Crystal Inhibition Research Articles

Effect of Polyvinylpyrrolidone Content on Pure Titanium Injection Molding

In water-soluble binder systems, polyethylene glycol (PEG) and polymethylmethacrylate (PMMA) are often used as primary and secondary components. The PEG/PMMA binder system is clean and environmentally friendly, but the discrepancy between the crystallization temperature of PEG and the glass transition temperature of PMMA leads to the generation of pores in the feedstock. The solidification pores have an adverse impact on the final mechanical properties of the samples. Polyvinylpyrrolidone (PVP), as a crystallization inhibitor, can inhibit the formation of porosity. In this study, spherical titanium powder with a diameter of less than 45 μm was used as metal powder; the binder system consisted of PEG, PMMA and SA. Different increments of PVP (0, 10%, 20%, 30 wt.%) were added to the PEG/PMMA binder system. The uniformity of the feedstock and the open channels generated after debinding were observed using SEM. The pores’ condition before and after debinding was studied using Micro CT, and the mechanical properties of the samples were also detected. By comparing the macroscopic and microscopic morphologies of the injected samples and mechanical properties of the sintered samples, it was found that a PVP content of 20 wt.% resulted in the best properties.

Comparative Evaluation of Particle Size Reduction, Salt Formation, and Amorphous Formulation on the Biopharmaceutical Performance of a Weak Base Drug Candidate.

Various approaches have been developed to enhance the solubility or dissolution rate for the delivery of poorly water-soluble molecules. In this work, guided by an in silico solubility sensitivity analysis for oral absorption, a comparative assessment of the biopharmaceutical performance of a jet-milled free base, a tosylate salt, and a 50:50 (w/w) amorphous solid dispersion (ASD) with hydroxypropyl methylcellulose acetate succinate (HPMCAS) of a weak base drug candidate, GDC-3280, was conducted. Successful particle size reduction without amorphization or form change was confirmed for the jet-milled free base. The potential of solubility enhancement and desupersaturation risk were identified for tosylate salt and ASD formulation by measurements of tosylate salt solubility product constant (Ksp) and amorphous solubility of GDC-3280. In vitro dissolution testing demonstrated dissolution rate improvement for the jet-milled free base when compared with the unmilled free base and confirmed solubility enhancement followed by desupersaturation for GDC-3280 tosylate salt and ASD formulation. A crystallization inhibitor, hydroxypropyl methylcellulose (HPMC), was found to slow down the desupersaturation of tosylate salt solution, providing general insights for the development of pharmaceutical salts with disproportionation risks. Finally, a pharmacokinetic study in dogs showed that the in vivo exposure increased by 1.7- to 2-fold for the tosylate salt and ASD formulation compared with the jet-milled free base, consistent with the in silico solubility sensitivity analysis for the fraction of drug absorbed. Overall, this work provides insights into the evaluation of multiple formulation approaches for enhancing the biopharmaceutical performance of poorly water-soluble drugs.

Effect of seed on synthesis of binder‐free mordenite for dimethyl ether carbonylation

AbstractA series of binder‐free mordenite (MOR) zeolites were successfully prepared by hydrothermal conversion of shaped precursors containing aluminosilicate and MOR seeds. In the synthesis of seed crystals, hexadecyltrimethylammonium bromide (CTAB) was used as a crystal growth inhibitor as well as a pore filler to adjust the morphology and introduce mesoporous pores. As a result, large aggregates, assembled nanosheets, and flowers‐like MOR were successfully synthesized with these MOR seeds. The effect of seed morphology on the performance of the binder‐free MOR was studied by scanning electron microscopy (SEM), N2 adsorption–desorption, and NH3‐TPD characterization techniques. It was found that the mesopore volume of formed MOR was positively correlated with those of the seeds. The synthesized binder‐free MOR showed high activity (0.28 g methyl acetate gcat−1 h−1), 100% selectivity, and high stability in dimethyl ether (DME) carbonylation to methyl acetate, which can be attributed to the larger surface area and more mesopores. The synthesis of MOR nano‐assemblies via this cost‐effective strategy has a wide range of potential applications.

