Neutral Phosphate-buffered Saline Research Articles

Bioinspired Threonine-Based Polymers with Potent Ice Recrystallization Inhibition Activity.

Ice growth mitigation is a pervasive challenge for multiple industries. In nature, ice-binding proteins (IBPs) demonstrate potent ice growth prevention through ice recrystallization inhibition (IRI). However, IBPs are expensive, difficult to produce in large quantities, and exhibit minimal resilience to nonphysiological environmental stressors, such as pH. For these reasons, researchers have turned to bioinspired polymeric materials that mimic IBP behavior. To date, however, no synthetic polymer has rivaled the ability of native IBPs to display IRI activity at ultralow nanomolar concentrations. In this work, we study the IRI activity of peptides and polypeptides inspired by common ice-binding residues of IBPs to inform the synthesis and characterization of a potent bioinspired polymer that mimics IBP behavior. We show first that the threonine polypeptide (pThr) displays the best IRI activity in phosphate-buffered saline (PBS). Second, we use pThr as a molecular model to synthesize and test a bioinspired polymer, poly(2-hydroxypropyl methacrylamide) (pHPMA). We show that pHPMA exhibits potent IRI activity in neutral PBS at ultralow concentrations (0.01 mg/mL). pHPMA demonstrates potent IRI activity at low molecular weights (2.3 kDa), with improved activity at higher molecular weights (32.8 kDa). These results substantiate that pHPMA is a robust molecule that mitigates ice crystal growth at concentrations similar to native IBPs.

Triple-Function Au-Ag-Stuffed Nanopancakes for SERS Detection, Discrimination, and Inactivation of Multiple Bacteria.

New strategies combining sensitive pathogenic bacterial detection and high antimicrobial efficacy are urgently desirable. Here, we report smart triple-functional Au-Ag-stuffed nanopancakes (AAS-NPs) exhibiting (1) controllably oxidative Ag-etching thickness for simultaneously obtaining the best surface-enhanced Raman scattering (SERS) enhancement and high Ag-loading antibacterial drug delivery, (2) expressive Ag+-accelerated releasing capability under neutral phosphate-buffered saline (PBS) (pH ∼ 7.4) stimulus and robust antibacterial effectiveness involving sustainable Ag+ release, and (3) three-in-one features combining specific discrimination, sensitive detection, and inactivation of different pathogenic bacteria. Originally, AAS-NPs were synthesized by particle growth of the selective Ag-etched Au@Ag nanoparticles with K3[Fe(CN)6], followed by the formation of an unstable Prussian blue analogue for specifically binding with bacteria through the cyano group. Using specific bacterial "fingerprints" resulting from the introduction of dual-function 4-mercaptophenylboronic acid (4-MPBA, serving as both the SERS tag and internal standard) and a SERS sandwich nanostructure that was made of bacteria/SERS tags/AAS-NPs, three bacteria (E. coli, S. aureus, and P. aeruginosa) were highly sensitively discriminated and detected, with a limit of detection of 7 CFU mL-1. Meanwhile, AAS-NPs killed 99% of 1 × 105 CFU mL-1 bacteria within 60 min under PBS (pH ∼ 7.4) pretreatment. Antibacterial activities of PBS-stimulated AAS-NPs against S. aureus, E. coli, and P. aeruginosa were extraordinarily increased by 64-fold, 72-fold, and 72-fold versus PBS-untreated AAS-NPs, respectively. The multiple functions of PBS-stimulated AAS-NPs were validated by bacterial sensing, inactivation in human blood samples, and bacterial biofilm disruption. Our work exhibits an effective strategy for simultaneous bacterial sensing and inactivation.

Ocular Effects of Glycyrrhizin at Acidic and Neutral pH.

