as their matrix. SLN is produced using processes like solvent diffusion method and high-pressure homogenization, among others. Major benefits include regulated release, increased bioavailability, preservation of peptides and chemically labile compounds like retinol against degradation, cost-effective excipients, better drug integration, and a broad range of applications. Solid lipid nanoparticles can be administered via different routes, such as oral, parenteral, pulmonary, etc. SLN can be prepared by using high shear mixing as well as low shear mixing. The next generation of solid lipids, nanostructured lipid carriers (NLC), can reduce some of the drawbacks of SLN, such as its restricted capacity for drug loading and drug expulsion during storage. NLC are controlled nanostructured lipid particles that enhance drug loading. This review covers a brief introduction of solid lipid nanoparticles, manufacturing techniques, benefits, limitations, and their characterization tests.

Dually Modified Cellulose as a Non-Viral Vector for the Delivery and Uptake of HDAC3 siRNA

RNA interference can be applied to different target genes for treating a variety of diseases, but an appropriate delivery system is necessary to ensure the transport of intact siRNAs to the site of action. In this study, cellulose was dually modified to create a non-viral vector for HDAC3 short interfering RNA (siRNA) transfer into cells. A guanidinium group introduced positive charges into the cellulose to allow complexation of negatively charged genetic material. Furthermore, a biotin group fixed by a polyethylene glycol (PEG) spacer was attached to the polymer to allow, if required, the binding of targeting ligands. The resulting polyplexes with HDAC3 siRNA had a size below 200 nm and a positive zeta potential of up to 15 mV. For N/P ratio 2 and higher, the polymer could efficiently complex siRNA. Nanoparticles, based on this dually modified derivative, revealed a low cytotoxicity. Only minor effects on the endothelial barrier integrity and a transfection efficiency in HEK293 cells higher than Lipofectamine 2000TM were found. The uptake and release of the polyplexes were confirmed by immunofluorescence imaging. This study indicates that the modified biopolymer is an auspicious biocompatible non-viral vector with biotin as a promising moiety.

Solid Lipid Nanoparticles: Applications and Prospects in Cancer Treatment

Recent advancements in drug delivery technologies paved a way for improving cancer therapeutics. Nanotechnology emerged as a potential tool in the field of drug delivery, overcoming the challenges of conventional drug delivery systems. In the field of nanotechnology, solid lipid nanoparticles (SLNs) play a vital role with a wide range of diverse applications, namely drug delivery, clinical medicine, and cancer therapeutics. SLNs establish a significant role owing to their ability to encapsulate hydrophilic and hydrophobic compounds, biocompatibility, ease of surface modification, scale-up feasibility, and possibilities of both active and passive targeting to various organs. In cancer therapy, SLNs have emerged as imminent nanocarriers for overcoming physiological barriers and multidrug resistance pathways. However, there is a need for special attention to be paid to further improving the conceptual understanding of the biological responses of SLNs in cancer therapeutics. Hence, further research exploration needs to be focused on the determination of the structure and strength of SLNs at the cellular level, both in vitro and in vivo, to develop potential therapeutics with reduced side effects. The present review addresses the various modalities of SLN development, SLN mechanisms in cancer therapeutics, and the scale-up potential and regulatory considerations of SLN technology. The review extensively focuses on the applications of SLNs in cancer treatment.

Physicochemical and biopharmaceutical aspects influencing skin permeation and role of SLN and NLC for skin drug delivery

The skin is a complex and multifunctional organ, in which the static versus dynamic balance is responsible for its constant adaptation to variations in the external environment that is continuously exposed. One of the most important functions of the skin is its ability to act as a protective barrier, against the entry of foreign substances and against the excessive loss of endogenous material. Human skin imposes physical, chemical and biological limitations on all types of permeating agents that can cross the epithelial barrier. For a molecule to be passively permeated through the skin, it must have properties, such as dimensions, molecular weight, pKa and hydrophilic-lipophilic gradient, appropriate to the anatomy and physiology of the skin. These requirements have limited the number of commercially available products for dermal and transdermal administration of drugs. To understand the mechanisms involved in the drug permeation process through the skin, the approach should be multidisciplinary in order to overcome biological and pharmacotechnical barriers. The study of the mechanisms involved in the permeation process, and the ways to control it, can make this route of drug administration cease to be a constant promise and become a reality. In this work, we address the physicochemical and biopharmaceutical aspects encountered in the pathway of drugs through the skin, and the potential added value of using solid lipid nanoparticles (SLN) and nanostructured lipid vectors (NLC) to drug permeation/penetration through this route. The technology and architecture for obtaining lipid nanoparticles are described in detail, namely the composition, production methods and the ability to release pharmacologically active substances, as well as the application of these systems in the vectorization of various pharmacologically active substances for dermal and transdermal applications. The characteristics of these systems in terms of dermal application are addressed, such as biocompatibility, occlusion, hydration, emollience and the penetration of pharmacologically active substances. The advantages of using these systems over conventional formulations are described and explored from a pharmaceutical point of view.