L-lysine-assisted synthesis of gismondine and chabazite nanozeolites for direct air capture of CO2

The search for more efficient and selective solid adsorbents towards carbon capture, particularly in trace CO2 concentration, remains a significant challenge. Here, we present the synthesis of nanocrystalline sodium gismondine (Na-GIS) with Si/Al = 2.5 and potassium chabazite (K-CHA) zeolites with Si/Al = 2.0 using L-lysine as a crystal growth inhibitor. Na-GIS nanozeolites were found to show a CO2 uptake as high as 0.70 mmol g−1 under direct air capture (DAC) conditions (i.e., 298 K and 400 ppm CO2), about 18 times greater than that of microcrystalline Na-GIS, together with high adsorbent stability. Such behavior was also observed for Na-CHA nanozeolites, although the extent of increase (0.47 vs 0.13 mmol g−1) was smaller compared to the microcrystalline counterpart. This study demonstrates that the introduction of nanocrystallinity into small-pore zeolites without losing intrinsic microporosity is a viable route to the development of more efficient zeolite-based DAC adsorbents.

Chemical Modification of Tiopronin for Dual Management of Cystinuria and Associated Bacterial Infections.

Cystinuria is an inherited autosomal recessive disease of the kidneys of recurring nature that contributes to frequent urinary tract infections due to bacterial growth and biofilm formation surrounding the stone microenvironment. In the past, commonly used strategies for managing cystinuria involved the use of (a) cystine crystal growth inhibitors such as l-cystine dimethyl ester and lipoic acid, and (b) thiol-based small molecules such as N-(2-mercaptopropionyl) glycine, commonly known as tiopronin, that reduce the formation of cystine crystals by reacting with excess cystine and generating more soluble disulfide compounds. However, there is a dearth of simplistic chemical approaches that have focused on the dual treatment of cystinuria and the associated microbial infections. This work strategically exploited a single chemical approach to develop a nitric oxide (NO)-releasing therapeutic compound, S-nitroso-2-mercaptopropionyl glycine (tiopronin-NO), for the dual management of cystine stone formation and the related bacterial infections. The results successfully demonstrated that (a) the antibacterial activity of NO rendered tiopronin-NO effective against the stone microenvironment inhabitants, Escherichia coli and Pseudomonas aeruginosa, and (b) tiopronin-NO retained the ability to undergo disulfide exchange with cystine while being reported to be safe against canine kidney and mouse fibroblast cells. Thus, the synthesis of such a facile molecule aimed at the dual management of cystinuria and related infections is unprecedented in the literature.

Effect of Structurally Related Compounds on Desupersaturation Kinetics of Indomethacin.

The pharmaceutical literature contains examples wherein desupersaturation from high concentrations does not proceed to equilibrium concentration of the thermodynamically most stable form but remains above equilibrium. The purpose of the current research was to investigate the effect of structurally related compounds on desupersaturation kinetics as a possible explanation for a higher than equilibrium solubility after crystal growth of γ-indomethacin (γ-IMC). Three structurally related compounds (SRC) - cis-sulindac (c-SUL), trans-sulindac (t-SUL) and indomethacin-related compound-A (IMC-A) -were investigated. Desupersaturation kinetics to the most stable γ-IMC, in the presence of c-SUL, t-SUL or IMC-A, was measured at pH 2.0. The SRCs c-SUL and t-SUL were effective crystallization inhibitors of IMC, while IMC-A was not a potent crystallization inhibitor of IMC. Among the sulindac isomers, t-SUL was a stronger crystallization inhibitor. The apparent solubility of γ-IMC crystals grown from supersaturated solutions in the presence of SRCs matched the equilibrium solubility of γ-IMC. During crystallization of IMC in the presence of IMC-A, the concentration of IMC-A declined initially but rebounded as supersaturation and crystallization rate of IMC declined, suggesting that IMC-A itself became incorporated in the IMC crystal lattice at higher degrees of IMC supersaturation. The results suggest that high apparent solubility after crystallization of IMC reported by several authors is not related to the presence of IMC-A impurity. The greater IMC crystal growth rate inhibition by t-SUL than by c-SUL was consistent with the proposed orientation of SUL molecules adsorbed on the IMC crystal, providing a mechanistic understanding of the inhibition.

