Elution Mechanism Research Articles

Investigating the different transformations of tetracycline using birnessite under different reaction conditions and various humic acids

Prior studies have successfully used manganese oxides to facilitate the transformation of tetracycline in aqueous solution. To further understand the kinetic and the transformation pathway of tetracycline via birnessite (δ-MnO2) under different conditions, experiments were conducted at pH levels of 3, 6, and 9 in the presence or absence of Aldrich humic acid (ADHA). Tetracycline removal followed the pseudo-second-order reaction model in all investigated cases, and the removal efficiency (g mg−1 h −1) followed the following trend: pH 3 (0.45/0.27) > pH 6 (0.036/0.087) > pH 9 (0.036/0.103) in the absence/presence of ADHA. Liquid chromatography–mass spectrometry/mass spectrometry results identified five main transformation products at m/z 495, 477, 493, 459, and 415, produced by the transformation reactions, including hydration, oxidation, desaturation, and oxy reduction. Notably, in the presence of ADHA at pH 3, products with higher toxicity secondary (m/z 477 and 495) were reduced, while less toxicity products (m/z 459 and 415) were enhanced. The experiments utilizing tetracycline and δ-MnO2 with varied humic acids (HA) revealed that HA with high polar organic carbon groups, such as O-alkyl, exhibited higher removal efficiency at pH 6. This research offers the first comprehensive insights into the pathway transformations of tetracycline via δ-MnO2 under different pH conditions and HA types. For further understanding, future work should investigate the binding of HA, TTC, and/or Mn2+ and the oxidation capacity of MnO2 after the reaction to clarify Mn2+ elution mechanisms.

Therapeutic efficacy of vancomycin-loaded carbon fiber-reinforced polyetheretherketone hip stem for periprosthetic joint infection: A pilot study.

A carbon fiber-reinforced polyetheretherketone (CFR/PEEK) hip stem with a special antibiotic elution mechanism is under development to treat periprosthetic joint infection (PJI). The antibiotic elution characteristics of intramedullary implants were experimentally investigated, and the efficacy of revision surgery using a therapeutic stem in treating ovine PJI was examined. To evaluate elution characteristics, the intramedullary vancomycin-loaded CFR/PEEK cylindrical implants were inserted in the distal femur of nine sheep, and the vancomycin elution rate was measured at 2, 7, and 21 days. To evaluate therapeutic efficacy, the PJI model with staphylococcus aureus was attempted to create for five sheep. Moreover, the therapeutic vancomycin-loaded CFR/PEEK stem was implanted during one-stage revision surgery. Three weeks after revision surgery, the treatment efficacy was evaluated based on bacterial cultures and wound findings. In addition, the vancomycin elution rate from the stem was measured. On average, the cylindrical implants eluted approximately 70% vancomycin in 21 days. Of the five sheep attempting to create a PJI model, three were successfully infected with S. aureus as intended for verification of treatment efficacy. In all three joints, negative bacterial cultures and no purulence were observed 3 weeks after revision surgery. The vancomycin elution rates from the stems were >70%. Efficient elution of vancomycin was confirmed by the experimental implant inserted into the bone marrow and the stem in actual PJI treatment. Using a novel therapeutic stem with an antibiotic elution mechanism in one-stage revision surgery, successful treatment was demonstrated in all S. aureus-induced PJIs.

Practical study on the impact of injection conditions in gradient elution mode for the analysis of therapeutic proteins when using very short columns

The impact of injected sample volume on apparent efficiency has been studied for very short columns in a systematic way. For large molecules such as therapeutic proteins, it was found that relatively large volumes can be injected onto ultra-short RPLC and IEX columns (i.e. L < 50 mm) without significantly affecting the quality of the separation. This favourable behavior is due to the on-off elution mechanism of large molecules and to the fact that therapeutic protein samples are formulated in aqueous-based media, which is the weakest solvent in RPLC and IEX. Therefore, their peak is strongly focused at the column inlet even when large volume is injected, and pre-column peak dispersion is compensated. However, ultra-short HILIC columns do not seem to be favorable, as they require for very low injection volume to avoid detrimental peak splitting and breakthrough effects. Such peak distortion is related to the inherent solvent mismatch between sample diluent (aqueous) and mobile phase strength (highly organic in HILIC). When studying mass load, the ranking of the elution modes was the same, and the largest relative mass could be injected onto IEX columns (as large as 10% sample to sorbent mass), without affecting the separation quality.

