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The biotin-based low molecular weight hydrogel (G1) is able to entrap the epMB and as a consequence, the color of the epMB changes from green to blue; the color change depends on the state of the gelator, i.e. upon proceeding from sol to gel and vice versa.

Novel covalent gels were prepared by complexation of polymer-bound catechols with NaBH4 at pH ≈ 9. These gels can absorb humidity, which changes the catechol–borate covalent bonds from irreversible to reversible. Furthermore, humidity induces self-healing, proven by rheological data.

For improving the therapeutic efficiency of tumors and decreasing undesirable side effects, ternary complexes were developed by coating pH-sensitive PEG-b-PLL-g-succinylsulfathiazole (hereafter abbreviated as PPSD) with DNA/PEI polyplexes via electrostatic interaction. PPSD can efficiently shield the surface charge of DNA/PEI. The gene transfection efficiency of ternary complexes was lower than that of DNA/PEI at pH 7.4; however, it recovered to the same level as that of DNA/PEI at pH 6.0, attributed to the pH-triggered release of DNA/PEI from ternary complexes. Cell uptake results also exhibited the same trend as transfection at different pH values. The suitable ability for pH-triggered shielding/deshielding estimated that PPSD demonstrates potential as a shielding system for use in in vivo gene delivery.

The objective of the present research was to develop a novel pH triggered nanoemulsified in-situ gel (NE-ISG) for ophthalmic delivery of fluconazole (FLZ) to enhance the permeation and residence time of the formulation, by overcoming the limitations associated with protective ocular barriers. Pseudoternary phase diagrams were constructed using capmul MCM (oil phase), tween 80 (surfactant) and transcutol P (cosurfactant) to identify the NE region. Nanoemulsions (NE1-NE6) of FLZ were prepared by spontaneous emulsification method and evaluated for various pharmacotechnical characteristics. NE4 was selected as optimized NE and was dispersed in carbopol 934 solution to form nanoemulsified sols (NE-ISG1 to NE-ISG5) that were expected to convert in to in-situ gels at corneal pH (7.4). The optimized NE-ISG was selected on the basis of gelation ability with a residence time up to or more than 6 h. Ex-vivo transcorneal permeation study displayed significantly higher (p < 0.05) permeation of FLZ from NE-ISG5 (337.67 µg/cm(2)) and NE4 (419.30 µg/cm(2)) than the commercial eye drops (112.92 µg/cm(2)). Hen's egg test-Chorioallantoic membrane (HET-CAM) test with zero score indicated the non-irritant property of developed NE-ISG5. Corneal toxicity study revealed no visual signs of tissue damage. Hence it can be concluded that NE-ISG5 may offer a more intensive treatment of ocular fungal infections due to higher permeation, prolonged precorneal residence time and sustained drug release along with higher in-vitro efficacy, safety and greater patient compliance.

With the decrease in pH value, the ‘nano-flower’ exhibited a half-open state to expose the target ligands on the surface under tumor acidic conditions and fully bloomed to release Dox under endosomal acidic conditions.

Amphoteric calix[8]arene with negatively charged upper rim and positively charged lower rim was synthesized based on water-soluble p-sulfonato-calix[8]arene. The pH-sensitive amphoteric calix[8]arenes exhibit not only a good hydrophobic drug loading capacity but also a pH-triggered drug releasing behavior. The in vitro release studies demonstrated that release of ciprofloxacin from amphoteric calix[8]arene complexes was highly pH-sensitive. More efficient drug release was observed at mildly acidic pH 5.0 and basic pH 8.5 compared to physiological pH. The amphoteric calix[8]arene complexes hold out great promise of being pH-sensitive drug carrier.

This paper describes how LTE Rel' 8 power headroom report (PHR) can be used to detect outage problems in LTE networks. The paper outlines the proposed minimization of drive tests use case for PH triggered measurements, alleviates the problems in this proposal, and describes improvements which can help operators to gather more coverage and outage related information from their networks. The article points out, that the earlier proposal can lead to unnecessary signaling, it does not work always as supposed, and the existing measurements can be used to gather the same information. The study is conducted by simulating two different outage problem scenarios with a fully dynamic LTE system simulator.

