Surfactant-free Formulations Research Articles

Nanocomposite formulations of titanium dioxide and algal biomass: A rheological characterization for topical cosmetics and dermal applications

This study investigates rheological properties of novel, algae-based nanocomposites developed for potential use in dermal applications. The purpose of this investigation is to develop a highly tunable, biocompatible cosmetic base formulation and demonstrate how rheology relates to spreadability in its application. It was hypothesized that Spirulina biomass could be used in conjunction with titania (TiO2) nanoparticles and crosslinking and binding agents of calcium and/or citric acid to form nanocomposite materials with highly tunable rheological characteristics in absence of chemical surfactants. In this study, Arthrospira platensis (Spirulina) biomass, titanium (IV) dioxide, calcium chloride, and citric acid are used to develop a formulation that is then tested for a wide range of rheological characteristics and sensory-related properties. The rheological tests include amplitude sweep, frequency sweep, viscosity flow curve, 3-interval strain oscillatory thixotropy, and creep – recovery. Additionally, yield stress, complex viscosity, zero-shear viscosity, and power law indices were determined. The sensory-related properties that are discussed include formulation pH, static load spreadability, and dynamic shearing spreadability. After completing the investigation, it was concluded that the surfactant-free formulations were highly tunable, in terms of viscosity, rigidity, and thixotropy.

Combined Effect of Shaking Orbit and Vial Orientation on the Agitation-Induced Aggregation of Proteins

Orbital shaking in a glass vial is a commonly used forced degradation test to evaluate protein propensity for agitation-induced aggregation. Vial shaking in horizontal orientation has been widely recommended to maximize the air-liquid interface area while ensuring solution contact with the stopper. We evaluated the impact of shaking orbit diameter and frequency, and glass vial orientation (horizontal versus vertical) on the aggregation of three proteins prepared in surfactant-free formulation buffers. As soon as an orbit-specific frequency threshold was reached, an increase in turbidity was observed for the three proteins in vertical orientation only when using a 3 mm agitation orbit, and in horizontal orientation only when using a 30 mm agitation orbit. Orthogonal analyses confirmed turbidity was linked to protein aggregation. The most turbid samples had a visually more homogeneous appearance in vertical than in horizontal orientation, in line with the predicted dispersion of air and liquid phases obtained from computational fluid dynamics agitation simulations. Both shaking orbits were used to assess the performance of nonionic surfactants. We show that the propensity of a protein to aggregate in a vial agitated in horizontal or vertical orientation depends on the shaking orbit, and confirm that Brij® 58 and FM1000 prevent proteins from agitation-induced aggregation at lower concentrations than polysorbate 80.

Comparison of Protein Particle Formation in IgG1 mAbs Formulated with PS20 Vs. PS80 When Subjected to Interfacial Dilatational Stress.

Polysorbates (PS) are nonionic surfactants that are commonly included in protein formulations to mitigate the formation of interfacial stress-induced protein particles and thus increase their long-term storage stability. Nonetheless, factors that dictate the efficiency of different polysorbates in mitigating protein particle formation, especially during the application of interfacial stresses, are often ill defined. Here, we used a Langmuir trough to determine the surface activity of two IgG1 monoclonal antibodies formulated with two different polysorbates (PS20 and PS80) when subjected to interfacial dilatational stress. Interfacial properties of these formulations were then correlated with characterization of subvisible protein particles measured by micro-flow imaging (MFI). Both mAbs, when formulated in PS20, demonstrate faster adsorption kinetics and higher surface activity compared to PS80 or surfactant-free formulations. Compression/expansion results suggest that when exposed to interfacial dilatational stresses, both mAb/PS20 formulations display interfacial properties of PS20 alone. In contrast, interfacial properties of both mAb/PS80 formulations suggest mAbs and PS80 are co-adsorbed to the air-water interface. Further, MFI analysis of the interface and the bulk solution confirms that PS20 is more effective than PS80 at mitigating the formation of larger particles in the bulk solution in both mAbs. Concomitantly, the efficiency of PS to prevent interface-induced protein particle formation also depended on the protein's inherent tendency to aggregate at a surfactant-free interface. Together, the studies presented here highlight the importance of determining the interfacial properties of mAbs, surfactants, and their combinations to make informed formulation decisions about the choice of surfactant.