Effects of Additives on the Physical Stability and Dissolution of Polymeric Amorphous Solid Dispersions: a Review.

Polymeric amorphous solid dispersion (ASD) is a popular approach for enhancing the solubility of poorly water-soluble drugs. However, achieving both physical stability and dissolution performance in an ASD prepared with a single polymer can be challenging. Therefore, a secondary excipient can be added. In this paper, we review three classes of additives that can be added internally to ASDs: (i) a second polymer, to form a ternary drug-polymer-polymer ASD, (ii) counterions, to facilitate in situ salt formation, and (iii) surfactants. In an ASD prepared with a combination of polymers, each polymer exerts a unique function, such as a stabilizer in the solid state and a crystallization inhibitor during dissolution. In situ salt formation in ASD usually leads to substantial increases inthe glass transition temperature, contributing to improved physical stability. Surfactants can enhance the wettability of ASD particles, thereby promoting rapid drug release. However, their potential adverse effects on physical stability and dissolution, resulting from enhanced molecular mobility and competitive molecular interaction with the polymer, respectively, warrant careful consideration. Finally, we discuss the impact of magnesium stearate and inorganic salts, excipients added externally upon downstream processing, on the solid-state stability as well as the dissolution of ASD tablets.

New insights into the nucleation of portlandite and the effects of polymeric additives

The crystallization of calcium hydroxide (Ca(OH)2, CH, portlandite) is a key process during the early stages of cement hydration. In the present work, we have revisited the formation of this mineral through nucleation and growth from supersaturated aqueous solutions, in the light of the currently emerging picture of multistage “non-classical” crystallization. To that end, we developed a titration-based assay, in which stock solutions of both relevant ions are added simultaneously into a reservoir, where supersaturation increases slowly at constant stoichiometry until nucleation occurs. This procedure allows both pre- and early post-nucleation phenomena to be analyzed quantitatively. Complementarily, the early stages of portlandite mineralization were probed by various advanced characterization techniques, including cryo-transmission electron microscopy (cryo-TEM), in-situ small-angle X-ray scattering (SAXS), pair distribution function (PDF) analysis of high-energy X-ray scattering (HEXS) data, and analytical ultracentrifugation (AUC). The experimental data show that the formation of calcium hydroxide starts with the association of ions into complexes and clusters, which subsequently coalesce to form amorphous nanoparticles – much like what has been observed in the case of calcium carbonate and other prominent minerals. Subsequently, these particles aggregate and build networks, which eventually transform into hexagonal Ca(OH)2 crystals. The presence of a soluble polycarboxylate – as a known inhibitor of portlandite crystallization – does not change the main characteristics of this multistep nucleation pathway, but it proved capable of significantly extending the lifetime of the amorphous intermediate phase and thus delaying the transition to the final crystalline phase. Our observations confirm the notion that “non-classical” crystallization is a much more common phenomenon than initially believed – and that, for minerals forming in aqueous environments, it may actually be the rule rather than the exception.

Effect of Phytate (InsP6) and Other Inositol-Phosphates (InsP5, InsP4, InsP3, InsP2) on Crystallization of Calcium Oxalate, Brushite, and Hydroxyapatite.

Pathological calcifications may consist of calcium oxalate (CaOx), hydroxyapatite (HAP), and brushite (BRU). The objective of this study was to evaluate the effect of phytate (inositol hexakisphosphate, InsP6), InsP6 hydrolysates, and individual lower InsPs (InsP5, InsP4, InsP3, and InsP2) on the crystallization of CaOx, HAP and BRU in artificial urine. All of the lower InsPs seem to inhibit the crystallization of calcium salts in biological fluids, although our in vitro results showed that InsP6 and InsP5 were stronger inhibitors of CaOx crystallization, and InsP5 and InsP4 were stronger inhibitors of BRU crystallization. For the specific in vitro experimental conditions we examined, the InsPs had very weak effects on HAP crystallization, although it is likely that a different mechanism is responsible for HAP crystallization in vivo. For example, calciprotein particles seem to have an important role in the formation of cardiovascular calcifications in vivo. The experimental conditions that we examined partially reproduced the in vivo conditions of CaOx and BRU crystallization, but not the in vivo conditions of HAP crystallization.