E.-K. Lim , Prof. S. Haam Department of Chemical and Biomolecular EngineeringYonsei UniversitySeoul 120-749, Republic of Korea E-mail: haam@yonsei.ac.kr Prof. .-M. Y Huh , Prof. J. ang , Y Prof. J.-S. Suh Department of RadiologyYonsei UniversitySeoul 120-752, Republic of KoreaE-mail: jss@yuhs.ac Prof. .-M. Y Huh , Prof. J. ang , Y Prof. J.-S. Suh , Prof. S. Haam YUHS-KRIBB Medical Convergence Research InstituteSeoul 120-752, Republic of Korea Prof. .-M. Y Huh , Prof. J.-S. Suh Severance Biomedical Science Institute(SBSI)Seoul 120-752, Republic of Korea Prof. K. Lee Department of ChemistryKorea UniversitySeoul 136-701, Republic of Korea

The O-acyl isopeptide method has recently gained attention as an efficient protocol for the synthesis of ‘difficult sequence‘ peptides. Herein, synthesis of three oligopeptides of different length, a pentapeptide Gly-Leu-Leu-Ser-Val, a heptapeptide fragment 285-291 of transmembrane (M7-24-T40) Ala-Val-Leu-Ser-Leu-Pro-Leu and a decapeptide, Gly- Leu-Leu-Ser-Val-Leu-Gly-Ser-Val-Ala were demonstrated in solution phase by employing O-acyl isopeptide method. The peptides were established through an efficient pH triggered intramolecular O→N acyl migration under physiological conditions. The reactions were clean and complete in appreciable length of time.

"Smart" peptides that lyse membranes in response to biological stimuli are of considerable interest. Herein, we report a facile synthesis of L-tetrafluorotyrosine (L-f(4)Y) and its utilization as a pH sensing element. The synthetic route affords gram quantities of L-f(4)Y within two days. Incorporation of this unnatural amino acid into magainin 2 gives a peptide that turns on its membrane-lytic activity upon mild acidification.

6 páginas, 5 figuras., Dimethylamino-functionalized fullerenes (pf-C60) have been used as removable “corks” at the openings of filled single-walled carbon nanotubes (SWCNTs). In a proof-of-principle study, SWCNTs have been filled with copper acetate or uranyl acetate, and these encapsulated materials then “corked” with pf-C60. The use of pf-C60 as “corks” allows the removal of the large amount of external acetate present after the filling step and a pH-triggered release of the encapsulated materials. A pH-sensitive discharge of the cargo would be of interest, for instance, in drug delivery systems., This research was supported in part by a Marie Curie European Reintegration Grant within the 7th European Community Framework Programme (PERG04-GA-2008-239303)(G.T.) and a Spanish Ministry of Science and Innovation contract (PTA2008-1108-I) (B.B.).

pH-dependent dimerization: Zwitterionic polyglycerol dendrons self-assemble into discrete and well-defined dimers in water as shown by dynamic light scattering (DLS), gel permeability chromatography (GPC), and DOSY NMR spectroscopy. However, self-assembly occurs only at neutral pH as either protonation or deprotonation destroys the self-complementary zwitterionic binding motif in the core of the dendrimer. Hence, structure formation can be triggered back and forth by changing the pH of the solution.

