Concentrated Solutions Research Articles

Electrostatic Aspect of the Proton Reactivity in Concentrated Electrolyte Solutions.

Water-in-salt electrolytes with a surprisingly large electrochemical stability window of ≤3 V have revived interest in aqueous electrolytes for rechargeable lithium-ion batteries. However, recent reports of acidic pH measured in concentrated electrolyte solutions appear to be in contradiction with the suppressed activity of the hydrogen evolution reaction (HER). Therefore, the fundamental thermodynamics of proton reactivity in concentrated electrolyte solutions remains elusive. In this work, we have used density functional theory-based molecular dynamics (MD) simulations and the proton insertion method to investigate how the HER potential shifts in concentrated LiCl solutions under both acidic and alkaline conditions. Our results show that the intrinsic HER activity increases significantly with the salt concentration under acidic conditions but remains relatively constant under alkaline conditions. Moreover, by leverage over finite-field MD simulations, it is found that a determining factor for the HER activity is the Poisson potential of the liquid phase, which increases in concentrated electrolyte solutions with comparable values from both density functional theory and point-charge models.

On a Specific Method for Characterizing Ion Exchange Membranes to Assess Their Functionality in Salinity Gradient Power Generation Through Reverse Electrodialysis, Including the Effect of Temperature

Salinity gradient power (SGP) by reverse electrodialysis is a promising method for converting SGP into electricity. Instead of the conventional approach of using seawater and freshwater, an alternative method involves using highly concentrated salt solutions (brines) alongside seawater or brackish water. Key factors influencing SGP via reverse electrodialysis (SGP-RE) include the properties of ion exchange membranes, particularly their thickness. This paper outlines a practical experimental set-up that uses both a cation membrane (CM) and an anion membrane (AM). The system is configured with three compartments: two outer compartments filled with highly concentrated brine (HIGH) and a central compartment containing a lower concentration salt solution (LOW), akin to seawater. The compartments are separated by a CM on one side and an AM on the other. The ion transport rate from the HIGH compartments to the central LOW compartment allows for determining the overall ion transport coefficient for thin membranes. Measurements of ion flux and electrochemical voltage under dynamic equilibrium conditions also enable the estimation of the SGP-RE power density (W/m2). By controlling the temperature of the HIGH and LOW solutions, this experiment further investigates the significant impact of temperature on ion transport characteristics.

Carbon dioxide capture in sodium carbonate solution: Mass transfer kinetics and DTAC surfactant enhancement mechanism

Sodium carbonate solvent absorbent has been widely studied for CO2 reduction to deal with global warming because of its green, low cost, and non-corrosive advantages. However, in the application of sodium carbonate as an absorbent for CO2 capture, there is no unified cognition of the mass transfer process, which leads to the lack of guidance for the industrial large-scale process. Moreover, the mechanism of mass transfer enhancement of surfactants, which can effectively improve the mass transfer performance, has not been effectively explored in the literature. Based on this, this paper firstly adopts the molecular dynamics method to analyze the solution characteristics after surfactant addition and optimize the surfactant. Subsequently, a classical dissolved oxygen test method was used to measure the gas-liquid mass transfer coefficient for CO2 absorption into sodium carbonate solution. And based on this mass transfer coefficient measurement method, the mass transfer process of sodium carbonate solution with surfactant was analyzed. The results showed that the sodium carbonate solution with 5 wt% concentration and 10 wt% concentration at 30 °C did not satisfy the pseudo first-order fast chemical reaction kinetics assumption. To improve CO2 absorption mass transfer rate, dodecyl trimethyl ammonium chloride (DTAC) surfactant was introduced, which was improved by 119 % compared with non-enhanced solvent at 5 wt% concentration solution, and the assumption of pseudo first order fast chemical reaction was satisfied. After the introduction of surfactant, the barrier effect decreased the liquid phase mass transfer coefficient, but the Marangoni effect happened in the 5 wt% concentration of sodium carbonate solution, which enhanced the liquid-phase mass-transfer coefficient. This finding reveals the mechanism of mass transfer promotion of sodium carbonate by the surfactant DTAC, which is of great engineering significance for the application in the field of decarbonization after the introduction of surfactant.