Assessing the impacts of fine sediment removal on endogenous pollution release and microbial community structure in the shallow lakes

Resuspension is a crucial process for releasing endogenous pollution from shallow lakes into the overlying water. Fine particle sediment, which has a higher contamination risk and longer residence time, is the primary target for controlling endogenous pollution. To this end, a study coupling aqueous biogeochemistry, electrochemistry, and DNA sequencing was conducted to investigate the remediation effect and microbial mechanism of sediment elution in shallow eutrophic water. The results indicated that sediment elution can effectively remove some fine particles in situ. Furthermore, sediment elution can inhibit the release of ammonium nitrogen and total dissolved phosphorous into the overlying water from sediment resuspension in the early stage, resulting in reductions of 41.44 %–50.45 % and 67.81 %–72.41 %, respectively. Additionally, sediment elution greatly decreased the concentration of nitrogen and phosphorus pollutants in pore water. The microbial community structure was also substantially altered, with an increase in the relative abundance of aerobic and facultative aerobic microorganisms. Redundancy analysis, PICRUSt function prediction, and the correlation analysis revealed that loss on ignition was the primary factor responsible for driving changes in microbial community structure and function in sediment. Overall, the findings provide novel insights into treating endogenous pollution in shallow eutrophication water.

3D printing of the multifunctional fixed-bed reactor and matched 3D-CeO2/ATP monolithic adsorbent for adsorption desulfurization

The construction of monolithic adsorbents can promote the potential industrial application for adsorption desulfurization of fuel. Herein, the 3D-CeO2/ATP monolithic adsorbents were successfully constructed through a 3D printing strategy, possessing superior adsorption desulfurization performance of more than 85 % sulfur removal under optimized adsorption reaction conditions at room temperature. Combined with the 3D-printed multifunctional fixed-bed reactor, the reaction process capable of adsorption-elution was designed for continuously realizing the deep adsorption of sulfide in fuel and the resource recovery of high-value sulfide products. The structure and physicochemical property of 3D-CeO2/ATP monolithic adsorbents were analyzed by series of characterizations, and the adsorption and elution mechanism were investigated in detail. The results reveal that the monolithic adsorbent with the internal staggered honeycomb structure was compared with that of the traditional in-line structure in terms of adsorption performance and computational fluid dynamics (CFD) fluid simulations, reflecting the advantages of 3D printing in structural forming to enhance mass transfer for promoting the adsorption process. Moreover, the 3D-printed monolithic adsorbents exhibit exceptional mechanical stability and good circulation performance, reaching the requirements for potential industrial application.

Study on the elution mechanism of HgO on mercury-loaded adsorbent in KCl solution via temperature programmed desorption (TPD) method

MnTi adsorbent prepared by precipitation method was used to remove elemental mercury in pure nitrogen atmosphere, and TPD method was employed to investigate the mechanism of mercury elution from mercury-loaded MnTi adsorbent in KCl solution. In the gas-phase mercury adsorption process, the MnTi adsorbent removed mercury with a high efficiency of 50% under pure nitrogen atmosphere. The effects of stirring time, eluent concentration, and pH on Hg elution efficiency were evaluated in the liquid-phase Hg elution process. Mercury elution was assisted by adequate stirring time and eluent concentration. The pH value of the environment influenced mercury elution, with an acidic environment being more effective for mercury oxide elution. According to the experimental results, the highest mercury elution efficiency of 0.5 M KCl solution was 79%. The active chlorine produced during the elution process was valuable for reuse. The mercury removal performance of the reused MnTi adsorbent was not significantly different from that of the fresh adsorbent. The elution mechanism of HgO was also proposed, with the key link being the reaction of HgO(red) in solution with excess Cl− to form [HgCl4]2− complexes, which then entered the liquid phase. It was possible to conclude that KCl solution had a high potential for mercury elution from mercury-carrying adsorbents and waste adsorbent reuse.

