Simulated Biological Media Research Articles

Effects of sodium and potassium ions on a novel SeO2–B2O3–SiO2–P2O5–CaO bioactive system

The study is focused on Na2O and/or K2O influence on a new sol–gel derived SeO2–B2O3–SiO2–P2O5–CaO bioactive system.The structural changes induced by Na2O and/or K2O addition were correlated with the samples behavior in simulated biological media. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the structure and the type of the chemical bonds. The morphology of the samples was characterized through scanning electron microscopy (SEM). XRD results pointed out a prevalent vitreous structure with an incipient hydroxyapatite (HA) crystalline phase. FTIR results revealed a complex network consisting of silicate, phosphate and borate units, as well as the development of both A- and B-type of carbonate-substituted HA.The bioactivity of the samples was tested in vitro following the evolution of the apatite layers self-assembled on the samples surface in simulated body fluid. Their biocompatibility was investigated after samples surface functionalization with protein. The results indicate that sodium and potassium addition improves the biocompatibility by enhancement of protein adherence on samples surface and without to prevent the samples bioactivity.

Formulation and In Vitro Characterization of Thermosensitive Liposomes for the Delivery of Irinotecan

The effect of the lipid composition on the physicochemical properties of a liposomal carrier containing irinotecan (CPT-11) and its in vitro antitumoral activity on a colon cancer cell line has been investigated. The paper describes the procurement of a novel and easy-to-prepare temperature-sensitive carrier for CPT-11 and proves its suitability as delivery system on the basis of its ability to incorporate the drug and on its efficiency to promote drug internalization. Permeability data, studied in vitro in a simulated biological medium at different temperatures, showed that both the nature of the lipids and the ratio in which they have been mixed play a key role in the release of the encapsulated product. Stable temperature-sensitive liposomes with good drug incorporation efficiency were obtained and characterized. The cellular uptake and the cytotoxic activity of the CPT-11 liposomal formulation were compared with those corresponding to the free drug with promising results, being concentration and time dependent and significantly higher. Thus, it could be interpreted that the greatest cytotoxic effect of liposomal CPT-11 was because of the increased uptake provided by the liposomal carrier. Studies of cell cycle and annexin V binding showed drug-induced changes in cell cycle dynamics and the proapoptotic effect of liposomal CPT-11.

Release of Si from silicon, a ferrosilicon (FeSi) alloy and a synthetic silicate mineral in simulated biological media.

Unique quantitative bioaccessibility data has been generated, and the influence of surface/material and test media characteristics on the elemental release process were assessed for silicon containing materials in specific synthetic body fluids at certain time periods at a fixed loading. The metal release test protocol, elaborated by the KTH team, has previously been used for classification, ranking, and screening of different alloys and metals. Time resolved elemental release of Si, Fe and Al from particles, sized less than 50 µm, of two grades of metallurgical silicon (high purity silicon, SiHG, low purity silicon, SiLG), an alloy (ferrosilicon, FeSi) and a mineral (aluminium silicate, AlSi) has been investigated in synthetic body fluids of varying pH, composition and complexation capacity, simple models of for example dermal contact and digestion scenarios. Individual methods for analysis of released Si (as silicic acid, Si(OH)4) in synthetic body fluids using GF-AAS were developed for each fluid including optimisation of solution pH and graphite furnace parameters. The release of Si from the two metallurgical silicon grades was strongly dependent on both pH and media composition with the highest release in pH neutral media. No similar effect was observed for the FeSi alloy or the aluminium silicate mineral. Surface adsorption of phosphate and lactic acid were believed to hinder the release of Si whereas the presence of citric acid enhanced the release as a result of surface complexation. An increased presence of Al and Fe in the material (low purity metalloid, alloy or mineral) resulted in a reduced release of Si in pH neutral media. The release of Si was enhanced for all materials with Al at their outermost surface in acetic media.

Tetanus toxoids loaded glucomannosylated chitosan based nanohoming vaccine adjuvant with improved oral stability and immunostimulatory response.

