Acidity Is an Excellent Marker of Infection in Hip and Knee Arthroplasty.

BACKGROUND: The diagnosis of joint replacement infection is a difficult clinical challenge that often occurs when the implant cannot be salvaged. We hypothesize that the pH value of synovial fluid could be an important indicator of the inflammatory status of the joint. However, in the literature, there is a lack of data on the pH changes in hip and knee joint replacements and their relation to infection and implant failure. In this study, we aimed to measure the pH levels of synovial fluid in patients with hip and knee joint replacements. We also investigated the potential of pH measurement as a diagnostic tool for joint replacement infection. In this study, we recorded the pH values to be 7.55 and 7.46 in patients where Pseudomonas aeruginosa was identified as the cause of the prosthetic joint infection. We attribute this to the different environments created by this specific bacterium. In other cases where the pH was higher, chronic mitigated infections were diagnosed, caused by strains of Staphylococcus aureus, Streptococcus agalactiase, and coagulase negative staphylococcus. MATERIALS AND METHODS: In our cohort of 155 patients with implanted hip (THA; n = 85) or knee (TKA; n = 70) joint replacements, we conducted a prospective study with a pH measurement. Out of the whole cohort, 44 patients had confirmed joint replacement infection (28.4%) (44/155). In 111 patients, infection was ruled out (71.6%) (111/155). Joint replacement infection was classified according to the criteria of the Musculoskeletal Infection Society (MSIS) from 2018. Based on the measured values, we determined the cut-off level for the probability of ongoing inflammation. We also determined the sensitivity and specificity of the measurement. RESULTS: The group of patients with infection (n = 44) had a significantly lower synovial fluid pH (pH = 6.98 ± 0.48) than the group of patients with no infection (n = 111, pH = 7.82 ± 0.29, p < 0.001). The corresponding median pH values were 7.08 for the patients with infection and 7.83 for the patients with no infection. When we determined the cut-off level of pH 7.4, the sensitivity level of infected replacements was 88.6%, and the specificity level of the measurement was 95.5%. The predictive value of a positive test was 88.6%, and the predictive value of a negative test was 95.5%. CONCLUSIONS: Our results confirm that it is appropriate to include a pH measurement in the diagnostic spectrum of hip and knee replacements. This diagnostic approach has the potential to provide continuous in vivo feedback, facilitated by specialized biosensors. The advantage of this method is the future incorporation of a pH-detecting sensor into intelligent knee and hip replacements that will assess pH levels over time. By integrating these biosensors into intelligent implants, the early detection of joint replacement infections could be achieved, enhancing proactive intervention strategies.

A New Method to Prepare Stable Polyaniline Dispersions for Highly Loaded Cathodes of All-Polymer Li-Ion Batteries.

A new method for the preparation of polyaniline (PANI) films that have a 2D structure and can record high active mass loading (up to 30 mg cm-2) via acid-assisted polymerization in the presence of concentrated formic acid was developed. This new approach represents a simple reaction pathway that proceeds quickly at room temperature in quantitative isolated yield with the absence of any byproducts and leads to the formation of a stable suspension that can be stored for a prolonged time without sedimentation. The observed stability was explained by two factors: (a) the small size of the obtained rod-like particles (50 nm) and (b) the change of the surface of colloidal PANI particles to a positively charged form by protonation with concentrated formic acid. The films cast from the concentrated suspension were composed of amorphous PANI chains assembled into 2D structures with nanofibrillar morphology. Such PANI films demonstrated fast and efficient diffusion of the ions in liquid electrolyte and showed a pair of revisable oxidation and reduction peaks in cyclic voltammetry. Furthermore, owing to the high mass loading, specific morphology, and porosity, the synthesized polyaniline film was impregnated by a single-ion conducting polyelectrolyte-poly(LiMn-r-PEGMm) and characterized as a novel lightweight all-polymeric cathode material for solid-state Li batteries by cyclic voltammetry and electrochemical impedance spectroscopy techniques.

Hydrophilic polyelectrolyte microspheres as a template for poly(3,4-ethylenedioxythiophene) synthesis.

Conducting polymer polyelectrolyte microspheres are typically composed of a cationic conducting polymer and an anionic polymer. The polymer chains inside these microspheres are physically or chemically cross-linked, creating a network that enables high water retention. Poly(3,4-ethylenedioxythiophene) (PEDOT) being an electrically conductive polymer exhibits a high conductivity and has great biotechnological applications. The unique combination of properties of PEDOT containing polyelectrolyte microspheres makes them widely investigated materials for electroresponsive cells, tissue engineering, and bio-sensors. The demand to produce PEDOT with varied properties depending the specific application requires the understanding of the basic principles of template formation. In the present work, we studied the inverse suspension polymerization of p-styrenesulfonic acid in the presence of a cross-linking agent as a synthetic way for the formation of porous polyelectrolyte microspheres. We traced how the nature of the emulsifier affected both the structure of the surface layer of the microspheres and the degree of their cross-linking. The porous structure of polyelectrolyte microspheres obtained is found to promote the polymerization of EDOT in their presence throughout the entire microsphere volume. The structural characteristics of the polyelectrolyte/PEDOT complexes in relation to their electrochemical properties have been studied.