Laser Microperforation Assisted Drug-Elution from Biodegradable Films.

In a modern high-tech medicine, drug-eluting polymer coatings are actively used to solve a wide range of problems, including the prevention of post-surgery infection, inflammatory, restenosis, thrombosis and many other implant-associated complications. For major assumptions, the drug elution mechanism is considered mainly to be driven by the degradation of the polymer matrix. This process is very environmentally dependent, unpredictable and often leads to a non-linear drug release kinetic. In the present work, we demonstrate how the laser microperforation of cargo-loaded biodegradable films could be used as a tool to achieve zero-order release kinetics with different elution rates. The effects of the laser-induced hole’s diameter (10, 18, 22, 24 µm) and their density (0, 1, 2, 4 per sample) on release kinetic are studied. The linear dynamics of elution was measured for all perforation densities. Release rates were estimated to be 0.018 ± 0.01 µg/day, 0.211 ± 0.08 µg/day, 0.681 ± 0.1 µg/day and 1.19 ± 0.12 µg/day for groups with 0, 1, 2, 4 microperforations, respectively. The role of biodegradation of the polymer matrix is reduced only to the decomposition of the film over time with no major influence on elution rates.

Investigation of the Surface Elution Mechanism of Citric Acid-Coordinated Hydroxyapatite Nanoparticles in Biological Solutions

Investigation of the Surface Elution Mechanism of Citric Acid-Coordinated Hydroxyapatite Nanoparticles in Biological Solutions

Recovery of cobalt from spent lithium ion batteries utilizing surface modified graphene oxide

Metal content present in the spent lithium ion batteries (LIBs) make their recycling vital for resources conservation and environmental sustainability. Cobalt, grouped among critical, valuable and strategic metals, is the basic part of the LIBs cathode and defines its recycling economic capacity. In the present work, an attempt has been made to develop an efficient hydrometallurgical technique based on solid phase extraction method for the recovery of cobalt from leach solution of waste LIBs. An adsorbent was synthesized by diazotization of p-phenylenediamine modified graphene oxide (GO-PPDA) sheets with disodium 1-nitroso-2-naphthol-3-6-disulphonate (nitroso R-salt, NRS) in one pot process of Mill's reaction. Maximum retention of cobalt (99.9%) was achieved at pH 5.5–6.5. Adsorption kinetics favour complexation as a separation mechanism following second order kinetics model with R2 value of 0.9999 with sample flow rate of 1.5 mL/min. Langmuir isothermal model (R2 = 0.998) also confirm monolayer chemisorption mechanism with 29.7 mg/g adsorption capacity. The two-step elution mechanism enables us to achieve 99.5% extraction efficiency with ~98% purity. The chelating adsorbent was found reasonably stable even after the 30th cycle of adsorption and desorption with <2% decrease in removal efficiency. The results show that the proposed adsorbent is successful in terms of selectivity, reusability, analytical merit and stability.

Automated ion exchange chromatography screening combined with in silico multifactorial simulation for efficient method development and purification of biopharmaceutical targets.