The present report embarks on rational designing of stable and functionalized chitosan nanoparticles for oral mucosal immunization. Stable glucomannosylated sCh-GM-NPs were prepared by tandem cross linking method followed by lyophilization. The in vitro stability of antigen and formulation, cellular uptake and immunostimulatory response were assessed by suitable experimental protocol. Stability testing ensured the chemical and conformation permanency of encapsulated TT as well as robustness of sCh-GM-NPs in simulated biological media. The antigen release from sCh-GM-NPs followed initial burst followed by controlled Weibull's type of release profile. The higher intracellular uptake of sCh-GM-NPs in Raw 264.7 and Caco-2 was concentration and time dependent which mainly attributed to Clathrin and receptor mediated endocytosis via mannose and glucose receptor. The in vivo evaluation in animals revealed that sCh-GM-NPs posed significantly (p < 0.001) higher humoral, mucosal and cellular immune response than other counterparts. More importantly, commercial TT vaccine administered through oral or intramuscular route was unable to elicit all type of immune response. The sCh-GM-NPs could be considered as promising vaccine adjuvant for oral tetanus immunization. Additionally, this technology expected to benefit the design and development of stable peroral formulation for administration of protein, peptides and variety of other antigens.

Folate conjugated Mn3O4@SiO2 nanoparticles for targeted magnetic resonance imaging in vivo

The monodisperse silica-coated manganese oxide nanoparticles (Mn3O4@SiO2 NPs) were synthesized via the high temperature pyrolysis approach and were aminated through silanization. The amine-functionalized Mn3O4 NPs enabled the covalent conjugation of hydrophilic methoxypoly(ethylene glycol) (PEG) and the targeting ligand of folate (FA) onto their surface. The formed PEG and FA modified Mn3O4 NPs (Mn3O4@SiO2(PEG)–FA) exhibited the good colloidal stability in the simulated biological medium and the targeting ability to HeLa cells overexpressed the FA receptor. The T1-weighted magnetic resonance (MR) imaging and inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis of Mn3O4@SiO2(PEG)–FA NPs further demonstrated their targeting ability in tumor.

Development of Stabilized Glucomannosylated Chitosan Nanoparticles Using Tandem Crosslinking Method for Oral Vaccine Delivery

The aim of this study was to develop a novel platform technology, comprising of stable glucomannosylated chitosan nanoparticles, for oral immunization. Chitosan nanoparticles were stabilized by tandem crosslinking using tripolyphosphate followed by glutaraldehyde. Process and formulation variables were optimized using a 'Box-Behnken' design. The in vitro and in vivo performances were established in RAW 264.7 and BALB/c mice, respectively. The lyophilized formulation was exceptionally stable in simulated biological media and the enclosed antigen was conformationally stable. The mechanistic understanding of glucomannosylated chitosan nanoparticles in RAW 264.7 revealed transcellular uptake via both mannose and glucose transporter-mediated endocytosis. Glucomannan modification resulted in significantly higher systemic (serum IgG titer), mucosal (secretory IgA) and cell-mediated (IL-2 and IFN-γ) immune responses in comparison with nonmodified chitosan nanoparticles. The present strategy is expected to contribute some novel tools for the oral delivery of numerous biomacromolecules.

Size matters: Mechanism of metal release from 316L stainless steel particles is governed by size-dependent properties of the surface oxide

Size-dependent health aspects due to exposure to micro- or nano-sized particles can only be fully understood if their physicochemical properties are well characterized. The aim of this study was to explain the process of metal release from well-characterized inert gas atomized stainless steel 316L particles, sized<4µm (fine) and<45µm (coarse), in aggressive environments of relevance for inhalation and cellular uptake. This was accomplished by correlating new results from real-time metal release measurements with particle- and surface oxide characteristics. In simulated biological media with complexing properties, a complexation (ligand)-induced dissolution mechanism is dominating the metal release from fine 316L particles (having a homogeneous and amorphous Mn-rich surface oxide due to rapid cooling). At similar conditions, the coarse 316L particles show a metal release mechanism dominated by fast dissolution of surface oxide nanoparticles (rich in Mn, Fe, and some S), acting as initiation sites for metastable pitting corrosion.

Contributory roles of innate properties of cetyl alcohol/gelucire nanoparticles to antioxidant and anti-inflammation activities of quercetin.