PurposeTo test the effects of acidic vs. neutral pH glycyrrhizin (GLY) on the unwounded and wounded normal mouse cornea and after infection with Pseudomonas aeruginosa isolates KEI 1025 and multidrug-resistant MDR9.MethodsAcidic or neutral GLY vs. phosphate-buffered saline (PBS) was topically applied to normal or wounded corneas of C57BL/6 mice. In unwounded corneas, goblet cells and corneal nerves were stained and quantitated. After wounding, corneas were fluorescein stained and photographed using a slit lamp. Mice also were infected with KEI 1025 or MDR9 and the protective effects of GLY pH evaluated comparatively.ResultsIn the unwounded cornea, application of acidic or neutral GLY vs. PBS reduced the number of bulbar conjunctival goblet cells but did not alter corneal nerve density. Similar application of GLY to scarified corneas delayed wound closure. After KEI 1025 infection, none of the GLY vs. PBS-treated corneas perforated; GLY treatment also decreased plate count (neutral pH more effective) and reduced MPO and several cytokines. Similarly, for MDR9, GLY at either pH was protective and also enhanced the effects of moxifloxacin to which MDR9 is resistant.ConclusionAcidic or neutral pH GLY decreased goblet cell number but had no effect on nerve density. After corneal wounding, GLY at either pH (1) delayed wound closure and, (2) after infection, decreased keratitis when used alone or in combination with moxifloxacin. Neutral pH did not alter the therapeutic effect of GLY and would be preferred if used clinically.

Glucose determination behaviour of gold microspheres-electrodeposited carbon cloth flexible electrodes in neutral media

Despite numerous advances in the field of nonenzymatic glucose detection, monitoring glucose in physiological applications is still a challenge and is mostly limited to electrode surface modification. This study proposes a simple method for electrodepositing cotton-like gold microspheres (CGMs) on a carbon cloth (CC) flexible electrode, with the potential for the functional supporting substrate to monitor glucose in a neutral environment. It was demonstrated that the voltammetric response of glucose oxidation increased with increases in glucose concentration in the 3D functional flexible substrate; moreover, the amperometric response of glucose oxidation increased over time. The results indicate that the functional flexible electrode—made of gold microspheres-based carbon cloth with a predefined geometry and pore-architecture network to promote the medium-permeation and synergetic effects between CGMs and CC—can be a suitable platform for measuring glucose variation in environments with neutral pH. This is particularly relevant because the oxygen-containing functional groups on the CC surface increase the dehydrogenation rate of glucose oxidation in neutral phosphate-buffered saline.

Metal-Phenolic Network-Encapsulated Nanovaccine with pH and Reduction Dual Responsiveness for Enhanced Cancer Immunotherapy.

Cancer nanovaccines have been widely explored to enhance immunotherapy efficiency, in which the significant irritation of antigen-specific cytotoxic T cells (CTLs) is the critical point. In this study, we developed a pH and reduction dual-sensitive nanovaccine (PMSN@OVA-MPN) composed of two parts. The inner part was made up of polyethyleneimine (PEI)-modified mesoporous silica nanoparticles (MSNs) loaded with model antigen ovalbumin (OVA) and the outer part was made up of disulfide bond-involved metal-phenolic networks (MPNs) as a protective corona. In vitro release experiments proved that PMSN@OVA-MPN could intelligently release OVA in the presence of reductive glutathione, but not in neutral phosphate-buffered saline (PBS). Moreover, in vitro cell assays indicated that the nanovaccine promoted not only the OVA uptake efficiency by DC2.4 cells but also antigen lysosome escape due to the proton sponge effect of PEI. Furthermore, in vivo animal experiments indicated that PMSN@OVA-MPN induced a large tumor-specific cellular immune response so as to effectively inhibit the growth of an existing tumor. Finally, the immune memory effect caused by the nanovaccine afforded conspicuous prophylaxis efficacy in neonatal tumors. Hence, the multifunctional vaccine delivery system prepared in this work exhibits a great application potential in cancer immunotherapy and offers a platform for the development of nanovaccines.

Calcium-siRNA Nanocomplexes Optimized by Bovine Serum Albumin Coating Can Achieve Convenient and Efficient siRNA Delivery for Periodontitis Therapy.