Magnetic resonance colonography with intestine-absorbable nanoparticle contrast agents in evaluation of colorectal inflammation

OBJECTIVES

To develop a nanoparticle-based MRI protocol based on transrectal administration of intestine-absorbable nanoparticle contrast agents to evaluate ulcerative colitis (UC).

METHODS

Solid lipid nanoparticles (SLNs) were synthesized by loading gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) and octadecylamine-fluorescein isothiocyanate to produce Gd-FITC-SLNs as T1 contrast agents. Twenty mice with acute UC were divided into four groups: enema with Gd-FITC-SLNs, intravenous injection of Gd-FITC-SLNs, enema with Gd-DTPA, and intravenous injection of Gd-DTPA. Five mice with chronic UC and five mice without UC underwent enema with Gd-FITC-SLNs. Axial T1- and T2-weighted MR images were obtained before and 20, 40, 60, 80,100, and 120 min after enema or intravenous injection of the contrast agent. The signal-to-noise ratios (SNRs) of the colorectal wall were measured in both groups. The MRI findings were correlated with subsequent histological confirmation.

RESULTS

At 20 min after enema with Gd-FITC-SLNs, MRI showed the following contrast enhancement pattern: acute UC > normal intestinal wall > chronic UC. A continuous enhancement effect was observed in mice with acute UC, whereas a slight continuous enhancement of the colorectal wall was observed in mice with chronic UC. The normal intestinal wall rapidly metabolized the contrast agent, and the enhancement decreased on sequential scans. There was no significant difference between the SNRs of the intestinal wall at 20 min after intravenous Gd-DTPA and transrectal Gd-FITC-SLN administration.

CONCLUSIONS

Enema with Gd-FITC-SLNs may be helpful for the diagnosis and differential diagnosis of acute and chronic UC and can confer the same or better results than with intravenous Gd-DTPA.

KEY POINTS

• Enema with Gd-FITC-SLNs may be helpful for the diagnosis and differential diagnosis of acute and chronic UC. • Enema with Gd-FITC-SLNs can achieve the same or better result than that with intravenous Gd-DTPA. • SLN-based MR colonography enhances the colorectal wall inflammation, based on the colonic absorption of the nanoparticle contrast agents.

Nanotechnology to improve the Alzheimer's disease therapy with natural compounds

Alzheimer's disease (AD) is a form of dementia with high impact worldwide, accounting with more than 46 million cases. It is estimated that the number of patients will be four times higher in 2050. The initial symptoms of AD are almost imperceptible and typically involve lapses of memory in recent events. However, the available medicines still focus on controlling the symptoms and do not cure the disease. Regarding the advances in the discovery of new treatments for this devastating disease, natural compounds are gaining increasing relevance in the treatment of AD. Nevertheless, they present some limiting characteristics such as the low bioavailability and the low ability to cross the blood-brain barrier (BBB) that hinder the development of effective therapies. To overcome these issues, the delivery of natural products by targeting nanocarriers has aroused a great interest, improving the therapeutic activity of these molecules. In this article, a review of the research progress on drug delivery systems (DDS) to improve the therapeutic activity of natural compounds with neuroprotective effects for AD is presented. Graphical abstract.

Perillaldehyde 1,2-epoxide Loaded SLN-Tailored mAb: Production, Physicochemical Characterization and In Vitro Cytotoxicity Profile in MCF-7 Cell Lines

We have developed a new cationic solid lipid nanoparticle (SLN) formulation, composed of Compritol ATO 888, poloxamer 188 and cetyltrimethylammonium bromide (CTAB), to load perillaldehyde 1,2-epoxide, and surface-tailored with a monoclonal antibody for site-specific targeting of human epithelial growth receptor 2 (HER2). Perillaldehyde 1,2-epoxide-loaded cationic SLN (cPa-SLN), with a mean particle size (z-Ave) of 275.31 ± 4.78 nm and polydispersity index (PI) of 0.303 ± 0.081, were produced by high shear homogenization. An encapsulation efficiency of cPa-SLN above 80% was achieved. The release of perillaldehyde 1,2-epoxide from cationic SLN followed the Korsemeyer-Peppas kinetic model, which is typically seen in nanoparticle formulations. The lipid peroxidation of cPa-SLN was assessed by the capacity to produce thiobarbituric acid-reactive substances, while the antioxidant activity was determined by the capacity to scavenge the stable radical DPPH. The surface functionalization of cPa-SLN with the antibody was done via streptavidin-biotin interaction, monitoring z-Ave, PI and ZP of the obtained assembly (cPa-SLN-S_Ab), as well as its stability in phosphate buffer. The effect of plain cationic SLN (c-SLN, monoterpene free), cPa-SLN and cPa-SLN-S_Ab onto the MCF-7 cell lines was evaluated in a concentration range from 0.01 to 0.1 mg/mL, confirming that streptavidin adsorption onto cPa-SLN-S_Ab improved the cell viability in comparison to the cationic cPa-SLN.