The protective effects of synthetic lung surfactant Exosurf® (containing cetyl alcohol) against endotoxin-induced inflammation have been demonstrated in the literature. Thus, it is envisioned that nanoparticles loaded with quercetin (Q-NPs) prepared with binary mixtures of cetyl alcohol (CA) and Gelucire 44/14® (gelucire) as matrix materials will be capable of overcoming some of the protracted challenges confronting clinical application of quercetin and possess innate protective activity against inflammatory responses, which could be synergistic with quercetin. The NPs were stable in simulated biological media while retaining their particle size and spherical morphology. Further analysis by gel permeation chromatography, spectroscopic analysis (ultraviolet-visible, fluorescence, and Fourier transform infrared spectroscopy) indicated entrapment of quercetin in NPs. Q-NPs effectively enhanced xanthine oxidase inhibitory and free radical scavenging effect of quercetin. Furthermore, Q-NPs showed marked reduction (compared to quercetin alone) in production of nitric oxide and cytokine (interleukin-6 and tumor necrosis factor alpha) from lipopolysaccharide-activated macrophages. Superiority of Q-NPs over quercetin alone was confirmed from in vivo anti-inflammatory efficacy studies in BALB/c mice. Data from additional studies with blank NPs (without quercetin) showed that the NPs reported herein most likely possessed intrinsic protective properties against LPS-induced inflammation. Although further mechanistic studies are warranted, the overall work depicted a novel approach of possible exploiting innate protective properties of NPs in quercetin delivery for treating oxidative stress and inflammation.

SAR measurement due to mobile phone exposure in a simulated biological media

The specific absorption rate (SAR) measurements are carried out for compliance testing of personal 3G Mobile phone. The accuracy of this experimental setup has been checked by comparing the SAR in 10 gm of simulated tissue and an arbitrary shaped box. This has been carried out using a 3G mobile Phone at 1718.5 MHz, in a medium simulating brain and muscle phantom. The SAR measurement system consists of a stepper motor to move a monopole E-field probe in two dimensions inside an arbitrary shaped box. The phantom is filled with appropriate frequency-specific fluids with measured electrical properties (dielectric constant and conductivity). That is close to the average for gray and white matters of the brain at the frequencies of interest (1718.5 MHz). Induced fields are measured using a specially designed monopole probe in its close vicinity. The probe is immersed in the phantom material. The measured data for induced fields are used to compute SAR values at various locations with respect to the mobile phone location. It is concluded that these SAR values are position dependent and well below the safety criteria prescribed for human exposure.

Relationship between the size of nanoparticles and their adjuvant activity: Data from a study with an improved experimental design

There is a growing interest in identifying the relationship between the size of nanoparticles and their adjuvant activity, but the results from recent studies remain controversial. To address the controversy, it was thought that one should pay attention to the nanoparticle formulations to make sure that the antigen-loaded nanoparticles to be compared are not only different in particle size, but more importantly, as identical to each other as possible in all other formulation properties. In the present study, using ovalbumin (OVA) as a model antigen conjugated onto nanoparticles engineered from lecithin/glyceryl monostearate-in-water emulsions, we prepared OVA-nanoparticles of 230 nm and 708 nm. Before evaluating the immune responses induced by them in a mouse model, we made sure that: (i) the sizes of the two OVA-nanoparticles did not extensively overlap, (ii) the nanoparticles have similar zeta potentials and comparable antigen-loading, and (iii) the nanoparticles did not aggregate when suspended in simulated biological media. We then showed that when subcutaneously injected into mice, the 230 nm OVA-conjugated nanoparticles induced stronger OVA-specific antibody and cellular immune responses than the 708 nm OVA-nanoparticles. Future studies attempting to correlate the size of nanoparticles and their adjuvant activities need to consider formulation parameters to ensure that the particles are different only in size and are stable before and after injection.

Nanoparticles Based on PLGA:Poloxamer Blends for the Delivery of Proangiogenic Growth Factors

New blood vessel formation is a critical requirement for treating many vascular and ischemia related diseases, as well as for many tissue engineering applications. Angiogenesis and vasculogenesis, in fact, represent crucial processes for the functional regeneration of complex tissues through tissue engineering strategies. Several growth factors (GFs) and signaling molecules involved in blood vessels formation have been identified, but their application to the clinical setting is still strongly limited by their extremely short half-life in the body. To overcome these limitations, we have developed a new injectable controlled release device based on polymeric nanoparticles for the delivery of two natural proangiogenic GFs: platelet derived growth factor (PDGF-BB) and fibroblast growth factor (FGF-2). The nanoparticle system was prepared by a modified solvent diffusion technique, encapsulating the GF both in presence and in the absence of two stabilizing agents: bovine serum albumin (BSA) and heparin sodium salt (Hp). The developed nanocarriers were characterized for morphology, size, encapsulation efficiency, release kinetics in vitro and GF activity in cell cultures. The results have indicated that the coencapsulation of stabilizing agents can preserve the GF active structure and, in addition, increase their encapsulation efficiency into nanoparticles. Through this optimization process, we were able to raise the encapsulation efficiency of FGF-2 to 63%, and that of PDGF-BB to 87%. These PLGA:poloxamer blend nanoparticles loaded with GFs were able to release PDGF-BB and FGF-2 in a sustained fashion for more than a month. This work also confirms other positive features of PLGA:poloxamer nanoparticles. Namely, they are able to maintain their stability in simulated biological medium, and they are also nontoxic to cell culture models. Incubation of nanoparticles loaded with FGF-2 or PDGF-BB with endothelial cell culture models has confirmed that GFs are released in a bioactive form. Altogether, these results underline the interest of PLGA:poloxamer nanoparticles for the controlled delivery of GFs and substantiate their potential for the treatment of ischemic diseases and for tissue engineering applications.