Bioprocess development of increasingly challenging therapeutics and vaccines requires a commensurate level of analytical innovation to deliver critical assays across functional areas. Chromatography hyphenated to numerous choices of detection has undeniably been the preferred analytical tool in the pharmaceutical industry for decades to analyze and isolate targets (e.g., APIs, intermediates, and byproducts) from multicomponent mixtures. Among many techniques, ion exchange chromatography (IEX) is widely used for the analysis and purification of biopharmaceuticals due to its unique selectivity that delivers distinctive chromatographic profiles compared to other separation modes (e.g., RPLC, HILIC, and SFC) without denaturing protein targets upon isolation process. However, IEX method development is still considered one of the most challenging and laborious approaches due to the many variables involved such as elution mechanism (via salt, pH, or salt-mediated-pH gradients), stationary phase's properties (positively or negatively charged; strong or weak ion exchanger), buffer type and ionic strength as well as pH choices. Herein, we introduce a new framework consisting of a multicolumn IEX screening in conjunction with computer-assisted simulation for efficient method development and purification of biopharmaceuticals. The screening component integrates a total of 12 different columns and 24 mobile phases that are sequentially operated in a straightforward automated fashion for both cation and anion exchange modes (CEX and AEX, respectively). Optimal and robust operating conditions are achieved via computer-assisted simulation using readily available software (ACD Laboratories/LC Simulator), showcasing differences between experimental and simulated retention times of less than 0.5%. In addition, automated fraction collection is also incorporated into this framework, illustrating the practicality and ease of use in the context of separation, analysis, and purification of nucleotides, peptides, and proteins. Finally, we provide examples of the use of this IEX screening as a framework to identify efficient first dimension (1D) conditions that are combined with MS-friendly RPLC conditions in the second dimension (2D) for two-dimensional liquid chromatography experiments enabling purity analysis and identification of pharmaceutical targets.

Dynamic elution of residual ammonium leaching agent from weathered crust elution-deposited rare earth tailings by magnesium chloride

The release of residual ammonium (RA) leaching agent from weathered crust elution-deposited rare earth tailings would cause serious environmental pollution, and it was necessary to efficiently remove it from the ore body before the mine closure. In this study, occurrence states of the RA were determined and dynamic elution of RA from rare earth tailings by using magnesium chloride as eluent was investigated. Effects of initial concentration, pH, flow rate, and particle size on the ammonium removal efficiency were investigated, and variations of ammonium occurrence states before and after elution were determined. Lastly, elution mechanism was discussed. Results showed that removal efficiency of RA by magnesium chloride was significantly higher than that by deionized water, and elution efficiency of RA could reach about 95.7% at the optimum laboratory experiment conditions. Energy dispersive spectrometer (EDS) analysis illustrated that the residual ammonium was replaced by Mg2+ during the elution process, and occurrence state experimental results showed that 94.0% of water-soluble and adsorbable ammonium was eluted. The empirical kinetic equation of eluting RA by magnesium chloride was established as 1–2/3α-(1-α)2/3= 0.02*C00.6t. This study provided a valuable method for reducing environmental pollution caused by the release of the residual ammonium from the rare earth tailings.

Highly Efficient Uptake of Cs+ by Robust Layered Metal-Organic Frameworks with a Distinctive Ion Exchange Mechanism.

137Cs with strong radioactivity and a long half-life is highly hazardous to human health and the environment. The efficient removal of 137Cs from complex solutions is still challenging because of its high solubility and easy mobility and the influence of interfering ions. It is highly desirable to develop effective scavengers for radiocesium remediation. Here, the highly efficient uptake of Cs+ has been realized by two robust layered metal–organic frameworks (MOFs), namely [(CH3)2NH2]In(L)2·DMF·H2O (DMF = N,N′-dimethylformamide, H2L= H2aip (5-aminoisophthalic acid) for 1 and H2hip (5-hydroxyisophthalic acid) for 2). Remarkably, 1 and 2 hold excellent acid and alkali resistance and radiation stabilities. They exhibit fast kinetics, high capacities (qmCs = 270.86 and 297.67 mg/g for 1 and 2, respectively), excellent selectivity for Cs+ uptake, and facile elution for the regeneration of materials. Particularly, 1 and 2 can achieve efficient Cs+/Sr2+ separation in a wide range of Sr/Cs molar ratios. For example, the separation factor (SFCs/Sr) is up to ∼320 for 1. Moreover, the Cs+ uptake and elution mechanisms have been directly elucidated at the molecular level by an unprecedented single-crystal to single-crystal (SC-SC) structural transformation, which is attributed to the strong interactions between COO– functional groups and Cs+ ions, easily exchangeable [(CH3)2NH2]+, and flexible and robust anionic layer frameworks with open windows as “pockets”. This work highlights layered MOFs for the highly efficient uptake of Cs+ ions in the field of radionuclide remediation.