Deliverable transgenics & gene therapy possibilities for the testes

Male infertility and hypogonadism are clinically prevalent conditions with a high socioeconomic burden and are both linked to an increased risk in cardiovascular-metabolic diseases and earlier mortality. Therefore, there is an urgent need to better understand the causes and develop new treatments for these conditions that affect millions of men. The accelerating advancement in gene editing and delivery technologies promises improvements in both diagnosis as well as affording the opportunity to develop bespoke treatment options which would both prove beneficial for the millions of individuals afflicted with these reproductive disorders. In this review, we summarise the systems developed and utilised for the delivery of gene therapy and discuss how each of these systems could be applied for the development of a gene therapy system in the testis and how they could be of use for the future diagnosis and repair of common male reproductive disorders.

Topical delivery of TRPsiRNA-loaded solid lipid nanoparticles confer reduced pain sensation via TRPV1 silencing, in rats

Present work describes a novel composition for encapsulating TRPsiRNA (TRPV1-targeting siRNA) within lipid-matrix (4:1::glyceryl behnate:stearic acid) of SLNs, using suitably modified cold high-pressure homogenisation technique. Optimisation of the method and composition conducted using calf-thymus DNA (ctDNA), to avoid cost of TRPsiRNA molecules, resulted in small size (d₅₀ = 50-100 nm) and high entrapment (77.22-98.5%). Complete masking of extreme negative charge of both ctDNA (-34.50 mV) and TRPsiRNA (-23.98 mV) upon encapsulation in SLNs without employing cationic components is reported herein for the first time. Diffusion-controlled release (90.17% at 72 h) from a rigid matrix shifted to porous matrix (at 24 h) due to solubilisation of stearic acid at 37 °C. Efficient in vitro (HEK293 T cells) and in vivo transfection and expression established the proof-of-concept. PEG600 as supporting-surfactant and vitrifying agent promoted small size, effective transfection and rupture of endosomal membrane to affect endosomal escape. Physiological efficacy in terms of significant increase (p < .0001) in paw-withdrawal-latency, following topical and intradermal application of TRPsiRNA-loaded SLNs, in rats, exposed to thermal hyperalgesia (145 and 182%, respectively) and capsaicin-induced pain (155 and 182%, respectively) indicate effective silencing of skin TRPV1. Significant decrease in intensity and duration (one-fifth) of capsaicin-induced nocifensive behaviour was also observed. Naked TRPsiRNA, however, did not show any effect.

Docetaxel‐loaded solid lipid nanoparticles: a novel drug delivery system

Over the past few years, taxanes have emerged as a new class of anticancer drugs. Docetaxel (DTX) the prototype of this class has been approved for the treatment of broad range of cancers. However, to date the commercial preparation of DTX (Taxotere^®) is accompanying adverse side effects, intolerance, and poor solubility, which can be overcome by encapsulating them using solid lipid nanoparticles (SLNs). SLNs represent versatile delivery system of drugs with newer forms such as polymer–solid lipid hybrid, surface modified and long circulating nanoparticles bringing forth improved prospects for cancer chemotherapy. In this review, the authors have discussed the current uses of various SLNs formulations of DTX with key emphasis on controlled and site‐specific drug delivery along with enhanced antitumour activity elucidated via in vitro and in vivo studies. Furthermore, the review article highlights few approaches that can be used in combination with existing DTX‐loaded SLNs to supplement DTX drug delivery.

Improved immunogenicity of Newcastle disease virus inactivated vaccine following DNA vaccination using Newcastle disease virus hemagglutinin-neuraminidase and fusion protein genes

The present study describes the development of DNA vaccines using the hemagglutinin-neuraminidase (HN) and fusion (F) genes from AF2240 Newcastle disease virus strain, namely pIRES/HN, pIRES/F and pIRES-F/HN. Transient expression analysis of the constructs in Vero cells revealed the successful expression of gene inserts in vitro. Moreover, in vivo experiments showed that single vaccination with the constructed plasmid DNA (pDNA) followed by a boost with inactivated vaccine induced a significant difference in enzyme-linked immunosorbent assay antibody levels (p < 0.05) elicited by either pIRES/F, pIRES/F+ pIRES/HN or pIRES-F/HN at one week after the booster in specific pathogen free chickens when compared with the inactivated vaccine alone. Taken together, these results indicated that recombinant pDNA could be used to increase the efficacy of the inactivated vaccine immunization procedure.