Acid-assisted polymerization: the novel synthetic route of sensing layers based on PANI films and chelating agents protected by non-biofouling layer for Fe2+ or Fe3+ potentiometric detection.

A new synthetic method for the fabrication of a sensing layer is presented. PANI films as an ion-to-electron transducer were prepared via acid-assisted polymerization in concentrated formic acid (HCOOH) in the presence of ethanol and ammonium persulfate (APS, as the initiator). The ratio of monomer to ammonium persulfate was 1 : 0.1. 2,2-Bipyridyl, 1,10-phenanthrolin-5-amine, and 8-hydroxyquinoline were used as chelating agents that can complex Fe2+ or Fe3+ ions. The proposed sensors demonstrated an appropriate reproducibility with a rapid response to the presence of Fe2+ or Fe3+ ions, even at T ∼ 37 °C. It was revealed that the method of deposition of a chelating molecule affects the response of sensors. The in situ deposition during acid-assisted polymerization leads to a fast response compared to the layer-by-layer deposition. PMeOx/X1-PANI@FTO and PMeOx/Z1-PANI@FTO sensors exhibit rapid response and are considered a promising detection layer for Fe2+ or Fe3+ ions respectively. We envision that this system can contribute to the next generation of advanced bio-sensors for the potentiometric detection of iron.

Influence of the Nature and Structure of Polyelectrolyte Cryogels on the Polymerization of (3,4-Ethylenedioxythiophene) and Spectroscopic Characterization of the Composites.

Conductive hydrogels are polymeric materials that are promising for bioelectronic applications. In the present study, a complex based on sulfonic cryogels and poly(3,4-ethylenedioxythiophene) (PEDOT) was investigated as an example of a conductive hydrogel. Preparation of polyacrylate cryogels of various morphologies was carried out by cryotropic gelation of 3-sulfopropyl methacrylate and sulfobetaine methacrylate in the presence of functional comonomers (2-hydroxyethyl methacrylate and vinyl acetate). Polymerization of 3,4-ethylenedioxythiophene in the presence of several of the above cryogels occurred throughout the entire volume of each polyelectrolyte cryogel because of its porous structure. Structural features of cryogel@PEDOT complexes in relation to their electrochemical properties were investigated. It was shown that poly(3,4-ethylenedioxythiophene) of a linear conformation was formed in the presence of a cryogel based on sulfobetaine methacrylate, while minimum values of charge-transfer resistance were observed in those complexes, and electrochemical properties of the complexes did not depend on diffusion processes.

Potentiometric Performance of Ion-Selective Electrodes Based on Polyaniline and Chelating Agents: Detection of Fe2+ or Fe3+ Ions.

We constructed a sensor for the determination of Fe2+ and/or Fe3+ ions that consists of a polyaniline layer as an ion-to-electron transducer; on top of it, chelating molecules are deposited (which can selectively chelate specific ions) and protected with a non-biofouling poly(2-methyl-2-oxazoline)s layer. We have shown that our potentiometric sensing layers show a rapid response to the presence of Fe2+ or Fe3+ ions, do not experience interference with other ions (such as Cu2+), and work in a biological environment in the presence of bovine serum albumin (as a model serum protein). The sensing layers detect iron ions in the concentration range from 5 nM to 50 µM.

Preparation of Smart Surfaces Based on PNaSS@PEDOT Microspheres: Testing of E. coli Detection.

The main task of the research is to acquire fundamental knowledge about the effect of polymer structure on the physicochemical properties of films. A novel meta-material that can be used in manufacturing sensor layers was developed as a model. At the first stage, poly(sodium 4-styrenesulfonate) (PNaSS) cross-linked microspheres are synthesized (which are based on strong polyelectrolytes containing sulfo groups in each monomer unit), and at the second stage, PNaSS@PEDOT microspheres are formed. The poly(3,4-ethylenedioxythiophene) (PEDOT) shell was obtained by the acid-assisted self-polymerization of the monomer; this process is biologically safe and thus suitable for biomedical applications. The suitability of electrochemical impedance spectroscopy for E. coli detection was tested; it was revealed that the attached bacterial wall was destroyed upon application of constant oxidation potential (higher than 0.5 V), which makes the PNaSS@PEDOT microsphere particles promising materials for the development of antifouling coatings. Furthermore, under open-circuit conditions, the walls of E. coli bacteria were not destroyed, which opens up the possibility of employing such meta-materials as sensor films. Scanning electron microscopy, X-ray photoelectron spectroscopy, water contact angle, and wide-angle X-ray diffraction methods were applied in order to characterize the PNaSS@PEDOT films.