干潟に散布した石炭灰造粒物からのミネラルの溶出機構

波･流れにより砂泥が活動するテラス護岸に散布された石炭灰造粒物（GCA）を対象に3種の溶出実験を行ない，GCAを構成するCSH，CaSO4等のセメント水和物の構造を推定した．溶出実験では塩水，純水，NP（NH4+，PO43-）溶液でのGCAからのイオンの溶出傾向を分析して，GCAの溶解特性からセメント水和物の組成を検討した．この結果，Na+やPO43-の吸脱着がCa2+，SiO2，OH-の溶出量に寄与すること，干潟に202日と609日間散布されたGCAからもCa2+，SiO2，OH-の溶出が継続することを明らかにした．これらの成果から，GCAを構成するCSHはSiリッチなC/N比が不均一の低Ca型であること，低Ca型CSHからは持続的なSiとOH-の溶出が期待できること，SiO2離脱面にNa+やPO43-が吸着しGCAの溶解を促進すること等を明らかにした．

Lactate released from human fibroblasts enhances Ni elution from Ni plate

Elution of Ni ions from medical devices induces inflammation and toxicity. We previously reported that elution of Ni ions from Ni wires induced COX-2 expression and increased lactate production, but whether lactate is involved in the further elution of Ni ions remains unclear. In this study, using KMST-6, a human fibroblast cell line, we examined the molecular mechanisms by which Ni ions increase lactate release and the role of lactate in enhancing the elution of Ni ions. When KMST-6 cells were incubated on a Ni plate or stimulated with NiCl2 (1 mM), the expression of glucose transporter 1 (GLUT1), hexokinase 2 (HK2), and lactate dehydrogenase A (LDHA), and the release of lactate were enhanced. The NiCl2 (1 mM)-induced expression of these genes was inhibited by a hypoxia-inducible factor-1α (HIF-1α) inhibitor, PX-478 (10–25 μM). Stimulation of cells with a prolyl hydroxylase domain (PHD) inhibitor, roxadustat, increased the expression of these genes, lactate release, and elution of Ni ions at 10 μM. A monocarboxylate transporter-4 (MCT4) inhibitor, syrosingopine, inhibited lactate release from roxadustat-treated cells and reduced the elution of Ni ions by the cells at 10 μM. Finally, syrosingopine (10 μM) reduced the elution of Ni ions by the cells from the Ni plate. These results suggest that elution of Ni ions from metals promotes the production of lactate via HIF-1α-mediated gene expression and causes further Ni elution. Thus, Ni ions show a positive feedback mechanism of Ni elution, and this step may be potentially targeted to protect against metal elution from metal devices.

Use of Ultrashort Columns for Therapeutic Protein Separations. Part 1: Theoretical Considerations and Proof of Concept.

Due to the particular elution mechanism observed with large solutes (e.g., proteins) in liquid chromatography, column length has less impact in controlling their retention compared to small solutes. Moreover, long columns-in theory-just broaden the peaks of large solutes since a great part of the column only acts as void (extra) volume. Such a theory suggests that using very short columns should result in comparable separation quality versus using long columns and make it possible to perform faster (high-throughput) analyses. Therefore, the elution behavior of various therapeutic monoclonal antibodies and their fragments (25-150 kDa) has been investigated using modern instrumentation and column formats. The possibilities offered by narrow-bore columns packed with state-of-the-art 2.7 μm superficially porous particles with 5, 50, 100, and 150 mm lengths have been compared. In particular, the impact of gradient steepness and column length on separation efficiency was evaluated. Using 5 mm × 2.1 mm columns, it has become possible to separate antibody fragments and antibody-drug conjugate species in less than 30 s. Such fast methods can be very useful for high-throughput screening purposes in biopharmaceutical industries.

