Fatma Ibis

A droplet-based microfluidic platform is presented to study the nucleation kinetics of calcium oxalate monohydrate (COM), the most common constituent of kidney stones, while carefully monitoring the pseudo-polymorphic transitions. The precipitation kinetics of COM is studied as a function of supersaturation and pH as well as in the presence of inhibitors of stone formation, magnesium ions (Mg²⁺), and osteopontin (OPN). We rationalize the trends observed in the measured nucleation rates leveraging a solution chemistry model validated using isothermal solubility measurements. In equimolar calcium and oxalate ion concentrations with different buffer solutions, dramatically slower kinetics is observed at pH 6.0 compared to pHs 3.6 and 8.6. The addition of both Mg²⁺ and OPN to the solution slows down kinetics appreciably. Interestingly, complete nucleation inhibition is observed at significantly lower OPN, namely, 3.2 × 10⁻⁸ M, than Mg²⁺ concentrations, 0.875 × 10⁻⁴ M. The observed inhibition effect of OPN emphasizes the often-overlooked role of macromolecules on COM nucleation due to their low concentration presence in urine. Moreover, analysis of growth rates calculated from observed lag times suggests that inhibition in the presence of Mg²⁺ cannot be explained solely on altered supersaturation. The presented study highlights the potential of microfluidics in overcoming a major challenge in nephrolithiasis research, the overwhelming physiochemical complexity of urine.

Accurate Calcium Oxalate Monohydrate (COM) solubility measurements are essential for elucidating the physiochemical mechanism behind the formation of kidney stones, nephrolithiasis. Yet the reported solubility values of COM in ultrapure water, arguably the simplest solvent relevant for nephrolithiasis, vary significantly depending on implemented method. To address this variation, we present an experimental study of the solubility of COM validated by a model based on the Debye–Hückel theory describing the solution chemistry and the complex formation. We also carefully monitor potential pseudopolymorphic/hydrate transitions during the solubility measurements with in-situ and ex-situ methods. Our results indicate that the solubility of COM in ultrapure water is a weak function of temperature. However, the measured solubility varies significantly in buffer solutions across physiologically relevant pH values at body temperature. The proposed model explains observed trends as a combined effect of ionic strength, protonation reactions, and soluble complex formation. Moreover, it predicts solubility of COM in buffer solutions remarkably well using our measurements in ultrapure water as input, demonstrating the consistency of presented approach. The presented study parleying experiments and modelling provides a solid stepping stone to extend the physiochemical understanding of nephrolithiasis to more realistic solutions laden with biological complexity.

Surgical site infections have a remarkable impact on morbidity, extended hospitalization and mortality. Sutures strongly contribute to development of surgical site infections as they are considered foreign material in the human body. Sutures serve as excellent surfaces for microbial adherence and subsequent colonization, biofilm formation and infection on the site of a surgery. Various antimicrobial sutures have been developed to prevent suture-mediated surgical site infection. However, depending on the site of surgery, antimicrobial sutures may remain ineffective, and antimicrobial agents on them might have drawbacks. Plasma, defined as the fourth state of matter, composed of ionized gas, reactive oxygen and nitrogen species, free radical and neutrals, draws attention for the control and prevention of hospital-acquired infections due to its excellent antimicrobial activities. In the present study, the efficacy of non-thermal atmospheric plasma treatment for prevention of surgical site infections was investigated. First, contaminated poly (glycolic-co-lactic acid), polyglycolic acid, polydioxanone and poly (glycolic acid-co-caprolactone) sutures were treated with non-thermal atmospheric plasma to eradicate contaminating bacteria like Staphylococcus aureus and Escherichia coli. Moreover, sutures were pre-treated with non-thermal atmospheric plasma and then exposed to S. aureus and E. coli. Our results revealed that non-thermal atmospheric plasma treatment effectively eradicates contaminating bacteria on sutures, and non-thermal atmospheric plasma pre-treatment effectively prevents bacterial colonization on sutures without altering their mechanical properties. Chemical characterization of sutures was performed with FT-IR and XPS and results showed that non-thermal atmospheric plasma treatment substantially increased the hydrophilicity of sutures which might be the primary mechanism for the prevention of bacterial colonization. In conclusion, plasma-treated sutures could be considered as novel alternative materials for the control and prevention of surgical site infections.

Öz Diş eksikliklerinin tedavisinde dental implant uygulamaları günümüzde sıklıkla tercih edilmektedir. Ancak dental implantların kemik ile entegrasyonu (osseointegrasyon) için beklenmesi gereken sürenin uzun olması bu tedavi yönteminin en önemli dezavantajı olarak karşımıza çıkmaktadır. Literatürde, osseointegrasyon için beklenen sürenin kısaltılması amacıyla yapılmış çok sayıda çalışma karşımıza çıkmaktadır. Osseointegrasyon süresinin kısaltılması amacıyla yüzey hidrofilitesini arttırarak hücre tutunma oranını yükselten Atmosferik Soğuk Plazma (ASP) uygulaması titanyum implantlar için uygulanmakta ve olumlu sonuçlar alındığı iddia edilmektedir. Bu çalışmada yüzey temas açısını düşürmek ve osteoblast hücrelerin yüzeye tutulumunu artırmak için titanyum disklerin yüzeyine ASP uygulandı. Farklı zaman aralıklarında uygulanan ASP öncesinde ve sonrasında temas açısı ölçümleri yapıldı. ASP uygulamasının osteoblast hücre hareketi üzerine etkileri immünohistokimyasal ve SEM analizi ile değerlendirildi. Uygulama sonrasında temas açısı değerlerinde anlamlı bir şekilde düşüş meydana geldi. Atmosferik soğuk plazma uygulaması osteblast hücreler üzerinde oksidatif stres meydana getirmeden disk yüzeyinde çoğlamasıını ve tutulumunu artırdı.

Objectives. Antimicrobial activities of non-thermal atmospheric plasma-treated liquids on various bacterial and fungal strains in their planktonic and biofilm forms have been widely reported. Since most of the plasma-treated liquids are water based, they might be washed off certain surfaces and they cannot be applied for the infections of respiratory tract. In the present study we have tested antimicrobial activities of plasma-treated N-acetyl cysteine solution (NAC), phosphate buffered saline (PBS) solution and deionized water when nebulized over planktonic forms of E. coli and S. aureus.Methods. Antimicrobial activities of nebulized plasma-treated liquids were evaluated with zone of inhibition test and colony counting assay. Moreover pH of NAC, PBS solution and deionized water were measured before, after plasma treatment and during nebulization since low pH is well known consequence observed in plasma-treated liquids. Results. Our results have revealed that pH of plasma-treated NAC, PBS solution and DIW decreases after plasma treatment consistent with previous reports and does not change during nebulization. Moreover, antimicrobial activity assessment indicates that nebulized plasma-treated NAC shows the strongest antimicrobial activity, which leads complete inactivation of bacteria for 103 to 106 CFU/ml initial bacterial load and 5-log reduction for 107 CFU/ml initial bacterial load on both E. coli and S. aureus.Conclusions. Plasma-treated liquids could retain their antimicrobial activity during nebulization and nebulization could be considered as a future alternative method for delivery of plasma-treated liquids for respiratory tract infections.