PurposeReducing toxicity, immunogenicity, and costs of small interfering RNAs (siRNA) carrier materials are key goals for RNA interference (RNAi) technology transition from bench to bed. Recently, calcium ions (Ca2+) have garnered attention as a novel, alternative material for delivering siRNA to cells. However, the tolerance for Ca2+ concentration varies in different cell types, which has limited its applications in vivo. Bovine serum albumin (BSA) can bind to Ca2+ through chelation. Moreover, BSA is a favorable coating material for nanoparticles owing to its excellent biocompatibility. Therefore, we hypothesized that coating Ca2+-siRNA with BSA helps buffer Ca2+ toxicity in vivo.MethodsBSA-Ca2+-siRNA nanoparticles were prepared, and the size, shape, encapsulation, and release efficiency were characterized using atomic force microscopy, scanning electronic microcopy, and gel electrophoresis. Binding nanoparticles were evaluated using attenuated total reflection-Fourier-transform infrared spectroscopy. The cellular uptake, intracellular release, cytotoxicity, and gene knockdown of nanoparticles were evaluated in periodontal ligament stem cells (PDLSCs) using laser-scanning confocal microscope, flow cytometry, and real-time quantitative polymerase chain reaction.ResultsBSA and Ca2+-siRNA could form a stable nano-scale complex (~140 nm in diameter). The nanocomplexes could maintain siRNA release for more than 1 week in neutral phosphate-buffered saline (PBS) and could induce accelerated degradation in acidic PBS (pH 5.0). The nanoparticles were taken up by the cells, primarily through macropinocytosis, and were then released intracellularly through the acidification of endosomes/lysosomes. Importantly, the BSA-Ca2+ carrier had high transfection efficiency and biocompatibility both in vitro and in vivo. To demonstrate the therapeutic potential of our BSA coating-optimized Ca2+-siRNA technology, we showed that BSA-Ca2+-siWWP1 complexes strongly enhanced the osteogenic differentiation of inflammatory PDLSCs.ConclusionBSA-Ca2+ could potentially be used for siRNA delivery, which is not only highly efficient and cost-effective but also biocompatible to host tissues owing to the BSA coating.

Experimental data and modeling of electrical conductivity for polymer carbon nanotubes nanobiosensor during degradation in neutral phosphate-buffered saline (PBS)

This paper studies the conductivity of poly (lactic acid) (PLA)/poly (ethylene oxide) (PEO)/carbon nanotubes (CNT) nanocomposites during degradation in neutral phosphate-buffered saline (PBS) solution by experimental and modeling results. PLA/PEO/CNT nanocomposites are prepared and the conductivity of samples is measured before and during degradation. This system can be applied as a degradation nanobiosensor, because the variation of conductivity expresses the extent of degradation. A simple model is developed to predict the variation of conductivity during hydrolytic degradation. The degradation of polymers improves the effectiveness of CNT networks in the samples growing the conductivity. The proper agreement between experimental and theoretical results approves the validity of the developed model. A longer degradation time destroys more polymer chains shortening the tunneling space between CNT. The percolation threshold increases during degradation, due to the degradation of interphase zones between polymer and CNT. The calculations demonstrate that the fraction of networked CNT decreases during degradation, because PBS solution attacks the CNT networks. These reasonable predictions validate the developed equations representing the variations of conductivity, tunneling distance, percolation threshold and the fraction of networked CNT in the samples during degradation.

Simple model for hydrolytic degradation of poly(lactic acid)/poly(ethylene oxide)/carbon nanotubes nanobiosensor in neutral phosphate-buffered saline solution.

In this study, the hydrolytic degradation of poly(lactic acid) (PLA)/poly(ethylene oxide) (PEO) blend and PLA/PEO/carbon nanotubes (CNTs) nanobiosensors in neutral phosphate-buffered saline (PBS) solution was investigated by experimental and theoretical approaches. A simple model was developed to estimate the degradation fraction by applying the average degradation rate (K) and time exponent. The predictions of the developed model were compared to the experimental results. Moreover, CNT concentration, CNT size, sample thickness, diffusion coefficient, and concentration of the PEO phase influenced the K value. The impacts of the parameters on the degradation rate were studied to confirm the developed equation. All samples were rapidly degraded during the first week, while the degradation slowly progressed in the following weeks. The experimental and theoretical results demonstrate that CNTs quicken the degradation of samples. The degradation fraction of a nanobiosensor depends directly on the values of K and the time exponent. Furthermore, a high concentration of PEO, small thickness of the sample, high concentration of thin CNTs, and high diffusion coefficient desirably improve the degradation rate.