Water injection is commonly employed to increase the average reservoir pressure and displace the oil. However, water flooding is not always successful. The most important problem is channeling of the injected water into high permeability zones which occur in heterogeneous reservoirs. This is particularly true in naturally fractured reservoirs.Injecting low viscosity pH-triggered polymers into the reservoir to block the already swept fractures and high permeability zones is a promising solution. No injection of high viscosity gels or triggering agents is needed is this process. Polyacrylic acid microgels can swell a thousand fold as the pH of the surrounding solution changes, with an accompanying large increase in viscosity. In this paper we studied the factors affecting the feasibility and the placement of pH-triggered polymers into fractured reservoirs by performing several coreflood experiments in fractured cores.Polymer treatment reduced the overall core permeability in all cases in contact with different minerals in various sandstone and carbonate fractured cores. At polymer concentrations of 1% or greater, the permeability reduction was more than a factor of ten. The polymer microgels showed excellent consistency after being one month in reservoir condition at 58°C and resisted flow at pressure gradients up to 80 psi/ft. The selection of polymer and salt concentration in polymer solution depends on the application and desired PRF value. However, the 1% polymer concentration and 3% NaCl concentration is recommended due to the ease of polymer preparation, injectivity, reasonable geochemical buffering time and PRF values.

The effect of drug addition and pH variation on Pluronic copolymer solutions has been investigated using pulsed-field gradient (PFG) NMR. Addition of ibuprofen to Pluronic P104 in solution reduced the overall pH from 7.5 to 4.5, as well as promoting micellization; a substantial increase in the hydrodynamic radius of the micelles, from 57.7 to 102.3 A was observed, along with an increase in the fraction of polymer micellized. The aggregation behavior was attributed primarily to the presence of ibuprofen, rather than the reduction in pH observed, since the micellization of P104 alone was not found to be significantly altered by pH changes in the region of interest. Conversely, for the P104 solutions containing ibuprofen, a strong pH-dependence was observed when raising the pH above the pK(a) of ibuprofen. The data obtained showed that, above pH 4.5, ibuprofen is gradually released from the micelles as a result of its improved solubility, leading to a reduction in the polymer aggregation toward that observed before the addition of ibuprofen.

Water and gas shutoff in naturally fractured reservoirs is traditionally achieved with cross-linked gels. Low sweep efficiency is also an important problem in waterflooding such reservoirs which can be treated with gel. In-depth placement of gels is the key to success, and this requires careful control of the cross-linking chemistry. This work examines the feasibility of an alternative gelation mechanism in fractured rock: pH-triggered polymer microgels. The microgel particles are small enough to pass through fractures but not pore throats in a matrix. The pH change occurs naturally and inevitably; it thus offers a simpler means of obtaining deep placement.When an acidic polymer solution is injected into the formation, several factors affect the pH: rock mineralogy, reactive surface area of the minerals, temperature and dilution due to mixing with residual water. The viscosity of the solution depends strongly on pH and upon polymer concentration and salinity of the polymer solution. The rate of pH increase relative to the rate of fluid advance determines the depth of placement.We used commercially available polymers which exhibit low viscosity at a pH below 3 but transform to gels at pH > 4. Polymer solutions were injected through artificial fractures in outcrop cores. Both sandstone and carbonate rocks raise the polymer solution pH. The presence of acid-soluble minerals containing cations such as calcium can independently trigger viscosification by precipitating the polymer. After polymer injection, a shut-in time allows further reaction to increase the pH and thus affects the Permeability Reduction Factor (PRF), the ratio of original fractured core permeability to treated core permeability. The PRF was measured to be in the range of 200 to 5 during the various experiments. The gelation is faster and PRF is higher in carbonates than in sandstones. Because the neutralization capacity of a core is large, it is possible to approximate reactive transport in a reservoir by continuously re-circulating the polymer effluent. Experiments showed gellike characteristics after 30 pore volumes of recirculation in Berea sandstone.

The self-assembly of surfactant-protected gold nanorods (aspect ratio 3.3 +/- 0.3, 20.6 +/- 5.5 nm width, and 67.5 +/- 9.0 nm length) into ordered structures using adipic acid is presented. As made, the gold nanorods are coated with cationic surfactant, which gives them a net positive charge in aqueous solution. The pH-dependent assembly is directed by electrostatic interactions between the positively charged nanorods and negatively charged, deprotonated adipic acid. Absorption spectra and light scattering measurements of these nanorods suggest that aggregation is initiated in solution in the presence of adipic acid at pH 7-8, but not at pH 3, to form small assemblies of nanorods. Zeta potential measurements show that the assembly is significantly less positively charged in the presence of deprotonated adipic acid than when adipic acid is fully protonated.