High-salt-resistance aerogels composed of chitosan and anode powder for effective solar interfacial evaporation

Solar interfacial evaporation technology is widely utilized for seawater desalination and wastewater treatment, which are currently areas of significant research interest. The primary factors to consider when transitioning the evaporator from laboratory settings to practical applications are its mechanical stability and resistance to salt. In the present study, composite aerogels consisting of an anode powder (AP), polypyrrole (Ppy), and chitosan (CS) were produced by a conventional technique involving physical cross-linking and in situ growth. The resulting aerogel has a compact pore structure that enhances the scattering of light on its surface and increases the area available for evaporation. As a result, the material exhibits exceptional photothermal capabilities, with water evaporation rates and photothermal conversion efficiencies of 1.865 kg m−2 h−1 and 85.96%, respectively, when exposed to 1 sun illumination. Simultaneously, the aerogel exhibits exceptional efficacy in water purification and resistance to salt when employed for the treatment of heavy-metal wastewater, seawater, and highly concentrated saline solutions. Furthermore, the utilization of AP as a light-absorbing substance aligns with the principles of green chemistry by promoting the recycling and repurposing of waste materials. These results provide novel insights into the potential applications of lithium battery waste and the optimization of solar-interfacial-evaporator design.

Modified gum ghatti based hybrid hydrogel nanocomposite as adsorbent material for dye removal from wastewater

A hybrid hydrogel nanocomposite based on the polysaccharide-gum ghatti, has been made and evaluated as an adsorbent material for wastewater treatment. The nanocomposite is composed of a network of gum ghatti-graft-poly(2-acrylamido-2-methylpropane sulfonic acid) with magnetite nanoparticles embedded within. This functional material Ggh-g-PAMPS/Fe3O4 has been characterized by FTIR, TGA, SEM, EDS, XRD, BET and VSM techniques. The presence of magnetite nanoparticles imparted superparamagnetic property to the adsorbent material enabling its easy separation after use with an external magnet. The characterization data indicated mesoporous nature of the nanocomposite adsorbent with mean pore diameter of 4.9 nm. The nanoparticles imparted high surface area to the adsorbent material the value being 4.7 m2g−1 based on nitrogen adsorption experiments. The suitability of the material as an adsorbent for removal of cationic dyes from water was checked with two cationic dyes namely, rhodamine 6G and methylene blue. The maximum adsorption capacity of the nanocomposite Ggh-g-PAMPS/Fe3O4 towards rhodamine 6G and methylene blue were observed to be 403.2 and 427.8 mg g−1 respectively from their individual solutions of concentration 500 mg L−1. The pH dependence on swelling and surface charge indicated medium of pH of 7.0 as the ideal condition for effective adsorption. Freundlich isotherm model and pseudo second order kinetic model are observed to be the most befitting models to describe adsorption. Further, the thermodynamic studies revealed the adsorption to be a spontaneous and endothermic process. The desorption study portrayed the reusability of the adsorbent material. The excellent adsorption performance and magnetic nature of the developed nanocomposite suggests its potential application as an adsorbent material in wastewater treatment.

Calcium ion-triggered liquid-liquid phase separation of silk fibroin and spinning through acidification and shear stress

Many studies try to comprehend and replicate the natural silk spinning process due to its energy-efficient and eco-friendly process. In contrast to spider silk, the mechanisms of how silkworm silk fibroin (SF) undergoes liquid–liquid phase separation (LLPS) concerning the various environmental factors in the silk glands or how the SF coacervates transform into fibers remain unexplored. Here, we show that calcium ions, among the most abundant metal ions inside the silk glands, induce LLPS of SF under macromolecular crowded conditions by increasing both hydrophobic and electrostatic interactions between SF. Furthermore, SF coacervates assemble and further develop into fibrils under acidification and shear force. Finally, we prepare SF fiber using a pultrusion-based dry spinning, mirroring the natural silk spinning system. Unlike previous artificial spinning methods requiring concentrated solutions or harsh solvents, our process uses a less concentrated aqueous SF solution and minimal shear force, offering a biomimetic approach to fiber production.