Following the morphological and thermal properties of PLA/PEO blends containing carbon nanotubes (CNTs) during hydrolytic degradation

In this article, the morphology, melting behavior, crystallinity and thermal stability of poly (lactic acid) (PLA)/poly (ethylene oxide) (PEO) blends and PLA/PEO/carbon nanotubes (CNTs) nanocomposites are studied before and after the hydrolytic degradation in neutral phosphate-buffered saline (PBS) solution. The morphologies of all the samples show PEO droplets in a continuous PLA phase, but the addition of CNTs to the blends diminishes the size of the PEO particles and homogenizes their dispersion before and after degradation. Additionally, the degradation did not change the morphologies of the samples. The samples showed two different melting peaks, indicating that the PLA/PEO blend is not miscible. The low crystallinity of PLA in the degraded samples was due to the short chains and high cold crystallization. The thermal decomposition of the samples occurred in two stages, demonstrating the poorer thermal stability of PLA compared to PEO. The positive and negative roles of CNTs in the thermal stability depend on the concentrations of PLA and CNTs, which determine the protective role or heat transfer of CNTs in the samples.

Degradation biosensing performance of polymer blend carbon nanotubes (CNTs) nanocomposites

This paper describes the hydrolytic degradation and sensing behavior of poly (lactic acid) (PLA)/poly (ethylene oxide) (PEO)/carbon nanotubes (CNTs) nanocomposites in neutral phosphate-buffered saline (PBS) solution. Degradation sensing is performed based on the variations of electrical conductivity due to the degradation of PLA and PEO phases. The molecular weights of polymers, the morphologies of polymer blends and nanocomposites, the chemical bonds and the crystalline structures of polymers are analyzed before and during the degradation process. CNTs promote the degradation of PLA/PEO blends and the conductivity of all samples improves with increased degradation time. The samples with high PEO and CNTs concentrations exhibit a considerable sensing, because they show a large variation in conductivity during degradation. A matrix-droplet structure forms in the samples before and after degradation, where PEO particles are dispersed in a continuous PLA phase. Both amorphous and crystalline regions of PEO experience the hydrolytic degradation, but CNTs largely control the crystallinity of PLA suggesting the localization of CNTs in the PLA phase.

Wireless Magnetoelasticity-Based Sensor for Monitoring the Degradation Behavior of Polylactic Acid Artificial Bone In Vitro

A magnetoelasticity-based (MB) sensor was employed for monitoring the degradation behavior of polylactic acid (PLA) artificial bone (PAB) in vitro, which can be used as an implant to repair bone defects. Biodegradable PLA material was coated on both sides of the MB sensor strip with a 3D printer, forming PAB. The PAB samples were submerged in an alkaline medium (pH = 12) and a neutral phosphate-buffered saline (PBS) medium (pH = 7.4). The degradation behavior of the PAB was monitored wirelessly based on changes in the output power of the MB sensor. The results indicated that the output power varied by almost 0.2 and 0.11 dbm over 15 days in the two media. The degradation behavior monitored by the MB sensor agreed with the theoretical analysis. The MB sensor provides a wireless method for monitoring the degradation behavior of PAB in vitro and requires few samples at a lower cost. Importantly, the results showed that biological tissues had almost no effect on the monitoring function of the MB sensor. Therefore, the MB sensor technology is highly attractive for fully characterizing the degradation behavior of bone implants in a larger range of physiological conditions, and will be applied to monitor the degradation behavior in vivo.

Incorporation of osteogenic and angiogenic small interfering RNAs into chitosan sponge for bone tissue engineering.