A unique pH-driven Förster resonance energy transfer (FRET) based biosensor emission by a pyrazoline-doxorubicin pair has been deciphered with a bioimaging application in a live HepG2 cell whereas conformational switching of both molecules at elevated pH reveals a fascinating twist (FRET-OFF) via strong fluorescent exciplex formation.

Water-soluble gold nanorods have been endowed with satisfying chemical stability and functionality through successfully surface modifying with chemically reduced bovine serum albumin. A pH-induced ...

Wanted! A new lasso molecular shuttle was synthesized by a self-entanglement strategy. In their Full Paper on page 2982 ff., F. Coutrot et al. describe the efficient preparation of a new lasso molecular switch containing an anilinium template. Trapping of the BMP25C8 macrocycle was achieved by benzylation of the triazole moiety and allowed the isolation of a bi-stable lasso molecular switch, in which benzyltriazolium acts as a gate and a molecular station at the same time. Variation of pH triggered the tightening and loosening of the lasso.

Background: Peptide-based subunit vaccines require strong adjuvants (immunostimulant) for therapeutic potency. There is strong demand for the discovery of new safe adjuvants and vaccine delivery systems that

A crosslinked poly(N-isopropylacrylamide) ionogel encapsulating an ionic liquid exhibits improved transmittance properties, enhanced water uptake/release, greater thermal actuation behaviour and distinct solvatomorphology over its hydrogel equivalent. It was also found that the rate of release of fluorescein pre-loaded into membranes was considerably enhanced for ionogels compared to equivalent hydrogels, and could be triggered through changes in pH and temperature.

We report the fabrication of pH responsive switchable emulsions that quickly destabilise at acidic pH, but switch back to the stable state when the pH is neutralized. The pH triggered flocculation is further used to influence the assembly of droplets into predetermined shapes. Such systems, stabilised using natural and non-toxic components, can find important applications in the field of green colloidal structuring.

We report on two types of poly(methacrylic acid) (PMAA)-based hydrogel microcontainers (capsules) of cubical shape with distinctly different shape responses upon pH variations. The microcontainers were prepared as replicas of cubical inorganic templates through chemical cross-linking of hydrogen-bonded layer-by-layer (LbL) films. The two types of hollow hydrogels, a single-component (PMAA) and PMAA–poly(N-vinylpyrrolidone) (PMAA–PVPON), showed drastic differences in their shape response to pH variations. Cubical (PMAA)20 capsules turned into bulged sphere-like structures of the same size when transitioned from pH 3 to pH 8. In contrast, cubical (PMAA–PVPON)5 capsules retained their cubical shape at pH 3 while increasing in size at pH 8. The pH-triggered size change of cubical capsules was completely reversible. The difference in pH-triggered shape responses was rationalized through the difference in hydrogel rigidity expressed as the ratio of the polymer contour length between the neighboring cross-links to the persistence polymer length. The ratios of 22.7 and 2 for (PMAA) and (PMAA–PVPON) systems, respectively, suggested that the dual-component system is more rigid and therefore expands uniformly in all directions. We believe that the results provide new prospects for developing polymeric materials with predictable shape and size-changing properties for controlled drug delivery, cellular uptake, and pH-regulating transport behavior in microfluidic devices.

Iminodiacetate resorc[4]arene is shown to produce gels that are pH-reversible. The gels formed are clear and stable to inversion. (The gels are not stable above a certain temperature, which varies with concentration.) When the pH of an iminodiacetate resorc[4]arene solution (concentration >7.6 mM) is lowered to below 2.5, which is near one of the Ka values of the molecule, the dissolved molecules aggregate and cause gelation of water. 1H NMR showed that at the pH of gelation a change occurs in the chemical environment of the iminodiacetate group. Scanning electron microscopy showed that the gel is composed of long strands that interweave and create a molecular mesh.