Nanocarriers: a versatile approach for mucosal vaccine delivery

Infectious agents generally use mucosal surfaces as entry port to the body thereby necessitating the need of development of mucosal vaccine as vaccination is important for disease avoidance and suppression. Vaccination through mucosal route is a promising strategy to elicit efficient immune response as parentally administered vaccines induce poor mucosal immunity in general. Safety, economy and stability are highly desired with vaccines and this can be achieved with use of delivery cargos. This review focuses on challenges related with mucosal vaccines and use of nanocarriers as suitable cargos to cater the antigen effectively to the desired site. The review also includes different factors which are to be considered regarding the performance of the nanocarriers and clinical status of these systems.

Analysis of the structure of nanocomposites of triglyceride platelets and DNA

DNA-complexes with platelet-like, cationically modified lipid nanoparticles (cLNPs) are studied with regard to the formation of nanocomposite structures with a sandwich-like arrangement of the DNA and platelets.

Lipid nanoparticles as carriers for RNAi against viral infections: current status and future perspectives

The efforts made to develop RNAi-based therapies have led to productive research in the field of infections in humans, such as hepatitis C virus (HCV), hepatitis B virus (HBV), human immunodeficiency virus (HIV), human cytomegalovirus (HCMV), herpetic keratitis, human papillomavirus, or influenza virus. Naked RNAi molecules are rapidly digested by nucleases in the serum, and due to their negative surface charge, entry into the cell cytoplasm is also hampered, which makes necessary the use of delivery systems to exploit the full potential of RNAi therapeutics. Lipid nanoparticles (LNP) represent one of the most widely used delivery systems for in vivo application of RNAi due to their relative safety and simplicity of production, joint with the enhanced payload and protection of encapsulated RNAs. Moreover, LNP may be functionalized to reach target cells, and they may be used to combine RNAi molecules with conventional drug substances to reduce resistance or improve efficiency. This review features the current application of LNP in RNAi mediated therapy against viral infections and aims to explore possible future lines of action in this field.

DNA delivery via cationic solid lipid nanoparticles (SLNs)

In recent years the use of solid lipid nanoparticles (SLNs) as transport systems for the delivery of drugs and biomolecules has become particularly important. The use of cationic SLNs developed by the technique of microemulsion, which are complexed with DNA in order to study their application as non-viral vectors in gene therapy, is reported. The nanoparticles are characterized by scanning electron microscopy and transmission electron microscopy (SEM and TEM), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). Furthermore, the process of lyophilization of the samples and their stability was studied. The nanoparticles obtained presented a particle size of 340 nm with a positive surface charge of 44 mV and the capability of forming lipoplexes with DNA plasmids was stated.

Cellular delivery of cationic lipid nanoparticle-based SMAD3 antisense oligonucleotides for the inhibition of collagen production in keloid fibroblasts

SMAD3 is a key player in the TGFβ signaling pathway as a primary inducer of fibrosis. The inhibition of SMAD3 production is one strategy to alleviate fibrosis in keloid fibroblasts. In the present study, antisense oligonucleotides (ASOs) against SMAD3 were designed to specifically block the expression of SMAD3. The cationic lipid nanoparticles (cLNs) were formulated to enhance an intracellular activity of SMAD3 ASOs in keloid fibroblasts. This formulation was prepared using melt-homogenization method, composed of 3-[N-(N',N'-dimethylaminoethane)-carbamol] cholesterol (DC-Chol), dioleoylphosphatidylethanolamine (DOPE), Tween20, and trimyristin as a lipid core (1:1:1:1.3, w/w). The size and zeta potential of cLNs and cLN/ASO complexes were measured using light scattering. AFM was used to confirm the morphology and the size distribution of cLNs and cLN/ASO complexes. The prepared cLNs had a nano-scale sized spherical shape with highly positive charge, which were physically stable without aggregation during the storage. The cLN/SMAD3 ASO complexes were successfully generated and internalized onto keloid fibroblasts without toxicity. After the treatment with cLN/ASO complexes, SMAD3 was inhibited and collagen type I was also significantly suppressed in keloid fibroblasts. These results suggest that SMAD3 ASOs complexed with cLNs have a therapeutic potential to suppress collagen deposition in fibrotic diseases. Therefore, this strategy might be developed to lead to anti-fibrotic therapies.