Cyclodextrin-based Pickering emulsions: functional properties and drug delivery applications.

Cyclodextrins (CDs) are biocompatible, cyclic oligosaccharides that are widely used in various industrial applications and have intriguing interfacial science properties. While CD molecules typically have low surface activity, they are capable of stabilizing emulsions by inclusion complexation of oil-phase components at the oil/water interface, which results in Pickering emulsion formation. Such surfactant-free formulations have gained considerable attention in recent years, owing to their enhanced physical stability, improved tolerability, and superior environmental compatibility compared to conventional, surfactant-based emulsions. In this review, we critically describe the latest insights into the molecular mechanisms involved in CD stabilization of Pickering emulsions, including covering practical aspects such as methods to prepare CD-based Pickering emulsions, lipid encapsulation, and relevant stability issues. In addition, the rheological and textural features of CD-based Pickering emulsions are discussed and particular attention is focused on promising examples for drug delivery, cosmetic, and nutraceutical applications. The functionality of currently developed CD-based Pickering emulsions is also summarised, including examples such as antifungal uses, and we close by discussing emerging possibilities to utilize the molecular encapsulation of CD-based emulsions for translational medicine applications in the antiviral and antibacterial spaces.

Bacterial Cellulose-Carboxymethyl Cellulose (BC:CMC) dry formulation as stabilizer and texturizing agent for surfactant-free cosmetic formulations

Generic cosmetic creams (oil-in-water emulsions) were prepared using dry Bacterial Cellulose and Carboxymethyl Cellulose (BC:CMC) to study the possibility of partially or completely replacing surfactants, while ensuring a long-term stability and the required organoleptic characteristics. BC:CMC was benchmarked against two hydrocolloidal Avicel products (PC-591 and PC-611), commonly used as thickeners and stabilizing aids in cosmetics production. The emulsions were then characterized regarding storage stability, rheology, texture and microscopic features.The full replacement of 5.5 % surfactants with only 0.75 % BC:CMC consistently showed similar results to those obtained with surfactants, namely concerning viscosity and texture. Although producing emulsions with larger oil droplets, BC:CMC provided for a very effective stabilization through a Pickering effect and by structuring the continuous phase. The more effective Avicel tested (PC-591) required a higher concentration (1.5 %) to achieve similar rheological profile but was ineffective in stabilizing the oil phase in a surfactant-free formulation with the adopted protocol. By replacing surfactants, dry BC:CMC matches a strong market need since both end users and manufacturers increasingly seek natural ingredients for cosmetic formulations.

Electrochemical tuning of reduced graphene oxide in printed electrolyte-gated transistors. Impact on charge transport properties

In this work, a surfactant-free formulation of inkjet-printable graphene oxide (GO) is described. The morphology of the printed layers on gold bottom-contact field-effect transistors is studied using atomic force and optical microscopies. An in-situ approach of “green” electrochemical reduction of non-conducting GO into its conductive reduced form, i.e. rGO, is developed. A very significant effect of the reduction degree is observed on the electrical characterizations of rGO in the electrolyte-gated transistor configuration (EGFET), notably on its Dirac point (charge neutrality point) which can be shifted on a range of 1 V. This tuning of the doping level of rGO as a function of the reduction time goes hand in hand with the modulation of charge carriers' mobility over more than one order of magnitude.

Simplified Fabrication for Ion-Selective Optical Emulsion Sensor with Hydrophobic Solvatochromic Dye Transducer: A Cautionary Tale.

