Self-assembly Of Nonionic Surfactants Research Articles

A Detailed Review on Fast Dissolving Niosomal Films for Sublingual Drug Delivery

Fast dissolving or Quick-dissolving dosage forms have great importance in the pharmaceutical field due to their special properties and advantages. Fast-dissolving dosage forms breakdown immediately in the salivary fluids of the oral cavity within a minute, where they release the active pharmaceutical ingredient. Sublingual drug delivery system is a novel route of drug administration in which the drug substance is placed under the tongue and is directly absorbed via the blood vessels and produces the immediate onset of action. Noisome are closed bilayer vesicles formed by self-assembly of nonionic surfactant in an aqueous medium. Noisome is similar to liposome but has the ability to increase the stability of the drug. Formulated niosomes are added into the film-forming polymers to obtain sublingual niosomal films. Fast dissolving niosomal film is suitable for the drugs which show high first-pass metabolism or hepatic metabolism, low bioavailability drugs, and have a short half-life drugs. Fast Dissolving Niosomal Films used to improve the oral bioavailability and reduce the dose and dosing frequency, which reduce systemic side effects and as well as cost-effective. Niosomes allow the prolonged release of the drug and film was used to increase the bioavailability of drugs via the sublingual route of drug administration. Fast dissolving niosomal films have great importance during emergency conditions like allergy, short-term spasm, and asthma whenever an immediate onset of action is required. Fast dissolving films are also suitable for pediatric, geriatric, and dysphasic patients or patients with fear of choking.

Gigantic Magnetic Field Effect on the Long-Lived Intermolecular Charge-Separated State Created at the Nonionic Bilayer Membrane

For realization of low-cost organic photon-energy conversion, the supramolecular approach has been a focus of attention as a counter approach to precise synthesis of covalently linked donor (D)-acceptor (A) molecules. Here we report photogeneration of a long-lived (∼3 μs) intermolecular charge-separated (CS) state of metal porphyrins (D) and an alkyl viologen (A) at an interface of a vesicle membrane formed by self-assembly of nonionic surfactant and cholesterol molecules. The yield of escaped free radicals is negligibly low as in the case of CS states in covalently linked D-A systems. Furthermore, the transient concentration of the CS state dramatically increases by ∼100% upon application of a magnetic field of 250 mT at room temperature. The simulation of the spin dynamics of the CS state indicates that fast (∼107 s-1) spin-selective recombination and slow (105-106 s-1) dissociation-re-encounter dynamics are the key processes for the long CS-state lifetime and the gigantic magnetic field effect. It has turned out that such dynamics are sharply dependent on temperature and alkyl chain length of the viologen. The present results would lead to the development of future materials for light energy conversion, drug delivery, and microscopic bioprobes.

Self-assembly and Rheological Properties of C12EO4and Aminosilane Mixtures

Phase behavior, self-assembly, and rheological properties of 3-aminopropyltriethoxysilane (APTES) and nonionic surfactant, CH3(CH2)11(OCH2CH2)4OH (C12EO4), in water were studied. The self-assembled structures were determined by means of small angle X-ray scattering (SAXS), cryo-transmission electron microscopy (cryo-TEM), freeze-fracture TEM (FF-TEM), and 2 H nuclear magnetic resonance ( 2 H NMR) measurements and the properties of self-assembled mixtures were obtained by rheological measurements. With a variation of the composition, different self-assembled structures were ob- tained. In the Lα phase region, a phase structural transition from an aggregate with high curvatures to the lamellar structures with low curvatures is observed with an increase of APTES concentration at a constant concentration of C12EO4. At constant APTES concentration, with an increase of C12EO4 concentration, densely packed vesicles and planarly lamellar structures which behave the properties as gel-like solutions having the rather high viscosity coexist. The phase structural transition was considered to be induced by the insertion of the hydrolytic products of APTES into the palisade of the micelles of C12EO4. These new observations on phase structural transition and self-assembly of nonionic surfactant and aminosilane mixtures could be very important for the full understanding for their applications, especially as templates in the synthesis of silica ma- terials, etc. Keywords phase behavior; nonionic surfactant; aminosilane; rheological property; cryo-TEM

Structural Characterization of Surfactant Aggregates Adsorbed in Cylindrical Silica Nanopores

The self-assembly of nonionic surfactants in the cylindrical pores of SBA-15 silica with a pore diameter of 8 nm was studied by small-angle neutron scattering (SANS) at different solvent contrasts. The alkyl ethoxylate surfactants C(10)E(5) and C(12)E(5) exhibit strong aggregative adsorption in the pores as indicated by the sigmoidal shape of the adsorption isotherms. The SANS intensity profiles can be represented by a sum of two terms, one accounting for diffuse scattering from surfactant aggregates in the pores and the other for Bragg scattering from the pore lattice of the silica matrix. The Bragg reflections are analyzed with a form factor model in which the radial density profile of the surfactant in the pore is approximated by a two-step function. Diffuse scattering is represented by a Teubner-Strey-type scattering function which indicates a preferred distance between adsorbed surface aggregates in the pores. Our results suggest that adsorption starts with formation of discrete surface aggregates which increase in number and eventually merge to interconnected patches as the plateau value of the adsorption isotherm is approached. A grossly different behavior, viz. formation of micelles as in solution, is found for the maltoside surfactant C(10)G(2), in agreement with the observed weak adsorption of this surfactant in SBA-15.