Investigation of the Presence and Possible Migration from Microplastics of Phthalic Acid Esters and Polycyclic Aromatic Hydrocarbons

The work detailed here examined the presence and possibility of leaching of phthalic acid esters (PAEs) and polycyclic aromatic hydrocarbons (PAHs) from various products in everyday use. Due to the complicated matrix, which is plastic, extraction parameters should be selected separately each time. The properties of both the extractant and the material selected for testing should also be taken into account, which is very difficult in practice. In addition, when designing new methods, it is particularly important to take into account the principles of green chemistry so as not to burden the environment additionally. For this purpose, it is important to know the factors that affect the extraction of impurities. Therefore, the main objective was to assess the impact of selected environmental conditions on the process by which such pollutants in plastics like polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP) and rubber migrate. Analysis inter alia addressed the impacts of type of plastic, migration time, temperature and microplastic particle size. It proved possible to note the presence in PVC and rubber of both PAEs and PAHs—as substances posing a particular threat to the environment. One of the former is the commonly-used plasticiser di(2-ethylhexyl) phthalate (DEHP), a listed priority hazardous substance under the provisions of Directive 2013/39/EU as regards priority substances in the field of water policy. As monitoring of this substance in the environment indicates amounts that are increasing steadily, the design of effective removal methods needs to start with initial estimates of amounts appearing in the environment over time. Main sources need to be explored, albeit in the certain knowledge that the ubiquitous microplastics are among these, inter alia as influenced by elution mechanisms. An attempt was also made to identify and characterise other auxiliary substances added to plastics as they are being produced. Indeed, chromatograms and GC/MS spectra suggest leaching of many other plastic substances. Relationships between eluted pollutants were also sought.

New Insights into the Chromatography Mechanisms of Ion-Exchange Charge Variant Analysis: Dispelling Myths and Providing Guidance for Robust Method Optimization.

Charge variant analysis is a widely used analytical tool in characterization of monoclonal antibodies (mAbs). It depicts the heterogeneity of charge variant forms, some of which may differ by only minor modifications of a single amino acid. The analysis ensures product consistency with no unwanted changes to the protein. With increasing numbers of new mAb drug products emerging in the market, the need for a robust charge variant analysis has intensified. The charge variant profiles often display partially resolved peaks on shoulders of larger peaks. This puts considerably more pressure on the robustness of the method to maintain the suboptimum selectivity. New products and techniques have emerged to address these requirements, in addition to the pre-existing older methods that may not have been optimized correctly in the past. This has led to some confusion as to the best approach and strategies in optimization of charge variant analysis. We show studies from several different approaches using on-line pH monitoring to check the performance characteristics of the methods. This has led to new insights on the interactions between the protein, column, and buffer constituents. We dispel some inaccurate assumptions about the different ion-exchange elution mechanisms and suggest ways to develop high-throughput methods that remain robust and of high resolution. Streamlined automatable method development tools are presented that will result in more efficient method optimization. The mechanisms behind poor chromatography design have provided an alternative explanation behind some methods failing when in the QC laboratories.

Tuning Crystal Structures of Iron-Based Metal-Organic Frameworks for Drug Delivery Applications.