It has recently been reported that polystyrene microbeads may be modified to realize plasticizer-free ion-selective optical sensors (optodes) on the basis of solvatochromic dye transducers. We show here that the functionalized microbeads, individually isolated by flow cytometry, exhibit unexpectedly poor fluorescent properties and that the sensor response is instead attributed to the supernatant. A more thorough study reveals that such optical microemulsion sensors can be made operationally functional and chemically selective, seemingly in the absence of any solvent matrix or added surfactant. Instead, it is shown that residual THF used in the fabrication of the emulsified sensors may solubilize the sensing components and give a functional optode response. To evaluate this further, the number of sensing components was stepwise simplified to assess their need. Variation of residual THF levels has no effect on the ion optode response when plasticizer is present, in support of established results. Lipophilic solvatochromic dye transducers are also shown not to require an added surfactant as their nature already endows the emulsified sensors with a stabilizing ionic surface charge. The ionophores are shown to exhibit much larger stability constants in the surfactant-free formulations than surfactant-based ones (valionomycin, log β > 9.2 compared to 6.1; Na+-ionophore X, 6.7 vs 4.7), which is attributed to a less polar solvent environment for the ionophore. Potassium-, sodium-, and calcium-selective sensors were used as model systems in this study.

Interfacial Activity of Nonamphiphilic Particles in Fluid-Fluid Interfaces.

Surfactants can adsorb in fluid-fluid interfaces and lower the interfacial tension. Like surfactants, particles with appropriate wettability can also adsorb in fluid-fluid interfaces. Despite many studies of particle adsorption at fluid interfaces, some confusion persists regarding the ability of (simple, nonamphiphilic) particles to reduce the interfacial tension. In the present work, the interfacial activity of silica nanoparticles at air-water and hexadecane-water interfaces and of ethyl cellulose particles at the interface of water with trimethylolpropane trimethacrylate was analyzed through pendant drop tensiometry. Our measurements strongly suggest that the particles do significantly affect the interfacial tension provided that they have a strong affinity to the interface by virtue of their wettability and that no energy barrier to adsorption prevents them from reaching the interface. A simplistic model that does not explicitly account for any particle-particle interactions is found to yield surprisingly good predictions for the effective interfacial tension in the presence of the adsorbed particles. We further propose that interfacial tension measurements, when combined with information about the particles' wetting properties, can provide a convenient way to estimate the packing density of particles in fluid-fluid interfaces. These results may help to understand and control the assembly of nonamphiphilic nanoparticles at fluid-fluid interfaces, which is relevant to applications ranging from surfactant-free formulations and food technology to oil recovery.

Surfactant Effects on Particle Generation in Antibody Formulations in Pre-filled Syringes

Protein aggregation and particle formation have been observed when protein solutions contact hydrophobic interfaces, and it has been suggested that this undesirable phenomenon may be initiated by interfacial adsorption and subsequent gelation of the protein. The addition of surfactants, such as polysorbate 20, to protein formulations has been proposed as a way to reduce protein adsorption at silicone oil-water interfaces and mitigate the production of aggregates and particles. In an accelerated stability study, monoclonal antibody formulations containing varying concentrations of polysorbate 20 were incubated and agitated in pre-filled glass syringes (PFS), exposing the protein to silicone oil-water interfaces at the siliconized syringe walls, air-water interfaces, and agitation stress. Following agitation in siliconized syringes that contained an air bubble, lower particle concentrations were measured in the surfactant-containing antibody formulations than in surfactant-free formulations. Polysorbate 20 reduced particle formation when added at concentrations above or below the critical micelle concentration (CMC). The ability of polysorbate 20 to decrease particle generation in PFS corresponded with its ability to inhibit gelation of the adsorbed protein layer, which was assessed by measuring the interfacial diffusion of individual antibody molecules at the silicone oil-water interface using total internal reflectance fluorescence (TIRF) microscopy with single-molecule tracking.

Protein Aggregation and Particle Formation in Prefilled Glass Syringes

The stability of therapeutic proteins formulated in prefilled syringes (PFS) may be negatively impacted by the exposure of protein molecules to silicone oil-water interfaces and air-water interfaces. In addition, agitation, such as that experienced during transportation, may increase the detrimental effects (i.e., protein aggregation and particle formation) of protein interactions with interfaces. In this study, surfactant-free formulations containing either a monoclonal antibody or lysozyme were incubated in PFS, where they were exposed to silicone oil-water interfaces (siliconized syringe walls), air-water interfaces (air bubbles), and agitation stress (occurring during end-over-end rotation). Using flow microscopy, particles (≥2 μm diameter) were detected under all conditions. The highest particle concentrations were found in agitated, siliconized syringes containing an air bubble. The particles formed in this condition consisted of silicone oil droplets and aggregated protein, as well as agglomerates of protein aggregates and silicone oil. We propose an interfacial mechanism of particle generation in PFS in which capillary forces at the three-phase (silicone oil-water-air) contact line remove silicone oil and gelled protein aggregates from the interface and transport them into the bulk. This mechanism explains the synergistic effects of silicone oil-water interfaces, air-water interfaces, and agitation in the generation of particles in protein formulations.