Controlled Self-Assembly of Monodisperse Niosomes by Microfluidic Hydrodynamic Focusing

Niosomes are synthetic membrane vesicles formed by self-assembly of nonionic surfactant, often in a mixture with cholesterol and dicetyl phosphate. Because of their inner aqueous core and bilayer membrane shell, niosomes are commonly used as carriers of treatment agents for pharmaceutical and cosmetic applications or contrast agents for clinical imaging applications. In those applications, niosomes are considered as a more economical and stable alternative to their biological counterpart (i.e., liposomes). However, conventional bulk method of niosome preparation requires bulk mixing of two liquid phases, which is time-consuming and not well-controlled. Such mixing conditions often lead to large niosomes with high polydispersity in size and thus affect the consistency of niosome dosage or imaging quality. In this study, we present a new method of niosome self-assembly by microfluidic hydrodynamic focusing to improve on the size and size distributions of niosomes. By taking advantage of the rapid and controlled mixing of two miscible fluids (i.e., alcohol and water) in microchannels, we were able to obtain in seconds nanoscaled niosomes with approximately 40% narrower size distributions compared to the bulk method. We further investigated different parameters that might affect on-chip assembly of niosomes, such as (1) conditions for the microfluidic mixing, (2) chemical structures of the surfactant used (i.e., sorbitan esters Span 20, Span 60, and Span 80), and (3) device materials for the microchannel fabrication. This work suggests that microfluidics may facilitate the development and optimization of biomimetic colloidal systems for nanomedicine applications.

Self-Assembly of Nonionic Surfactants into Lyotropic Liquid Crystals in Ethylammonium Nitrate, a Room-Temperature Ionic Liquid

The stability of a variety of lyotropic liquid crystals formed by a number of polyoxyethylene nonionic surfactants in the room-temperature ionic liquid ethylammonium nitrate (EAN) is surveyed and reported. The pattern of self-assembly behaviour and mesophase formation is strikingly similar to that observed in water, even including the existence of a lower consolute boundary or cloud point. The only quantitative difference from water is that longer alkyl chains are necessary to drive the formation of liquid crystalline mesophases in EAN, suggesting that a rich pattern of "solvophobic" self-assembly should exist in this solvent.

The effect of processing variables on the physical characteristics of non-ionic surfactant vesicles (niosomes) formed from a hexadecyl diglycerol ether

Niosomes are vesicles formed by self-assembly of non-ionic surfactants. In this investigation, the effects of processing variables, particularly temperature and sonication, on the physical characteristics and phase transitional behaviour of two niosomal systems based on a hexadecyl diglycerol ether (C 16G 2) have been studied. Systems containing C 16G 2, cholesterol and poly-24-oxyethylene cholesteryl ether (Solulan C24) in the molar ratios 91:0:9 and 49:49:2 were prepared by aqueous dispersion of films, followed by examination of 5(6)-carboxyfluorescein entrapment, particle size and morphology. The thermal behaviour was examined using high sensitivity differential scanning calorimetry (HSDSC) and hot stage microscopy, while the effects of sonication were studied in terms of size and morphology, both immediately after preparation and on storing for 1 h at room temperature and 60°C. Polyhedral niosomes were formed from systems containing C 16G 2 and Solulan C24 alone, while cholesterol-containing systems formed spherical vesicles mixed with tubular structures; the polyhedral systems were found to have a larger particle size and higher CF entrapment efficiency. HSDSC studies showed the polyhedral systems to exhibit an endotherm at 45.4°C and a corresponding exotherm at 39.1°C on cooling which were ascribed to a membrane phase transition; no equivalent transition was observed for the cholesterol containing systems. Hot stage microscopy showed the polyhedral vesicles to convert to spherical structures at ∼48°C, while on cooling the spherical vesicles split into smaller structures and reverted to the polyhedral shape at ∼49°C. Sonication resulted in the polyhedral vesicles forming spherical structures which underwent a particle size increase on storage at room temperature but not at 60°C. The study suggests that the polyhedral vesicles undergo a reversible transition to spherical vesicles on heating or sonication and that this morphological change may be associated with a membrane phase transition.

Non-ionic surfactant based vesicles (niosomes) in drug delivery

The self assembly of non-ionic surfactants into vesicles was first reported in the seventies by researchers in the cosmetic industry. Since then a number of groups world wide have studied non-ionic surfactant vesicles (niosomes) with a view to evaluating their potential as drug carriers. This article presents a summary of the achievements in the field to date. Niosomes may be formed form a diverse array of amphiphiles bearing sugar, polyoxyethylene, polyglycerol, crown ether and amino acid hydrophilic head groups and these amphiphiles typically possess one to two hydrophobic alkyl, perfluoroalkyl or steroidal groups. The self assembly of surfactants into niosomes is governed not only by the nature of the surfactant but by the presence of membrane additives, the nature of the drug encapsulated and the actual method of preparation. Methods of niosome preparation and the number of different morphologies that have been identified are detailed. The influence of formulation factors on niosome stability is also examined as are methods to optimise drug loading. In vivo these systems have been evaluated as immunological adjuvants, anti-cancer/anti-infective drug targeting agents and carriers of anti-inflammatory drugs. Niosomes have also been used in diagnostic imaging. Efforts to achieve transdermal and ophthalmic drug delivery with some formulations are also discussed.