Preparation and optimization of PIT solid lipid nanoparticles via statistical factorial design

The objective of this study was the preparation, physico-chemical characterization and statistical optimization of cationic solid lipid nanoparticles (SLN) prepared by the PIT method as potential carrier for gene therapy, emphasizing the application of factorial design in such a kind of studies. The preliminary screening from a physico-chemical point of view on three cationic lipids (CTAB, DDAB and DOTAP), selected on the basis of their different chemical structure and increasing lipophilicity, allowed us to select SLN with DOTAP, due to its higher zeta potential and smaller particle size. Afterward, a 2(2) full factorial experimental design was developed in order to study the effects of two independent variables (amount of DOTAP and concentration of lipid matrix) and their interaction on mean particle size and zeta potential values. The factorial planning was validated by ANOVA analysis; the correspondence between the predicted values of size and zeta and those measured experimentally confirmed the validity of the design and the equation applied for its resolution. The factorial design showed a significant influence of the independent variables on the selected parameters; in particular, a higher effect of DOTAP was observed on zeta potential value. Different dilutions of the optimized SLN containing 7% w/w of cutina CP and 1% w/w of DOTAP, with size and zeta potential values respectively of 462.9 nm and 50.8 mV, were in vitro examined to evaluate the possible cytotoxicity on two models of cell cultures: human prostate cancer androgen-non-responsive DU-145 cells and primary cultures of rat astrocytes.

In vivo sustained release of siRNA from solid lipid nanoparticles

Small interfering RNA (siRNA) is a highly potent drug in gene-based therapy with a challenge of being delivered in a sustained manner. Nanoparticle drug delivery systems allow for incorporating and controlled release of therapeutic payloads. We demonstrate that solid lipid nanoparticles can incorporate and provide sustained release of siRNA. Tristearin solid lipid nanoparticles, made by nanoprecipitation, were loaded with siRNA (4.4-5.5 wt % loading ratio) using a hydrophobic ion pairing approach that employs the cationic lipid DOTAP. Intradermal injection of these nanocarriers in mouse footpads resulted in prolonged siRNA release over a period of 10-13 days. In vitro cell studies showed that the released siRNA retained its activity. Nanoparticles developed in this study offer an alternative approach to polymeric nanoparticles for encapsulation and sustained delivery of siRNA with the advantage of being prepared from physiologically well-tolerated materials.

The role of protamine amount in the transfection performance of cationic SLN designed as a gene nanocarrier

Cationic solid lipid nanoparticles (SLN) have been recently proposed as non-viral vectors in systemic gene therapy. The aim of this study was to evaluate the effect of the protamine amount used as the transfection promoter in SLN-mediated gene delivery. Three protamine-SLN samples (Pro25, Pro100, and Pro200) prepared by adding increasing amounts of protamine were characterized for their size, zeta potential, and protamine loading level. The samples were evaluated for pDNA complexation ability by gel-electrophoresis analysis and for cytotoxicity and transfection efficiency by using different cell lines (COS-I, HepG2, and Na1300). The size of SLN was ~230 nm and only Pro200 showed few particle aggregates. Unlike the Pro25 sample with the lowest protamine loading level, the others SLN samples (Pro100 and Pro200) exhibited a good ability in complexing pDNA. A cell-line dependent cytotoxicity lower than that of the positive control PEI (polyethilenimmine) was observed for all the SLN. Among these, only Pro100, having an intermediate amount of protamine, appeared able to promote pDNA cell transfer, especially in a neuronal cell line (Na1300). In conclusion, the amount of protamine as the transfection promoter in SLN affects not only the gene delivery ability of SLN but also their capacity to transfer genes efficiently to specific cell types.

Structural investigation and intracellular trafficking of a novel multicomposite cationic solid lipid nanoparticle platform as a pDNA carrier

Background: The ability to efficiently cross cellular barriers and accomplish high-level transgene expression is a critical challenge to broad application of nonviral vectors, such as cationic solid lipid nanoparticles (SLN). Aims: This study aims to design and characterize in vitro multicomposite SLN as a novel platform for pDNA delivery. Results/Discussion: The distribution of each component (stearic acid, stearylamine, phosphatidylcholine, cholesterol, protamine and Pluronic F68) in the SLN matrix was studied by electron spectroscopy for chemical analysis and NMR in order to establish its influence on SLN cytotoxicity and transfection efficiency. Multicomposite SLN mediated the expression of enhanced green fluorescent protein in a way comparable with the positive control, but inducing a lower cytotoxicity. Moreover, the carrier exhibited the ability to enter the nucleoli, probably as a result of the synergic action of the nuclear localization signal of protamine and the flexibility of the lipid matrix owing to the phosphatidylcholine. Conclusion: The multicomposite SLN showed good transfection efficiency and negligible cytotoxicity, both crucial factors for an efficient gene-delivery system. Considering the fact that nucleoli have emerged in recent years as important targets in many fields, this novel carrier could have significant future therapy involvements whenever there is a requirement to overcome subcellular barriers. However, further work needs to be carried out in order to fully characterize the formulation, to elucidate where alternative colloidal structures might exist and play a role in obtaining the results presented.