Characterization of an antioxidant surfactant-free topical formulation containing Castanea sativa leaf extract

Context: Inclusion of antioxidants in topical formulations can contribute to minimize oxidative stress in the skin, which has been associated with photoaging, several dermatosis and cancer.Objective: A Castanea sativa leaf extract with established antioxidant activity was incorporated into a semisolid surfactant-free formulation. The objective of this study was to perform a comprehensive characterization of this formulation.Materials and methods: Physical, microbiological and functional stability were evaluated during 6 months storage at 20 °C and 40 °C. Microstructure elucidation (cryo-SEM), in vitro release and in vivo moisturizing effect (Corneometer® CM 825) were also assessed.Results and discussion: Minor changes were observed in the textural and rheological properties of the formulation when stored at 20 °C for 6 months and the antioxidant activity of the plant extract remained constant throughout the storage period. Microbiological quality was confirmed at the end of the study. Under accelerated conditions, higher modifications of the evaluated parameters were observed. Cryo-SEM analysis revealed the presence of oil droplets dispersed into a gelified external phase. The release rate of the antioxidant compounds (610 ± 70 µgh−0.5) followed Higuchi model. A significant in vivo moisturizing effect was demonstrated, that lasted at least 4 h after product’s application.Conclusion: The physical, functional and microbiological stability of the antioxidant formulation was established. Specific storage conditions should be recommended considering the influence of temperature on the stability. A skin hydration effect and good skin tolerance were also found which suggests that this preparation can be useful in the prevention or treatment of oxidative stress-mediated dysfunctions.

Enhanced recovery and dissolution of griseofulvin nanoparticles from surfactant-free nanocomposite microparticles incorporating wet-milled swellable dispersants

Nanocomposite microparticles (NCMPs) incorporating drug nanoparticles and wet-milled swellable dispersant particles were investigated as a surfactant-free drug delivery vehicle with the goal of enhancing the nanoparticle recovery and dissolution rate of poorly water-soluble drugs. Superdisintegrants were used as inexpensive, model, swellable dispersant particles by incorporating them into NCMP structure with or without wet-stirred media milling along with the drug. Suspensions of griseofulvin (GF, model drug) along with various dispersants produced by wet-milling were coated onto Pharmatose® to prepare NCMPs in a fluidized bed process. Hydroxypropyl cellulose (HPC, polymer) alone and with sodium dodecyl sulfate (SDS, surfactant) was used as base-line stabilizer/dispersant during milling. Croscarmellose sodium (CCS, superdisintegrant) and Mannitol were used as additional dispersants to prepare surfactant-free NCMPs. Nanoparticle recovery during redispersion and dissolution of the various GF-laden NCMPs were examined. Suspensions prepared by co-milling GF/HPC/CCS or milling GF/HPC/SDS were stable after 30 h of storage. After drying, due to its extensive swelling capacity, incorporation of wet-milled CCS in the NCMPs caused effective breakage of the NCMP structure and bursting of nanoparticle clusters, ultimately leading to fast recovery of the GF nanoparticles. Optimized wet co-milling and incorporation of CCS in NCMP structure led to superior dispersant performance over incorporation of unmilled CCS or physically mixed unmilled CCS with NCMPs. The enhanced redispersion correlated well with the fast GF dissolution from the NCMPs containing either CCS particles or SDS. Overall, swellable dispersant (CCS) particles, preferably in multimodal size distribution, enable a surfactant-free formulation for fast recovery/dissolution of the GF nanoparticles.

Abstract 581: Surfactant-free PLGA encapsulation facilitates delivery of LY294002 to endoplasmic reticulum and enhances its cytotoxicity.