Efficacy of Theobromine and Its Metabolites in Reducing the Risk of Uric Acid Lithiasis

Uric acid lithiasis accounts for about 10% of all types of renal lithiasis. The most common causes of uric acid lithiasis are low urinary pH, followed by high concentration of urinary uric acid, and low diuresis. Treatment of patients consists of alkalinization of urine, reducing the consumption of purine-rich foods, and administration of xanthine oxidase inhibitors, because there are no established therapeutic inhibitors of uric acid crystallization. We recently found that theobromine inhibited uric acid crystallization in vitro, and that the increased urinary level of theobromine following its oral consumption was associated with the prevention of uric acid crystallization. In this study, we evaluated the inhibitory effects of theobromine metabolites and other methylxanthine-related compounds on uric acid crystallization. We also measured the urinary concentrations of theobromine and its metabolites in samples from healthy individuals and patients with uric acid stones and compared the extent of uric acid supersaturation and uric acid crystal formation in these different samples. Theobromine and other methylxanthines that lacked a substituent at position 1 inhibited uric acid crystallization, but other methylxanthines did not have this effect. Individuals with clinical parameters that favored uric acid crystallization did not develop uric acid crystals when theobromine and its metabolites were in the urine at high levels. Thus, theobromine and its metabolites reduced the risk of uric acid lithiasis.

Bifunctional catalysts based on hierarchical SAPO-41 nanosheet for Highly-efficient hydroisomerization of n-Hexadecane

Conversion of long-carbon chain n-alkanes into iso-alkanes is a key technology to improve the low-temperature fluidity of petroleum-based diesel and lubricating oil, as well as produce second-generation biodiesel from vegetable oils. Developing a highly efficient bifunctional catalysts is the key to realize this process. In this work, a series of hierarchical silicoaluminophosphate molecular sieves SAPO-41 nanosheet (S41-xBCl) were synthesized by using various amounts of 1-butyl-3-methylimidazolium chloride ionic liquid (BMIMCl) as a crystal growth inhibitor. The bifunctional catalysts Pd/S41-xBCl with merely 0.1 wt% Pd loading on the S41-xBCl samples were prepared by wetness impregnation, and the catalytic performance for hydroisomerization of n-hexadecane was tested. The catalytic performance of Pd/S41-xBCl markedly improved because of the enhanced diffusion properties of reactants and iso-alkene intermediates, as well as the realizing synergistic catalysis of metal and acid sites. The yield of iso-hexadecane over the catalyst Pd/S41-2BCl were as high as 83.4% at n-hexadecane conversion of 94.6%. This efficient catalyst with lower noble metal loadings has wide application potential in the production of petroleum-based diesel and green biodiesel with excellent low-temperature fluidity.

Polymorphs of a 1:1 salt of sulfadiazine and piperazine–relative stability, dissolution studies, pharmacokinetics and anti-meningitis efficiency

Two new salt forms of sulfadiazine (SDZ) and piperazine (PIP) were synthesized and characterized. Out of the two polymorphs (SDZ-PIP Ⅰ and SDZ-PIP II), SDZ-PIP Ⅱ is the more stable form at low temperature, room temperature and high temperature. The solution-mediated phase transformation result shows that SDZ-PIP II can transform into pure SDZ within 15 s in phosphate buffer at 37 °C, which leads to a loss in solubility advantage. The addition of 2 mg/mL PVP K30, a polymeric crystallization inhibitor, maintains the solubility advantage and permits supersaturation for a longer period of time. SDZ-PIP II showed 2.5 times the solubility of SDZ alone. The area under the curve (AUC) of SDZ-PIP II with 2 mg/mL PVP K30 was approximately 165% of that of SDZ alone. Moreover, SDZ-PIP II with PVP K30 was more effective than SDZ alone in treating meningitis. Therefore, the SDZ-PIP II salt improves the solubility, bioavailability, and anti-meningitis activity of SDZ.