Effects of poly(lactic-co-glycolic acid) on preparation and characteristics of plasmid DNA-loaded solid lipid nanoparticles

Poly(lactic-co-glycolic acid) (PLGA) was used as a polymeric emulsifier to encapsulate plasmid DNA into hydrogenated castor oil (HCO)-solid lipid nanoparticles (SLN) by w/o/w double emulsion and solvent evaporation techniques. The effects of PLGA on the preparation, characteristics and transfection efficiency of DNA-loaded SLN were studied. The results showed that PLGA was essential to form the primary w/o emulsion and the stability of the emulsion was enhanced with the increase of PLGA content. DNA-loaded SLN were spherical with smooth surfaces. The SLN had a negative charge in weak acid and alkaline environment but acquired a positive charge in acidic pH and the cationisation capacity of the SLN increased with the increase of PLGA/HCO ratio. Agarose gel electrophoresis demonstrated that the majority of the DNA maintained its structural integrity after preparation and being extracted or released from DNA-loaded SLN. When PLGA/HCO ratio increased from 5 to 15%, the encapsulation efficiency, loading capacity and transfection efficiency of the nanoparticles increased significantly, whereas the changes of particle size and polydispersity index were insignificant. Cytotoxicity study in cell culture demonstrated that the SLN was not toxic.

Nanocarrier possibilities for functional targeting of bioactive peptides and proteins: state-of-the-art

This review attempts to provide an updated compilation of studies reported in the literature pertaining to production of nanocarriers encasing peptides and/or proteins, in a way that helps the reader direct a bibliographic search and develop an integrated perspective of the subject. Highlights are given to bioactive proteins and peptides, with a special focus on those from dairy sources (including physicochemical characteristics and properties, and biopharmaceutical application possibilities of e.g. lactoferrin and glycomacropeptide), as well as to nanocarrier functional targeting. Features associated with micro- and (multiple) nanoemulsions, micellar systems, liposomes and solid lipid nanoparticles, together with biopharmaceutical considerations, are presented in the text in a systematic fashion.

Influence of phospholipid composition on cationic emulsions/DNA complexes: physicochemical properties, cytotoxicity, and transfection on Hep G2 cells

BACKGROUND

Cationic nanoemulsions have been recently considered as potential delivery systems for nucleic acids. This study reports the influence of phospholipids on the properties of cationic nanoemulsions/DNA plasmid complexes.

METHODS

Nanoemulsions composed of medium-chain triglycerides, stearylamine, egg lecithin or isolated phospholipids, ie, DSPC, DOPC, DSPE, or DOPE, glycerol, and water were prepared by spontaneous emulsification. Gene transfer to Hep G2 cells was analyzed using real-time polymerase chain reaction.

RESULTS

The procedure resulted in monodispersed nanoemulsions with a droplet size and zeta potential of approximately 250 nm and +50 mV, respectively. The complexation of cationic nanoemulsions with DNA plasmid, analyzed by agarose gel retardation assay, was complete when the complex was obtained at a charge ratio of ≥ 1.0. In these conditions, the complexes were protected from enzymatic degradation by DNase I. The cytotoxicity of the complexes in Hep G2 cells, evaluated by MTT assay, showed that an increasing number of complexes led to progressive toxicity. Higher amounts of reporter DNA were detected for the formulation obtained with the DSPC phospholipid. Complexes containing DSPC and DSPE phospholipids, which have high phase transition temperatures, were less toxic in comparison with the formulations obtained with lecithin, DOPC, and DOPE.

CONCLUSION

The results show the effect of the DNA/nanoemulsion complexes composition on the toxicity and transfection results.

Solid lipid nanoparticles loaded with anti-microRNA oligonucleotides (AMOs) for suppression of microRNA-21 functions in human lung cancer cells

PURPOSE

Literature has highlighted the practical use of solid lipid nanoparticles (SLNs) in research, but few reports have combined SLNs with miRNA-based therapy. We aimed to prepare SLNs to load anti-miRNA oligonucleotide (AMO) for miRNA-based therapy in vitro.

METHODS

SLNs were employed to encapsulate AMO by a solvent diffusion method, and then the properties of AMO-CLOSs (cationic lipid binded oligonucleotide (AMO)-loaded SLNs) were characterized. We studied cellular uptake and activation properties of AMO-CLOSs in A549 cells, including antisense efficiency, cell migration and invasion.