Silver nanoparticles in simulated biological media: a study of aggregation, sedimentation, and dissolution

Nanoparticles, the building blocks of many engineered nanomaterials, can make their way into the environment or into organisms, either accidentally or purposefully. The intent of this study is to provide some insight into the complex environmental, health, and safety issues associated with engineered nanomaterials. In particular, here the state of commercially manufactured silver nanoparticles—i.e., will silver nanoparticles be present as isolated particles, agglomerates, or dissolved ions—in two simulated biological media is explored. Two different commercially manufactured silver nanoparticle samples, one that has been surface modified with a thick polymer coating to render them more water-soluble and the other, with a sub-nanometer surface layer, are studied. The experimental results and the extended DLVO model calculations show that silver nanoparticles have a propensity to settle out in high ionic strength media independent of surface modification. Furthermore, single nanoparticles as well as aggregates/agglomerates are present together in these solutions. Silver ion release in these simulated biological buffers with pHs of 4.5 and 7.4 is negligible after 96 h.

Fluoride-containing bioactive glasses: Surface reactivity in simulated body fluids solutions

The issue of the contribution of the addition of F to glass bioactivity is not well resolved. This work reports on the surface reactivity in different solutions (DMEM and Tris) for some potentially bioactive glasses based on the composition of 45S5 glass, in which CaF 2 is substituted alternately for (part of) CaO and Na 2O. The reactivity of F-containing glasses has been compared with that of the reference 45S5 system. The aim of this study is to explain in detail the mechanism of formation of an apatitic crystalline phase at the interface between the inorganic material and simulated biological media. A multi-technique investigation approach proposes a set of reactions involving Ca-carbonate formation, which are somewhat different from that formerly proposed by Hench for 45S5 bioactive glass, and which occur when a F-containing glass surface is in contact with a SBF. The usefulness of IR spectroscopy in recognizing the starting step of apatite (and/or FA) formation with respect to XRD technique is well established here.

Reactivity of Chromium(III) Nutritional Supplements in Biological Media: An X-Ray Absorption Spectroscopic Study

Chromium(III) nutritional supplements are widely used due to their purported ability to enhance glucose metabolism, despite growing evidence on low activity and the potential genotoxicity of these compounds. Reactivities of Cr(III) complexes used in nutritional formulations, including [Cr3O(OCOEt)6(OH2)3](+) (A), [Cr(pic)3] (pic=2-pyridinecarboxylato(-) (B), and trans-[CrCl2(OH2)4](+) (CrCl3.6H2O; C), in a range of natural and simulated biological media (artificial digestion systems, blood and its components, cell culture media, and intact L6 rat skeletal muscle cells) were studied by X-ray absorption near-edge structure (XANES) spectroscopy. The XANES spectroscopic data were processed by multiple linear-regression analyses with the use of a library of model Cr(III) compounds, and the results were corroborated by the results of X-ray absorption fine structure spectroscopy and electrospray mass spectrometry. Complexes A and B underwent extensive ligand-exchange reactions under conditions of combined gastric and intestinal digestion (in the presence of a semisynthetic meal, 3 h at 310 K), as well as in blood serum and in a cell culture medium (1-24 h at 310 K), with the formation of Cr(III) complexes with hydroxo and amino acid/protein ligands. Reactions of compounds A-C with cultured muscle cells led to similar ligand-exchange products, with at least part of Cr(III) bound to the surface of the cells. The reactions of B with serum greatly enhanced its propensity to be converted to Cr(VI) by biological oxidants (H2O2 or glucose oxidase system), which is proposed to be a major cause of both the insulin-enhancing activity and toxicity of Cr(III) compounds (Mulyani, I.; Levina, A.; Lay, P. A. Angew. Chem. Int. Ed. 2004, 43, 4504-4507). This finding enhances the current concern over the safety of consumption of large doses of Cr(III) supplements, particularly [Cr(pic)3].