Enteric coating of tablets containing an amorphous solid dispersion of an enteric polymer and a weakly basic drug: A strategy to enhance in vitro release

Recent work has highlighted that amorphous solid dispersions (ASDs) containing delamanid (DLM) and an enteric polymer, hypromellose phthalate (HPMCP), appear to be susceptible to crystallization during immersion in simulated gastric fluids. The goal of this study was to minimize contact of the ASD particles with the acidic media via application of an enteric coating to tablets containing the ASD intermediate, and improve the subsequent drug release at higher pH conditions. DLM ASDs were prepared with HPMCP and formulated into a tablet that was then coated with a methacrylic acid copolymer. Drug release was studied in vitro using a two-stage dissolution test where the pH of the gastric compartment was altered to reflect physiological variations. The medium was subsequently switched to simulated intestinal fluid. The gastric resistance time of the enteric coating was probed over the pH range of 1.6–5.0. The enteric coating was found to be effective at protecting the drug against crystallization in pH conditions where HPMCP was insoluble. Consequently, the variability in drug release following gastric immersion under pH conditions reflecting different prandial states was notably reduced when compared to the reference product. These findings support closer examination of the potential for drug crystallization from ASDs in the gastric environment where acid-insoluble polymers may be less effective as crystallization inhibitors. Further, addition of a protective enteric coating appears to provide a promising remediation strategy to prevent crystallization at low pH environments, and may mitigate variability associated with prandial state that arises due to pH changes.

Green and rapid and instrumental one-pot method for the synthesis of imidazolines having potential anti-SARS-CoV-2 main protease activity

The Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) is responsible for ongoing epidemics in humans and some other mammals and has been declared a public health emergency of international concern. In this project, several small non-peptide molecules were synthesized to inhibit the major proteinase (Mpro) of SARS-CoV-2 using rational strategies of drug design and medicinal chemistry. Mpro is a key enzyme of coronaviruses and plays an essential role in mediating viral replication and transcription in human lung epithelial and stem cells, making it an attractive drug target for SARS-CoV. The antiviral potential of imidazoline derivatives as inhibitors of (SARS-CoV-2) Mpro was evaluated using in-silico techniques such as molecular docking simulation, molecular dynamics (MD), and ADMET prediction. The docking scores of these imidazoline derivatives were compared to that of the N3 crystal inhibitor and showed that most of these compounds, particularly compound E07, interacted satisfactorily in the active site of the coronavirus and strongly interacted with the residues (Met 165, Gln 166, Met 165, His 41, and Gln 189). Furthermore, the results were confirmed by MD simulations after exposure to long-term MD simulations and ADMET predictions.

Effect of ion and protein concentration of Ps19, a shell protein from Pteria sterna, on calcium carbonate polymorph

Calcium carbonate is present in many biological structures such as bivalve shell, which is composed mainly of two CaCO3 polymorphs: calcite and aragonite. However, exist other forms of calcium carbonate like vaterite and amorphous calcium carbonate (ACC) that are not commonly reported. Polymorph selection is influenced by salt concentration, cofactor ions, and the presence of shell matrix proteins (SMPs) which regulates calcium carbonate deposition, among other factors. In this study, calcium carbonate crystallization in vitro of four different saline solutions at two molarities was evaluated with increased concentrations of the Ps19 protein, an insoluble extracted protein from the shell of Pteria sterna, previously described as a promotor of aragonite platelet crystallization. In vitro crystallizations showed that Ps19 is capable to induce aragonite and calcite deposition in a dose-dependent manner, but also vaterite under ciertan conditions, acting as a promoter and inhibitor of crystallization. The results contribute to understand how Ps19 control precipitation of calcium polymorphs in the growth of the prismatic and nacre layer of the shell of P. sterna.

Fabrication of b-oriented MFI zeolite membranes by a novel printing-transfer seed layer procedure.