Engineered bone substitutes are being extensively explored in response to growing demand. However, the angiogenesis that occurs during bone formation is often overlooked in scaffold design. In this novel study, we incorporated two small interfering RNAs (siRNAs), ie, small interfering RNA targets casein kinase 2 interaction protein 1 (siCkip-1) and small interfering RNA targets soluble VEGF receptor 1 (siFlt-1), which can promote osteogenesis and angiogenesis, into a chitosan sponge. This scaffold could maintain siRNAs for over 2 weeks in neutral phosphate-buffered saline and degraded rapidly in the presence of lysozyme. The chitosan sponge with siCkip-1 and siFlt-1 in vitro bioactivity was investigated using mesenchymal stem cells. Target genes were significantly suppressed, and osteocalcin, alkaline phosphatase, and vascular endothelial growth factor were significantly upregulated. Alizarin Red staining revealed that mineralization of the extracellular matrix was markedly enhanced by dual transfection. Further analysis by immunofluorescence confirmed that the siRNA-modified scaffold simultaneously improved the expression of osteocalcin and von Willebrand factor. In vivo testing in a skull critical-size defect model showed marked bone regeneration in rats treated with siCkip-1 and siFlt-1. In conclusion, chitosan sponge containing osteogenic and angiogenic siRNAs may be used as a scaffold for bone regeneration. The dual siRNA concept may also be useful in the biofunctionalization of other materials.

Electrochemically Fabricated Pyrrole Copolymer Thin Films and Their Electroactivity in Neutral Aqueous Solution

The functionalized pyrrole copolymers were fabricated by electropolymerization of pyrrole (Py) and functionalized pyrrole monomers, pyrrole-3-carboxylic acid (P3C) and 4-(3-pyrrole) butyric acid (PBA). The electrochemical behavior and doping/dedoping properties of the obtained copolymer thin films were investigated by cyclic voltammetry (CV) in neutral phosphate-buffered saline (PBS) solution. Moreover, the functionalized pyrrole copolymer films were characterized by UV-vis absorption spectroscopy and atomic force microscopy (AFM). The obtained copolymer thin films showed good stability and electroactivity in neutral PBS solution. The presented functionalized pyrrole copolymer thin films may possess potential applications to study in various systems of the biosensors.

Inactivation behavior of Pseudomonas aeruginosa by supercritical N2O compared to supercritical CO2

Interest is growing for a non-thermal sterilization technique in the food and pharmaceutical industries in order to ensure microbiological safety without the deterioration of product quality. In this study, supercritical nitrous oxide (SC N2O) treatment was carried out in a multi-batch system to examine its bactericidal effect and characteristics, which largely remains unclear. The effect of operating pressure, temperature, mixing intensity, and working volume ratio (defined as the ratio of sample volume to the reactor volume to be filled with SC fluids) on the inactivation efficiency of SC N2O were investigated in comparison with supercritical carbon dioxide (SC CO2) treatment. Pseudomonas aeruginosa was chosen as a model microorganism. A 8-log reduction of P. aeruginosa cell concentration (10% working volume) in neutral phosphate-buffered saline was achieved by the SC N2O treatment accompanying no pH change in the presence of vigorous mixing (600rpm) within 6min, in a condition of 37°C and 10MPa and its overall efficiency is comparable to the SC CO2 treatment. Among the reaction parameters investigated in this study, mixing intensity appeared to be the most important operating parameter affecting the bactericidal efficiency.The release of intracellular substances in cells as a result of the SC N2O treatment was explained as one of major bactericidal actions by the SC N2O treatment. At the same time, relatively negligible change of proteins or enzyme activities in the cells in case of the SC N2O treatment was observed compared to the SC CO2 treatment. Also, the observation by scanning and transmission electron microscopy shows the milder morphological change of SC N2O-treated cells in comparison with the SC CO2-treated cells. This study suggests that the SC N2O bactericidal application on food products would be a viable option over SC CO2 application, when mild change of enzyme activity and the proteins, or no pH change are desired.