Abstract LY294002 (LY) is a potent inhibitor of phosphatidylinositol 3-kinases (PI3Ks); however, bio-applications of LY are limited by its poor solubility and pharmacokinetic profile. Poly(lactic-co-glycolic acid) (PLGA) is a biodegradable nanomaterial that can be used as a carrier for drug delivery. Although LY-loaded polyvinyl alcohol (PVA)-containing PLGA nanoparticles (PVA-LY NPs) have been developed to improve LY solubility, the ratio of NP internalization is unsatisfactory and the cytotoxicity of PVA-LY NPs is inferior to that of free LY. LY-loaded surfactant-free PLGA nanoparticles (SF-LY NPs) were developed to improve the therapeutic efficacy of LY. The size of SF-LY NPs was in the range of 80-100 nm, the shape was spherical and the NPs were monodispersed. The loading capacity of LY in SF NPs was 7.4μg/mg with a sustained-released pattern. In four lung cancer cell lines, SF-LY NPs showed a stronger growth inhibitory effect, sustained suppression of the serine/threonine kinase AKT activation, and increased intracellular uptake of LY compared with PVA-LY NPs or free LY. In addition, it was observed that SF NPs tend to accumulate in the endoplasmic reticulum (ER) and subsequently induce pronounced ER stress. After injection into tumors, SF-LY NPs exhibited a stronger antitumor effect than free LY. These findings indicated that the surfactant-free formulation of PLGA is an ideal vector to carry LY and that SF-LY NPs possess promising anticancer activity. Citation Format: Chia-Cheng Hou. Surfactant-free PLGA encapsulation facilitates delivery of LY294002 to endoplasmic reticulum and enhances its cytotoxicity. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 581. doi:10.1158/1538-7445.AM2013-581

Pronounced induction of endoplasmic reticulum stress and tumor suppression by surfactant-free poly (lactic-co-glycolic acid) nanoparticles via modulation of the PI3K signaling pathway

BackgroundY294002 (LY) is a potent inhibitor of phosphatidylinositol 3-kinases (PI3Ks); however, biological applications of LY are limited by its poor solubility and pharmacokinetic profile. This study aimed at developing LY-loaded surfactant-free poly(lactic-co-glycolic acid) (PLGA) nanoparticles (SF-LY NPs) to improve the therapeutic efficacy of LY.Materials and methodsCellular viability was measured by MTT assay. The subcellular distribution of NPs was studied using an ultraviolet-visible spectrophotometer and confocal microscope. The expression of cell-death-associated proteins was determined using Western blotting and the in vivo activity of SF-LY NPs was tested in a xenograft animal model.ResultsSF-LY NPs enhanced the intracellular level of LY, induced sustained suppression of AKT, and induced marked cancer cell death. In addition, SF-LY NPs tended to accumulate in the endoplasmic reticulum (ER) and induce pronounced ER stress. Finally, SF-LY NPs exhibited a prominent antitumor effect in vivo.ConclusionThe surfactant-free formulation of PLGA is critical to the promising anticancer activity of SF-LY NPs.

Oral bioavailability of ketoprofen in suspension and solution formulations in rats: the influence of poloxamer 188

The aim of the current study was to investigate the effect of poloxamer 188 (P-188) on the bioavailability of the BCS class 2 drug ketoprofen in vivo. Aqueous suspension and solution formulations of ketoprofen with and without P-188 were orally administered to fasted male Wistar rats. The intrinsic dissolution rate and solubility of ketoprofen in simulated intestinal fluid, in both the presence and absence of P-188, was measured. The AUC and C(max) were found to be significantly enhanced when ketoprofen was administered as suspension and P-188 was present in the formulation (Susp P-188) as compared to the surfactant-free formulation (∼4-fold higher AUC, 7-fold higher C(max) ). While drug solubility appeared to be almost unaffected by P-188, a significantly faster dissolution was observed. In addition, the influence of P-188 on the drug absorption process was investigated by comparison of solution formulations with and without P-188. The in-vivo performance of these solutions, a pure buffer solution and a P-188-containing buffer solution showed no significant difference, suggesting that the increase in bioavailability for Susp P-188 was primarily a consequence of the dissolution rate-enhancing effect.