Iron-based metal–organic frameworks (Fe-MOFs) have emerged as promising candidates for drug delivery applications due to their low toxicity, structural flexibility, and safe biodegradation in a physiological environment. Here, we studied two types of Fe-MOFs: MIL-53 and MIL-88B, for in vitro drug loading and releasing of ibuprofen as a model drug. Both Fe-MOFs are based on the same iron clusters and organic ligands but form different crystal structures as a result of two different nucleation pathways. The MIL-53 structure demonstrates one-dimensional channels, while MIL-88B exhibits a three-dimensional cage structure. Our studies show that MIL-53 adsorbs more ibuprofen (37.0 wt %) compared to MIL-88B (19.5 wt %). A controlled drug release was observed in both materials with a slower elution pattern in the case of the ibuprofen-encapsulated MIL-88B. This indicates that a complex cage structure of MIL-88 is beneficial to control the rate of drug release. A linear correlation was found between cumulative drug release and the degree of material degradation, suggesting the biodegradation of Fe-MILs as the main drug elution mechanism. The cytotoxicity of MIL-88B was evaluated in vitro with NIH-3T3 Swiss mouse fibroblasts, and it shows that MIL-88B has no adverse effects on cell viability up to 0.1 mg/mL. This low toxicity was attributed to the morphology of MIL-88B nanocrystals. The very low toxicity and controlled drug release behavior of Fe-MIL-88B suggest that better materials for drug-delivery applications can be created by controlling not only the composition but also the crystal structure and nanoparticle morphology of the material.

Mechanism of silicate elution by hydrogen sulfide from bottom sediment in a brackish lake

Highly concentrated dissolved silicate was detected in pore water from anoxic-reducing sediment in Lake Nakaumi, a brackish lake. Silicate concentration also simultaneously increased with total hydrogen sulfide concentration during the summer. Generally, dissolved silicate is readily adsorbed onto ferric hydroxide and precipitates in an oxidative environment. In this study, we focused on the behavior of ferric hydroxide adsorbing silicate in sediment and determined that hydrogen sulfide was the main cause of dissolved silicate elution from ferric hydroxide adsorbing silicate because the hydrogen sulfide produced via microbiological processes in the anoxic-reducing environment was reducible for other metal oxides. According to laboratory experiments, silicate was released from ferric hydroxide by reacting with sodium sulfide, causing increasing elution of dissolved silicate from anoxic-reducing sediments with increasing concentration of sodium sulfide in the solutions. This result shows that hydrogen sulfide is very crucial for silicate release under a reducing environment. Therefore, in Lake Nakaumi, silicate would be released from the bottom after ferric hydroxide adsorbing silicate reacted with hydrogen sulfide in a summer reductive environment.

Kinetics of Elution of Gentamicin from a Gentamicin-Loaded PMMA Bone Cement

Antibiotic-loaded poly (methyl methacrylate) bone cement (ALBC) is widely used for anchoring joint replacements as a means of reducing the potential for peri-prosthetic joint infection (primary cases) and treating a patient who has an infected joint replacement (revision cases). One shortcoming of the cement is the high maximum exothermic temperature experienced upon polymerization (Tmax), a phenomenon that, it has been postulated, may cause or be implicated in thermal necrosis of peri-prosthetic tissues. There are many reports in the literature on methods of reducing Tmax, with one such study involving the addition of a phase change material (microencapsulated paraffin) (MEPAR) to the cement powder or adding a chain-stopping chemical (1-dodecyl mercaptan) (DDM) to the liquid. In that report, the results of gentamicin elution tests were presented. In the present work, those results were used to calculate various indices of gentamicin elution kinetics, namely 1) diffusion coefficient (Dgent); and 2) values of the coefficients in four equations that are widely used to model antibiotic elution from ALBCs. We found 1) the difference in Dgent of either a MEPAR- or DDM-containing formulation, on the one hand, and that of the control cement, on the other, was not significant; and 2) a consistent trend in the value of only one coefficient in one of the four model equations, with this change suggesting insignificant difference in gentamicin elution mechanism between an experimental cement formulation and the control cement. The implications of these findings for guiding selection of additives that simultaneously produce significant reduction of Tmax but minimal effect on gentamicin elution kinetics are discussed. This guide is a novel contribution to the literature.