Manipulating Aggregate Electrochemistry for High‐Performance Organic Redox Flow Batteries

Organic molecule in solutions is the energy storage unit in the organic redox flow batteries (ORFBs), of which the aggregation is acknowledged pivotal but has been rarely investigated. By establishing a pyridinium library, the manipulation over the aggregation in solutions is investigated at the molecular level. Both theoretical calculations and physiochemical methods are used to characterize the aggregate’s structure, and salient findings are as follows. First, the singly‐reduced monoradicals simultaneously aggregate in a concentrated solution, which is driven by the solvation effect, orbital overlap and dispersion interaction. Second, the aggregation can be manipulated by the molecular engineering strategy and counteracted by introducing either electrostatic repulsive force or twisted geometry. Third, the monoradical’s aggregation yields a decrease in the molecular singly occupied molecular orbital energy level and a linear scaling relationship with its thermodynamic potential. As a result, the increase in the concentration lowers the battery’s voltage, which counteracts its effort to increase the battery’s energy density. The anti‐aggregation is proven effective in breaking the scaling relationship and accordingly, a molecular strategy to manipulate aggregate electrochemistry is developed. This work provides physical insights into the electrolytic solution and chemical strategy for optimizing the flow battery.

Adsorption of Heavy Metals from Low Concentration Solutions onto Dried Chlamydomonas reinhardtii

Adsorption of Heavy Metals from Low Concentration Solutions onto Dried Chlamydomonas reinhardtii

Cochineal (Dactylopius coccus Costa) Pigment Extraction Assisted by Ultrasound and Microwave Techniques

Carminic acid is a natural pigment typically found in several insect taxa, including specific insects such as “grana cochinilla fina” in Mexico (Dactylopius coccus Costa). Commercially, it is also referred to as carmine, which is a more concentrated solution presenting as at least 50% carminic acid. To date, this dye has been used in the pharmaceutical, food and cosmetic industries. Unfortunately, one of the main limitations has to do with establishing the appropriate extraction and purification protocol. Currently, there is growing interest in developing eco-friendly and efficient pigment extraction processes for various applications. In this study, we compare the ultrasound- and microwave-assisted extraction versus with a conventional method to obtain carminic acid from cochineal. To do this, we considered three factors that influence the extraction process as independent variables: solvent volume, temperature and irradiation time. The optimization was carried out using the response surface methodology, employing a three-factor and three-level Box–Behnken experimental design. Carminic acid contents were quantified by UV–Vis spectroscopy, and extracts were evaluated by infrared spectroscopy to verify the integrity of the carminic acid molecule. The yield obtained by ultrasound-assisted extraction was 49.2 ± 3.25, with an efficiency of 31.3 mg/min, while microwave-assisted extraction showed a yield of 40.89 ± 2.96, with an efficiency of 27.3 mg/min. Both methods exceeded the extract yield (31.9 ± 3.4%) and efficiency (10.6 mg/min) obtained with the conventional method, demostrating that ultrasound- and microwave-assisted extraction are viable alternatives for obtaining carminic acid, with the potential to be scaled up to an industrial level.

Fixed-Bed Columns of Avocado (Persea americana Hass.) Seed and Peel Biomass as a Retainer for Contaminating Metals

This study evaluated the adsorbent capacity of the Ecuadorian avocado (Persea americana Hass.) seed and peel wastes as an alternative method for cadmium (Cd), mercury (Hg), lead (Pb), and nickel (Ni) ion removal from aqueous solutions. The laboratory microscale process was performed using fixed-bed columns containing 1 g of 600 μm particles of biomaterial pretreated with ethanol and ethylene glycol. Subsequently, metal solutions of different concentrations were eluted and measured by flame atomic absorption spectroscopy. Results showed that fixed-bed columns allow efficient adsorption of Pb (2.6 mg/g) with ethanol pretreatment. Lower adsorption capacity was achieved for Cd, Hg, and Ni ions. Favorable adsorption with high retention capacity was found for Pb+2 for the ethanol pretreated bio-adsorbent at higher concentrations (120 mg/L). Lower removal percentages were found for Cd+2, Hg+2, and Ni+2; Ni showed the lowest adsorption capacities and negative RL values, suggesting inefficient adsorbent development. Regeneration of Cd, Hg, and Pb ions from avocado peel and seed showed the highest recovery when 1 mol/L HCl solution was used. Regarding the adsorption isotherms, the Langmuir model was the one that best fit our data, demonstrating that adsorption takes place in a uniform monolayer and that each contaminant ion occupies a single site.