Electrochemically controlled surface plasmon resonance immunosensor for the detection of human immunoglobulin G on poly(3-aminobenzoic acid) ultrathin films

An electrochemically controlled surface plasmon resonance (SPR) immunosensor based on carboxylated polyaniline was constructed for detecting human immunoglobulin G (IgG) without using further labeled molecules. The carboxylated polyaniline, poly(3-aminobenzoic acid) (PABA), was prepared by electropolymerization of its monomer, 3-aminobenzoic acid (ABA), on a gold-coated high-refractive-index glass slide that was also used as a working electrode for the electrochemical system. The kinetic properties during electropolymerization were monitored in situ with electrochemical-surface plasmon resonance (EC-SPR) spectroscopy. The obtained PABA film, which was used to construct the immunosensor, showed electroactivity in neutral phosphate-buffered saline solution. The carboxylic acid surface of the PABA film was then activated to immobilize anti-human IgG. Finally, the immunosensor electrode was used to probe the binding reaction of anti-human/human IgG with various concentrations of human IgG at different constant applied potentials. The immobilization and binding reaction processes were controlled and also studied in situ by EC-SPR spectroscopy. The binding process at different applied potentials was studied and fitted using the Freundlich model. The surface morphology of the films after the immobilization of anti-human IgG was studied by atomic force microscopy.

Hydrophobicity predicts in vivo 19F magnetic resonance detectability of fluorinated psychiatric drugs: simple test for likely success in clinical pharmacokinetic studies

AbstractThe 19F NMR signal half‐height linewidths of six fluorinated psychiatric pharmaceuticals, on which successful in vivo magnetic resonance (MR) studies have been reported (fenfluramine, fluvoxamine, fluoxetine, trifluoperazine, phenfluramine, and paroxetine), were measured at 0.3 mM concentration in an artificial biofluid consisting of aqueous isotonic neutral phosphate‐buffered saline and 5% w/v bovine serum albumin. For the first five, which contain trifluoromethyl groups, linewidth is strongly positively correlated (R2=0.95) with calculated water: n‐octanol distribution coefficient at pH7 (cLogDpH7) by the relationship: Linewidth (Hz)=38cLogDpH7+5. This suggests that simple measurements, or calculations, feasible in most chemical laboratories, predict in vivo signal linewidth and hence the likely ease with which a development compound would be detected in clinical trials of brain pharmacokinetics. The procedures are available to all drug development organizations and should help establish confidence, or no‐go decisions, about committing major resources to MR pharmacokinetic studies on human subjects. Drug Dev Res 69:279–283, 2008 © 2008 Wiley‐Liss, Inc.

Ascorbic Acid as a Free Radical Scavenger in Porcine and Bovine Aqueous Humour

Aim: To study the antioxidant activity, UV absorption, concentration and stability of ascorbic acid (AA) in porcine and bovine aqueous humour (AH). Methods: Porcine and bovine AH was taken within 5 min after death and frozen at –70°C. The characteristic UV absorption band of AA and the concentration of AA in AH was determined by UV spectrophotometry. The antioxidant activity of AA to serve as a free radical scavenger in AH has been determined by using a novel fluorescent probe for antioxidants, the azoalkane 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO). The fluorescence lifetime and intensity of this probe reflect the concentration of dissolved antioxidants. The time-resolved fluorescence of DBO (laser excitation at 351 nm) in AH and in a neutral phosphate-buffered saline (PBS) solution containing only the natural amount of AA as an additive were measured. Results: The characteristic UV absorption band of AA has its maximum at 266 nm in AH. The concentration of AA in porcine and bovine AH was found to be 0.547 ± 0.044 and 1.09 ± 0.16 mM, respectively, by spectrophotometry. The fluorescence lifetime of the probe DBO was reduced from 320 ± 5 ns in pure aerated PBS to 205 ± 5 ns in porcine AH and 165 ± 3 ns in bovine AH. A detailed kinetic analysis of the lifetime shortening suggests that AA contributes approximately 75 and 85% to the antioxidant activity of porcine and bovine AH, respectively. Conclusions: Our experiments suggest that AA is the major contributor to the antioxidant activity of porcine and bovine AH. The role of AA to serve as an antioxidant in AH is discussed. In addition, UV spectrophotometry is established as an alternative method to determine the concentration of AA in AH.