INFLUENCE OF CaO/P2O5 RATIO ON THE CORROSION BEHAVIOR OF POTASSIUM-LIME-PHOSPHATE GLASSES IN SIMULATED BIOLOGICAL MEDIA

The dissolution of x CaO · (90-x) P 2 O 5 · 10 K 2 O glasses (x≤35 mol%) in simulated biological media (decationized water, physiological serum and chlorine acid, pH =1.5), at room temperature, in static regime during 24 h was investigated. The data indicates that the corrosion behavior of the samples depends on the pH of the solutions, glass composition and local structure. In the investigated time range, one observes two leaching stages relative to the incipient dissolution. In the first stage, the lowest release rate is obtained from the potassium-phosphate matrix in decationized water, while for the whole time the lowest leaching rate is recorded again in decationized water but from the sample containing small amount of lime, with CaO/P 2 O 5 ratio of 0.06. When the substitution of P 2 O 5 by CaO exceeds 50%, the release behavior changes in the investigated media.

Gadolinium incorporated reconstituted chylomicron emulsion for potential application in tumor neutron capture therapy

Gadolinium (Gd) neutron capture therapy (NCT) is currently under development as a potential approach for tumor therapy. Nanoparticles have been suggested as a potential delivery system to carry or target Gd to tumors for thermal or epithermal neutron irradiation. The reconstituted chylomicron emulsion is an artificial chylomicron remnant prepared using commercially available natural and biocompatible lipids. We proposed to use this nanometer-scale emulsion to deliver Gd to solid tumors by modifying the surface of the emulsion. A lipophilic Gd compound, gadolinium acetylacetonate (GdAcAc), was incorporated into the emulsion, resulting in a final pure Gd concentration of more than 1 mg/mL. The apparent solubility of GdAcAc was enhanced by about 6000-fold by this incorporation. The emulsion particles were shown to be stable in a two-week short-term stability study when stored at 4 °C. In addition, no extensive particle aggregation was observed when the emulsion particles were incubated in simulated biological media such as serum. Also, GdAcAc does not significantly ‘leak’ out from the emulsion particles. Only ∼5% was released in 20 h in a SDS (0.5% w/v) in phosphate buffered saline (pH 7.4, 10 mM) medium. Finally, the emulsion particles were coated with polyethylene glycol (PEG), and injected into Balb/C mice via the tail vein. A significant proportion (71.6±18.4%) of the PEG-coated, GdAcAc-incorporated emulsion remained circulating in the blood 5 h after the injection, while the PEG-free emulsion was mainly accumulated inside the liver. This chylomicron emulsion may be used to deliver Gd into solid tumors for NCT.

Influence of thermodynamic database on the modelisation of americium(III) speciation in a simulated biological medium

Summary An intercomparison exercise was led in order to study the impact of thermodynamic database (TDB) on the speciation of americium(III) in biochemical media. A first exercice was led, considering only the americium(III) species in solution. Even with different data sets, all the exercises are in relatively good agreement, concluding to successive complexation of the radioelement by phosphate (pH range from 0 to 3), citrate (pH range from 3 to 8) and hydroxo-carbonate (pH range from 8 to 14). Nevertheless, the speciation of americium differs for each pH range from one work to an other. These results are still observed when the speciation calculation includes the formation of solids. Nevertheless, some workers did not integrate in their data set the formation constant of Am(PO4). This solid is known to be very insoluble in typical biological media. All the calculations where Am(PO4) was not in the TDB presented a speciation where americium is solvated (mostly under citrate forms). When the formation of Am(PO4) is considered, the actinide is quantitatively present under this solid species. This work is a representative example of the impact of the thermodynamic data used in speciation exercises. Some exercices, using uncompleted TDB had wrong results and led to the conclusion of the necessity in the use of expertised and extended TDB.

Mechanical properties of calcia stabilized zirconia following in vivo and in vitro aging.

Aging studies were done on calcia stabilized zirconia rods of 72% theoretical density to determine the effect of actual and simulated biological environments on their strength. They were aged without stress in vitro in Ringer's solution for 1, 2 and 4weeks or in vivo in rabbits for 12 weeks. Rods aged in vitro showed mean losses in bending strength of 16, 17 and 19% respectively after 1, 2 and 4 weeks of immersion, while those aged in vivo showed a mean loss of 25%. It was concluded that the material tested would be unsatisfactory as an orthopedic replacement because of the rapid decrease in strength which occurred when exposed to actual or simulated biological media.