Highly b-oriented MFI zeolite (abbreviated as BOMZ) membranes are attractive due to less grain boundary defects and straight channels normal to the substrate, enhancing selectivity and flux in membrane separation. Herein, we demonstrate a novel, effective and easily-amplified printing-transfer oriented-seed-layer technique to manufacture uniform BOMZ seed monolayer on porous supports. Furthermore, a facile and effective approach for the synthesis of highly BOMZ membranes by introducing poly(hexamethylene biguanide) hydrochloride as a twin crystal inhibitor during seeded growth is demonstrated. Well-intergrown BOMZ membranes (~650 nm thick) obtained on porous Al2O3 supports show a flux of 2.8 kg m-2 h-1 with a separation factor as high as 71 for pervaporation in the 60 oC feed of EtOH/H2O (5 wt%), which is much higher than those of random membranes. The developed seed assembly technique on porous supports underlines great potential for facile preparation of oriented seed layers on porous supports.

Development of convenient crystallization inhibition assays for structure-activity relationship studies in the discovery of crystallization inhibitors.

Kidney stone diseases are increasing globally in prevalence and recurrence rates, indicating an urgent medical need for developing new therapies that can prevent stone formation. One approach we have been working on is to develop small molecule inhibitors that can interfere with the crystallization process of the chemical substances that form the stones. For these drug discovery efforts, it is critical to have available easily accessible assay methods to evaluate the potential inhibitors and rank them for structure-activity relationship studies. Herein, we report a convenient, medium-to-high throughput assay platform using, as an example, the screening and evaluation of inhibitors of L-cystine crystallization for the prevention of kidney stones in cystinuria. The assay involves preparing a supersaturated solution, followed by incubating small volumes (<1 mL) of the supersaturated solution with test inhibitors for 72 hours, and finally measuring L-cystine concentrations in the supernatants after centrifugation using either a colorimetric or fluorometric method. Compared to traditional techniques for studying crystallization inhibitors, this miniaturized multi-well assay format is simple to implement, cost-effective, and widely applicable in determining and distinguishing the activities of compounds that inhibit crystallization. This assay has been successfully employed to discover L-cystine diamides as highly potent inhibitors of L-cystine crystallization such as LH708 with an EC50 of 0.058 μM, 70-fold more potent than L-CDME (EC50 = 4.31 μM).

Inhibition effect of novel amphiphilic poly(amino acid)s on methane hydrate

A series of novel amphiphilic poly(amino acid)s (PAAs) have been synthesized via the ring-opening polymerization of amino acid N-carboxyanhydrides, and their performance as kinetic hydrate inhibitors has been evaluated in high-pressure autoclaves by using methane gas. In the slow constant cooling tests, the PAAs with more hydrophobic groups lead to lower hydrate onset temperatures, and the best ones, such as 72% oxidized polymethionine, are with an inhibition effect about the same as the commercialized poly(N-vinyl pyrrolidone) (PVP) but worse than the powerful poly(N-vinyl caprolactam) (PVCap) at the concentration of 0.15 wt%. However, oxidized polymethionines are excellent hydrate crystal growth inhibitors since they have superior performance on retarding methane hydrate growth than both PVP and PVCap. In addition, molecular dynamics simulations have been used to insight into the inhibition mechanism of PAAs. It is found that the more hydrophobic PAAs are more efficient in preventing methane dissolution and water diffusion, consequently leading to the better hydrate inhibition performance.