Round window pH manipulation alters the ototoxicity of systemic cisplatin

The effect of manipulation of pH on the ototoxicity of systemic cisplatin was studied in Wistar rats. After control auditory brainstem responses (ABR) were performed, the auditory bullae were opened and acidic (pH 6.0), neutral (pH 7.4) or basic (pH 9.0) phosphate-buffered saline (PBS) was applied to fill the round window niche (RWN). After 30 min, 13 mg/kg cisplatin solution or saline was administered intraperitoneally. After 3 days, follow-up ABRs were performed and cochleae were processed for morphological analysis. Animals that received basic PBS on the RWN and cisplatin intraperitoneally had significantly smaller ABR threshold shifts compared to rats pretreated with neutral pH buffer ( P<0.05). Animals that received acidic PBS on the RWN and systemic cisplatin showed significantly greater ABR threshold shifts compared to those pretreated with neutral pH buffer ( P<0.05). No significant threshold changes were observed in animals that received buffer of any pH on the RWN, followed by saline intraperitoneally. Semiquantitative analysis of hair cell survival confirmed a protective effect by basic PBS against cisplatin and a synergistic effect by acidic PBS on cisplatin ototoxicity ( P<0.05). It appears that changes in cochlear pH can modulate the ototoxic effects of systemically applied cisplatin.

Influence of pH on the ototoxicity of cisplatin: a round window application study

Cisplatin is an antineoplastic agent that produces a number of dose-limiting side effects, including ototoxicity. We investigated the effect of pH on cisplatin ototoxicity. Auditory brainstem responses (ABR) were recorded in chinchillas. Then the auditory bullae were opened and acidic (pH=6.5), neutral (pH=7.4) or alkaline (pH=10.2) phosphate-buffered saline (PBS) was applied to the round window membrane. After 30 min, any remaining solution was removed and cisplatin solution was applied to the round window membrane. After 3 days, follow-up ABRs were performed and the cochleae were processed for morphological analysis. Neutral PBS+cisplatin administration resulted in profound threshold changes at all frequencies. Acidic PBS+cisplatin administration showed had a trend of increased threshold changes, but the change did not reach statistical significance. However, the degree of hair cell loss was significantly higher than that of the neutral PBS-cisplatin group. Alkaline PBS significantly reduced cisplatin-induced threshold changes ( P<0.05) compared to the neutral PBS group. Because the pH of cisplatin solution was 6.0, pH 6.0 PBS was applied to round window membrane. This acidic PBS solution did not cause any hearing impairment. These results demonstrate that pH can modulate the ototoxic effects of cisplatin.

Incorporation of bovine serum albumin in calcium phosphate coating on titanium.

Calcium phosphate (Ca-P) and bovine serum albumin (BSA) were coprecipitated as a coating on commercially pure titanium (cpTi) with a high protein loading (15 wt %) by employing a recently developed wet-chemistry technique. It was observed that the incorporation of BSA significantly modified the morphology, composition, and crystallinity of the Ca-P coating. The Ca-P coating without BSA is a mixture of hydroxyapatite (HA) and octacalcium phosphate (OCP) with sharp-edged thin OCP crystal plates on the top layer, whereas only an HA phase was detected in the Ca-P/BSA coating. The crystal plates in the latter had a more rounded appearance. The Ca-P/BSA coatings were immersed respectively in neutral (pH 7.4) and acidic (starting pH 4.0) phosphate-buffered saline (PBS) at 37 degrees C over a 14-day period. No protein release was detected in the neutral PBS during the immersion; however, a continuous release of BSA was measured in the acidic PBS, subsequently leading to the formation of a very dense and well-adherent composite coating of BSA and Ca-P on cpTi. The present study provides the possibility to achieve a long-term effective release of biologically active proteins from a Ca-P-coated metallic implant.