RESULTS

AMO-CLOSs were 187 nm in size and 46.6 mV in zeta potential with an approximately toroid morphology in the TEM image. AMO-CLOSs uptake by A549 cells was increased significantly higher and more effective than free AMO. Further results demonstrated that AMO-CLOSs showed high antisense efficiency of microRNA-21 and subsequently decreased the proliferation, migration and invasion of tumor cells.

CONCLUSIONS

These findings suggest that AMO-CLOSs represent a potential new approach for carrying anti-miRNA inhibitors for cancer therapy.

Novel method to label solid lipid nanoparticles with 64cu for positron emission tomography imaging

Solid lipid nanoparticles (SLNs) are submicrometer (1-1000 nm) colloidal carriers developed in the past decade as an alternative system to traditional carriers (emulsions, liposomes, and polymeric nanoparticles) for intravenous applications. Because of their potential as drug carriers, there is much interest in understanding the in vivo biodistribution of SLNs following intravenous (i.v.) injection. Positron emission tomography (PET) is an attractive method for investigating biodistribution but requires a radiolabeled compound. In this work, we describe a method to radiolabel SLN for in vivo PET studies. A copper specific chelator, 6-[p-(bromoacetamido)benzyl]-1,4,8,11-tetraazacyclotetradecane-N,N',N'',N'''-tetraacetic acid (BAT), conjugated with a synthetic lipid, was incorporated into the SLN. Following incubation with (64)CuCl(2) for 1 h at 25 °C in 0.1 M NH(4)OAc buffer (pH 5.5), the SLNs (∼150 nm) were successfully radiolabeled with (64)Cu (66.5% radiolabeling yield), exhibiting >95% radiolabeled particles following purification. The (64)Cu-SLNs were delivered intravenously to mice and imaged with PET at 0.5, 3, 20, and 48 h post injection. Gamma counting was utilized post imaging to confirm organ distributions. Tissue radioactivity (% injected dose/gram, %ID/g), obtained by quantitative analysis of the images, suggests that the (64)Cu-SLNs are circulating in the bloodstream after 3 h (blood half-life ∼1.4 h), but are almost entirely cleared by 48 h. PET and gamma counting demonstrate that approximately 5-7%ID/g (64)Cu-SLNs remain in the liver at 48 h post injection. Stability assays confirm that copper remains associated with the SLN over the 48 h time period and that the biodistribution patterns observed are not from free, dissociated copper. Our results indicate that SLNs can be radiolabeled with (64)Cu, and their biodistribution can be quantitatively evaluated by in vivo PET imaging and ex vivo gamma counting.

Development of nanoparticle-based magnetic resonance colonography

This study was to develop a novel method of nanoparticle-based MR colonography. Two types of solid lipid nanoparticles (SLNs) were synthesized with loading of (a) gadolinium (Gd) diethylenetriaminepenta acetic acid to construct Gd-SLNs as an MR T1 contrast agent and (b) otcadecylamine-fluorescein-isothiocyanate to construct Gd-fluorescein isothiocyanate (FITC)-SLNs for histologic confirmation of MR findings. Through an in vitro experiment, we first evaluated the size distribution and gadolinium diethylenetriaminepenta acetic acid entrapment efficiency of these SLNs. The SLNs displayed a size distribution of 50-300 nm and a gadolinium diethylenetriaminepenta acetic acid entrapment efficiency of 56%. For in vivo validation, 30 mice were divided into five groups, each of which was administered a transrectal enema using: (i) Gd-SLNs (n=6); (ii) Gd-FITC-SLNs (n=6); (iii) blank SLNs (n=6); (iv) gadolinium diethylenetriaminepenta acetic acid (n=6); and (v) water (n=6). T1-weighted fluid-attenuated inversion-recovery MRI was then performed on mice after transrectal infusion of Gd-SLNs or Gd-FITC-SLNs, which demonstrated bright enhancement of the colonic walls, with decrease in T1 relaxation time. When Gd-FITC-SLNs were delivered, green fluorescent spots were visualized in both the extracelluar space and the cytoplasm through colonic walls under confocal microscopy and fluorescence microscopy. This study establishes the "proof-of-principle" of a new imaging technique, called "nanoparticle-based MR colonography," which may provide a useful imaging tool for the diagnosis of colorectal diseases.