Surfactant-free Formulation of Poly(Lactic/Glycolic) Acid Nanoparticles Encapsulating Functional Polypeptide: A Technical Note

Therapeutic proteins or polypeptides can be formulated into various particulate delivery systems including the polymeric carriers to avoid rapid degradation and to maintain the sustained release for better therapeutic effects (1). Poly(lactic/glycolic) acid (PLGA) micro/nanoparticle is a widely used formulation agent because of its good biodegradability, biocompatibility, and approved clinical usage, which have been available in the market to treat prostate cancer, acromegaly, periodontal disease, and pediatric growth hormone deficiency (2). The sustaining and complete release of proteins in their native or active forms from the PLGA micro/nanoparticles is often a challenging task (3). Proteins are generally formulated into PLGA nanoparticles by water/oil/water double-emulsion–solvent evaporation method, which generates hydrophilic/hydrophobic interface that may result in the unfolding or denaturing of protein molecules (4). Thus, polymeric surfactants are usually used to lower surface tension of protein solutions and to prevent aggregation of protein molecules at hydrophobic surface (1). Polyvinyl alcohol (PVA) is a widely used polymeric surfactant in the exterior aqueous phase as an emulsifier. However, the safety of PVA still appears to be a concern from the previous literature reports (5,6). Following repeated subcutaneous or intravenous administrations of PVA, various organ lesions and hypertension have been reported in rats, and central nervous system depression and anemia followed by renal damage have also been reported in beagle dogs; whereas, orally administered PVA is relatively harmless in mice or rat (5,6). Therefore, residual PVA was always removed by washing procedures such as repetitive centrifugation (7) or filtration (8), which removes not only the PVA but also the unencapsulated proteins or polypeptides, which might be often valuable or hard to collect. Hence, a few substituting emulsifiers have been studied. For example, poly(ethylene glycol) (PEG) was used successfully as the stabilizer to prepare enzyme-loaded PLGA microparticles (9). Besides, surfactant-free formulation was achieved by nanoprecipitation/solvent-displacement method that would not alter surface properties of PLGA nanoparticles, but this method may suffer the low encapsulation efficiency when low protein concentration solution is to be used (10). In the present study, we introduced another surfactant-free method to prepare PLGA nanoparticles encapsulating polypeptides by double-emulsion–solvent evaporation method. We used sucrose as the stabilizer of the exterior aqueous phase to prevent aggregation of PLGA nanoparticles during formulation process. Nerve growth factor (NGF), a small secreted protein which can induce the differentiation and survival of particular target neurons, was used as the model protein. As sucrose is a nontoxic material, additional washing procedures are not necessarily needed for NGF-loaded PLGA nanoparticles, and thus, the valuable NGF loss can be minimized. The release of functional NGF molecules from these nanoparticles was verified by either the antibody recognition in enzyme-linked immunosorbent assay (ELISA) method or the induction on the neurite outgrowth of PC-12 cells.

Induction and analysis of aggregates in a liquid IgG1-antibody formulation

The objective of this study was to compare different agitation stress methods (stirring in Reacti Vials TM versus horizontal shaking) in their effect on protein destabilization, to assess several analytical techniques (light obscuration, turbidimetric and light scattering analysis) for detection of aggregates of various sizes and to evaluate the protecting effect of polysorbate 80 on protein aggregation. A monoclonal IgG1 antibody was used as model protein. Both mechanical stress methods can provoke aggregate formation. The method of stirring induces particles in the range of 10–25 μm comparable to shaking stress. However, stirred samples show a much higher absorbance and reveal a second particle species in DLS analysis, suggesting that stirring stress induces a higher amount of smaller protein aggregates. Addition of polysorbate 80 protects the antibody against aggregation. Only in stirred samples a slight increase in sub-visible particles and turbidity was noted. However, a greater extent of aggregation products was detected by DLS as compared to surfactant-free formulations. Thus, polysorbate 80 appears to stabilise small aggregates and prevents further proceeding of the aggregation process. The induction of aggregates by stirring stress in Reacti Vials TM analysed by absorbance measurement seems to be a good combination for high-throughput formulation studies.