MP10-17 OSTEOPONTIN PHOSPHOPEPTIDE MITIGATES UROLITHIASIS IN A DROSOPHILA MELANOGASTER MODEL

You have accessJournal of UrologyCME1 Apr 2023MP10-17 OSTEOPONTIN PHOSPHOPEPTIDE MITIGATES UROLITHIASIS IN A DROSOPHILA MELANOGASTER MODEL Polycronis Akouris, John Chmiel, Gerrit Stuivenberg, Wongsakorn Kiattiburut, Jennifer Bjazevic, Hassan Razvi, Bernd Grohe, Harvey Goldberg, Jeremy Burton, and Kait Al Polycronis AkourisPolycronis Akouris More articles by this author , John ChmielJohn Chmiel More articles by this author , Gerrit StuivenbergGerrit Stuivenberg More articles by this author , Wongsakorn KiattiburutWongsakorn Kiattiburut More articles by this author , Jennifer BjazevicJennifer Bjazevic More articles by this author , Hassan RazviHassan Razvi More articles by this author , Bernd GroheBernd Grohe More articles by this author , Harvey GoldbergHarvey Goldberg More articles by this author , Jeremy BurtonJeremy Burton More articles by this author , and Kait AlKait Al More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003225.17AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Kidney stone disease affects between 7 and 13% of the North American population and continues to burden global healthcare systems. The majority of kidney stones are calcium-based, with approximately 80% composed of calcium oxalate (CaOx). Despite advances in current preventative strategies, first-time symptomatic stone formers have an approximate 39% recurrence rate after 15 years. Thus, it is clear that more effective strategies are needed to prevent disease recurrence. Osteopontin (OPN) is a urinary protein that can inhibit the formation of CaOx monohydrate (COM) crystals in vitro. Numerous studies have confirmed that human and other mammalian OPN isoforms are potent inhibitors of COM crystallization. Despite this, the efficacy of these peptides as a supplement to prevent kidney stones has never been assessed in a living organism. We therefore sought to determine if a 16-residue synthetic OPN phosphopeptide (hereafter denoted as P3) could reduce CaOx stone burden and adhesion to mammalian kidney cells using in vivo and in vitro models, respectively. METHODS: To evaluate the effect of P3 on adhesion of COM crystals in vitro, synthetic crystals were allowed to adhere to Madin-Darby canine kidney (MDCK) cells in the presence of P3. An established Drosophila melanogaster model of CaOx-based urolithiasis was used to test the applicability of P3 to reduce stone burden in vivo. CaOx crystal burden and morphology were assessed using birefringence and confocal microscopy, respectively. RESULTS: P3 directly reduced the adherence of synthetic COM crystals to MDCK cells. Furthermore, oral supplementation of P3 significantly reduced CaOx burden in D. melanogaster. Confocal microscopy of crystals in D. melanogaster Malpighian tubules revealed that P3 was able to interact with COM crystals and alter morphology similar to previous in vitro studies. CONCLUSIONS: Altogether, this study demonstrates that a synthetic OPN phosphopeptide can directly mitigate CaOx-based urolithiasis formation in vivo by modulating crystal morphology. While in vitro evidence from simplistic models supports the inhibitory role of OPN phosphopeptides on CaOx crystal formation, this is the first study to directly illustrate that they can mitigate crystal formation in a complex living system. These findings suggest that OPN supplementation is a promising therapeutic approach and may be clinically useful in the management of recurrent CaOx urolithiasis in humans. Source of Funding: N/A © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e120 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Polycronis Akouris More articles by this author John Chmiel More articles by this author Gerrit Stuivenberg More articles by this author Wongsakorn Kiattiburut More articles by this author Jennifer Bjazevic More articles by this author Hassan Razvi More articles by this author Bernd Grohe More articles by this author Harvey Goldberg More articles by this author Jeremy Burton More articles by this author Kait Al More articles by this author Expand All Advertisement PDF downloadLoading ...

Kidney stone matrix proteins: Role in stone formation.

Stone formation is induced by an increased level of urine crystallization promoters and reduced levels of its inhibitors. Crystallization inhibitors include citrate, magnesium, zinc, and organic compounds such as glycosaminoglycans. In the urine, there are various proteins, such as uromodulin (Tamm-Horsfall protein), calgranulin, osteopontin, bikunin, and nephrocalcin, that are present in the stone matrix. The presence of several carboxyl groups in these macromolecules reduces calcium oxalate monohydrate crystal adhesion to the urinary epithelium and could potentially protect against lithiasis. Proteins are the most abundant component of kidney stone matrix, and their presence may reflect the process of stone formation. Many recent studies have explored the proteomics of urinary stones. Among the stone matrix proteins, the most frequently identified were uromodulin, S100 proteins (calgranulins A and B), osteopontin, and several other proteins typically engaged in inflammation and immune response. The normal level and structure of these macromolecules may constitute protection against calcium salt formation. Paradoxically, most of them may act as both promoters and inhibitors depending on circumstances. Many of these proteins have other functions in modulating oxidative stress, immune function, and inflammation that could also influence stone formation. Yet, the role of these kidney stone matrix proteins needs to be established through more studies comparing urinary stone proteomics between stone formers and non-stone formers.