Solid lipid nanoparticles: a modern formulation approach in drug delivery system

Solid lipid nanoparticles are at the forefront of the rapidly developing field of nanotechnology with several potential applications in drug delivery, clinical medicine and research, as well as in other varied sciences. Due to their unique size-dependent properties, lipid nanoparticles offer the possibility to develop new therapeutics. The ability to incorporate drugs into nanocarriers offers a new prototype in drug delivery that could be used for secondary and tertiary levels of drug targeting. Hence, solid lipid nanoparticles hold great promise for reaching the goal of controlled and site specific drug delivery and hence have attracted wide attention of researchers. This review presents a broad treatment of solid lipid nanoparticles discussing their advantages, limitations and their possible remedies. The different types of nanocarriers which were based on solid lipid like solid lipid nanoparticles, nanostructured lipid carriers, lipid drug conjugates are discussed with their structural differences. Different production methods which are suitable for large scale production and applications of solid lipid nanoparticles are described. Appropriate analytical techniques for characterization of solid lipid nanoparticles like photon correlation spectroscopy, scanning electron microscopy, differential scanning calorimetry are highlighted. Aspects of solid lipid nanoparticles route of administration and their biodistribution are also incorporated. If appropriately investigated, solid lipid nanoparticles may open new vistas in therapy of complex diseases.

Novel cationic SLN containing a synthesized single-tailed lipid as a modifier for gene delivery

Cationic solid lipid nanoparticles (SLN) can bind DNA directly via ionic interaction and mediate in vitro gene transfection. However, toxicity is still an obstacle, which is strongly dependent on the cationic lipid used. In the present study, a novel single-tailed cationic lipid, 6-lauroxyhexyl lysinate (LHLN), was synthesized and used as a modifier to prepare stable SLN-DNA complexes by a nanoprecipitation method. The commonly used cationic lipid cetyltrimethylammonium bromide (CTAB) modified SLN-DNA formulation served as a contrast. These two formulations were characterized and compared in terms of morphology, particle size, surface charge, DNA binding capacity, release profile, cytotoxicity, and transfection efficiency. The LHLN SLN-DNA complexes had a similar spherical morphology, a relatively narrow particle size distribution and a more remarkable DNA loading capability compared to the CTAB ones. Most importantly, LHLN modified SLN had a higher gene transfection efficiency than the naked DNA and CTAB ones, which was approximately equal to that of Lipofectamine-DNA complexes, and a lower cytotoxicity compared with CTAB-SLN and Lipofectamine 2000. Thus, the novel cationic SLN can achieve efficient transfection of plasmid DNA, and to some extent reduce the cytotoxicity, which might overcome some drawbacks of the conventional cationic nanocarriers in vivo and may become a promising non-viral gene therapy vector.

Protamine sulfate/poly(L-aspartic acid) polyionic complexes self-assembled via electrostatic attractions for combined delivery of drug and gene

In this study, a series of self-assembled polyionic complexes (PICs) were prepared via electrostatic attraction between protamine sulfate (PS) and poly(L-aspartic acid) (PASP) or doxorubicin (DOX)-conjugated PASP (DOX-PASP). The size of the PICs measured by Nano-ZS ZEN3600 was around 200-300 nm at different weight ratios of PS/PASP. Transmission electron microscopy (TEM) showed that PS/PASP PICs displayed a regular spherical shape and no aggregation was observed. The cytotoxicity study indicated that the PICs did not exhibit apparent cytotoxicity in comparison with that of 25 kDa polyethylenimine (PEI). Gel retardation assay indicated that the PICs were able to bind DNA completely when weight ratio of PS/PASP was higher than 2:1. Luciferase assay and green fluorescent protein (GFP) detection were used to confirm that the PICs could be used as efficient non-viral gene vectors and they exhibited comparable transfection efficiency with the one of 25 kDa PEI. Furthermore, confocal laser scanning microscopy as well as suppression activity of DOX-conjugated PICs (DOX-PICs) showed that they could quickly release the loaded DOX into HeLa cells, indicating that PICs can be also used as carriers for combined delivery of drug and gene.

Progress in developing cationic vectors for non-viral systemic gene therapy against cancer

Initially, gene therapy was viewed as an approach for treating hereditary diseases, but its potential role in the treatment of acquired diseases such as cancer is now widely recognized. The understanding of the molecular mechanisms involved in cancer and the development of nucleic acid delivery systems are two concepts that have led to this development. Systemic gene delivery systems are needed for therapeutic application to cells inaccessible by percutaneous injection and for multi-located tumor sites, i.e. metastases. Non-viral vectors based on the use of cationic lipids or polymers appear to have promising potential, given the problems of safety encountered with viral vectors. Using these non-viral vectors, the current challenge is to obtain a similarly effective transfection to viral ones. Based on the advantages and disadvantages of existing vectors and on the hurdles encountered with these carriers, the aim of this review is to describe the "perfect vector" for systemic gene therapy against cancer.