Cross-linked polyelectrolyte microspheres: preparation and new insights into electro-surface properties.

Polyelectrolyte microspheres find applications in many fields such as ion exchange columns, fuel cell membranes, and catalysis, to name a few. Synthesis of these microspheres by inverse emulsion polymerization offers various advantages due to the increased specific surface area and high surface charge density. The surface charge density of the obtained polyelectrolyte microspheres is a hundred times higher than that of either particles obtained by dispersion copolymerization of styrene and styrenesulfonic acid or sulfonated microspheres. The morphology, chemical structure, and electro-surface properties of the synthesized microspheres were studied by transmission and scanning electron microscopy, FTIR-spectroscopy, and conductometric and potentiometric titrations, respectively. Using the potentiometric titration it is possible to characterize the structure of the surface layer of polyelectrolyte microspheres as entirely as possible. The study of the ion-exchange capacity of polyelectrolyte microspheres shows that ion-exchange capacity is 2.1 meq g-1 in this case, which is more than 2 times higher than that of sulfonated microspheres, and 20 times higher than that of particles obtained by dispersion copolymerization.

Electrochemical deposition of highly hydrophobic perfluorinated polyaniline film for biosensor applications.

Highly hydrophobic perfluorinated polyaniline thin films with water contact angle of ∼140° and low internal resistance properties are prepared through electrochemical polymerization. UV-visible spectroscopy demonstrates a gradual evolution of the polaron band which indicates the electronic conductive properties of the polymers. Simultaneous possession of the water-repelling property and electron conductivity for superhydrophobic perfluorinated polyaniline leads to a unique polymer that is suitable as a solid contact in ion-selective electrodes for in situ monitoring of pH changes during early stages of inflammation and septic shock. The superhydrophobic properties should suppress interactions with interfering salts and proteins, and the sensitivity towards protons could be monitored by measuring the phase boundary potential, which depends on the H+ concentration. The potentiometric measurements demonstrate a fast response with a slope of 44.4 ± 0.2 mV per unit pH. The presence of interfering ions and/or human serum albumin does not have any significant effect on the performance of the perfluorinated film. Moreover, it is demonstrated that the response of the perfluorinated film is reversible within the biomedically relevant pH range from 4.0 to 8.5, and stable over time.

Water in Ionic Liquids: Correlation between Anion Hydrophilicity and Near-Infrared Fingerprints.

We show that fingerprints of the different states of water association can be clearly distinguished in the range of the first overtone of water's symmetric O-H stretching in the spectra of water-saturated [EMIm](+) -based ionic liquids with anions of substantially different hydrophilicity, such as hydrophobic [(CF3 SO2 )2 N](-) , moderately hydrophilic [CF3 SO3 ](-) , and highly hydrophilic [HSO4 ](-) .

J-like liquid-crystalline and crystalline states of polyaniline revealed by thin, highly crystalline, and strongly oriented films.

Liquid-crystalline state of dyes can be easy distinguished from the crystalline one by the appearance of characteristic long-wavelength optical absorption, the so-called J-band. Similarly, long-wavelength absorption of polyaniline is assumed to be the signature of its J-like liquid-crystalline state. When water evaporates from polyaniline adsorbed on a glass support during polymerization, the long-wavelength maximum at about 800 nm disappears, and one at 570 nm appears, characteristic for highly crystalline and strongly oriented thin film. Reversible red shift of long-wavelength absorption upon water adsorption is a significant feature of these films. By analogy with dyes, it is attributed to water-promoted superficial formation of J-like mesophase. Such surprising properties of wet films as propagation of chemical reduction and enhanced exciton transport, reported by us recently, can also be considered as a signature of the J-like liquid-crystalline state of polyaniline.

Self-assembly of aniline oligomers.

A great number of nano/microscaled morphologies have recently been prepared during the oxidation of aniline. At the early stage of oxidation, aniline oligomers are obtained, often in spectacular morphologies depending on reaction conditions. Herein, the flower-like hierarchical architectures assembled from aniline oligomers by a template-free method are reported. Their formation process is ascribed to the self-assembly of oligoanilines through non-covalent interactions, such as hydrogen bonding, hydrophobic forces, and π-π stacking. The model of directional growth is offered to explain the formation of petal-like objects and, subsequently, flowers. In order to investigate the chemical structure of the oligomers, a series of characterizations have been carried out, such as matrix-assisted laser desorption ionization, time-of-flight mass spectrometry, gas chromatography coupled with mass spectrometry analysis, X-ray diffraction, and UV/Vis, Fourier-transform infrared, and Raman spectroscopies. Based on the results of characterization methods, a formation mechanism for aniline oligomers and their self-assembly is proposed.