Core cross-linked star polymers possessing responsiveness to pH and temperature stimuli have been prepared, and we demonstrate how changes to pH and temperature can be used to trigger the release and uptake of a hydrophobic dye.

The activities of Mg(2+)-dependent DNAzymes are reversibly switched by pH stimuli using the i-motif as an activating motif.

The present research work deals with the formulation and evaluation of in-situ gelling system based on sol-to-gel transition for ophthalmic delivery of an antibacterial agent gatifloxacin, to overcome the problems of poor bioavailability and therapeutic response exhibited by conventional formulations based a sol-to-gel transition in the cul-de-sac upon instillation. Carbopol 940 was used as the gelling agent in combination with HPMC and HPMC K15M which acted as a viscosity enhancing agent. The prepared formulations were evaluated for pH, clarity, drug content, gelling capacity, bioadhesive strength and in-vitro drug release. In-vitro drug release data of optimized formulation (F12) was treated according to Zero, First, Korsmeyer Peppas and Higuchi kinetics to access the mechanism of drug release. The clarity, pH, viscosity and drug content of the developed formulations were found in range 6.0-6.8, 10-570cps, 82-98% respectively. The gel provided sustained drug release over an 8 hour period. The developed formulation can be used as an in-situ gelling vehicle to enhance ocular bioavailability and the reduction in the frequency of instillation thereby resulting in better patient compliance. Key Words: In-situ gelation; Gatifloxacin; Carbopol 940; HPMC K15M. DOI: http://dx.doi.org/10.3329/icpj.v1i3.9661 International Current Pharmaceutical Journal 2012, 1(3): 43-49

The pH-triggered transitional phase behaviour of Pickering emulsions stabilised by hydrophobised bacterial cellulose (BC) is reported in this work. Neat BC was esterified with acetic (C2–), hexanoic (C6–) and dodecanoic (C12–) acids, respectively. We observed that C6– and C12–BC stabilised emulsions exhibited a pH-triggered reversible transitional phase separation. Water-in-toluene emulsions containing of 60vol.% dispersed phase stabilised by C6– and C12–BC were produced at pH 5. Lowering the pH of the aqueous phase to 1 did not affect the emulsion type. Increasing the pH to 14, however, caused the emulsions to phase separate. This phase separation was caused by electrostatic repulsion between modified BC due to dissociable acidic surface groups at high pH, which lowered the surface coverage of the water droplets by modified BC. When the pH was re-adjusted to 1 again, w/o emulsions re-formed for C6– and C12–BC stabilised emulsions. C2–BC stabilised emulsions, on the other hand, underwent an irreversible pH-triggered transitional phase separation and inversion. This difference in phase behaviour between C2–BC and C6–/C12–BC was attributed to the hydrolysis of the ester bonds of C2–BC at high pH. This hypothesis is in good agreement with the measured degree of surface substitution (DSS) of modified BC after the pH-triggered experiments. The DSS of C2–BC decreased by 20% whilst the DSS remained constant for C6– and C12–BC.

A cardiac pacemaker capable of responding to blood acidosis by change in its stimulation rate allows adjustment to a patient's metabolic needs. The blood pH is sensed by an iridium oxide electrode in the right atrium. During exercise, the venous pH decreases and the paced ventricular rate increases. If acidosis persists, the paced rate gradually returns to baseline and reaches it after about 70 minutes. A pH-triggered pacemaker has been implanted in a 72-year-old male. The pacemaker remained responsive one year after implant, increasing rate during exercise, cold pressor stress, ischemia of the arms and emotional stress.

Polymerisation rapide par ouverture de cycle du bromure de bis [lipoyloxy-11 undecyl] dimethylammonium, lorsque le pH de la dispersion se situe entre 3 et 4