Use of Platelet Rich Plasma in Urological Conditions

Introduction: Platelet-rich plasma (PRP) has become an increasingly popular therapeutic tool across various medical specialties since its introduction in 1958. Defined as a concentrated solution of platelets and growth factors derived from autologous blood, PRP supports tissue repair and regeneration processes. PRP’s composition includes high concentrations of platelets and growth factors that facilitate angiogenesis, connective tissue remodeling, and cellular repair, making PRP a promising treatment option for complex urological conditions and beyond. Purpose of the study: This review aims to summarize the applications and efficacy of PRP in treating specific urological conditions such as erectile dysfunction, Peyronie's disease, urethral stricture, hypospadias, interstitial cystitis and urinary incontinence. Materials and Methods: To provide a comprehensive summary of current knowledge on this topic, a literature review of English-language articles, with an emphasis on recent publications, was conducted. The review utilized the PubMed database and included 51 studies accessed prior to October 2024. Conclusions: PRP therapy appears to be a promising, safe, and minimally invasive treatment option for several urological conditions. Studies suggest that PRP may benefit erectile function, reduce symptoms in Peyronie's disease, and improve outcomes in conditions related to the urethra and bladder, with minimal reported adverse effects. However, the lack of standardized PRP preparation protocols and large placebo-controlled trials poses a challenge to fully establishing its efficacy. Further research is necessary to confirm PRP’s effectiveness, optimize preparation and administration methods, and develop guidelines for its clinical application in urology.

Development of an Attenuated Total Reflectance-Ultraviolet-Visible Probe for the Online Monitoring of Dark Solutions.

Optical spectroscopy is a valuable tool for online monitoring of a variety of processes. Ultraviolet-visible (UV-vis) spectroscopy can monitor the concentration of analytes as well as identify the speciation and oxidation state. However, it can be difficult or impossible to employ UV-vis-based sensors in chemical systems that are very dark (i.e., have a high optical density), requiring exceedingly short path lengths (for transmission approaches) or an effective means of backscattering (for reflectance approaches). Examples of processes that produce highly absorbing solutions and that would benefit significantly from the diagnostic potential of optical sensors include used nuclear fuel recycling and molten salt systems with high concentrations of dissolved uranium. Utilizing an attenuated total reflectance (ATR) UV-vis approach can overcome these challenges and allow for the measurement of solutions orders of magnitude more concentrated than transmission UV-vis. However, determining ideal sensor specifications for various processes can be time-consuming and expensive. Here, we evaluate the ability of a novel ATR-UV-vis probe to measure very concentrated solutions of Co(II) and Ni(II) nitrate as well as organic dyes (methylene blue, acid red 1, and crystal violet). This sensor design provides a modular method for exploring possible "path lengths" by altering the length of the ATR fiber that was submerged within solution during spectral measurements. Measurements within the ATR sensor cell were compared to measurements gathered by transmission UV-vis of samples within a commercially available 1 cm optical cuvette. The ATR-UV-vis probe was capable of measuring absorbance of solutions with a chromophore concentration 600 times greater than that in the 1 cm cuvette. Advanced data analysis in the form of multivariate curve resolution (MCR) was used to analyze the speciation of methylene blue over a large concentration range. The application of this novel ATR-UV-vis probe to the investigation of dark solutions is a promising avenue for use in online monitoring of nuclear processes.

Diffusion and Viscosity in Mixed Protein Solutions.

The viscosity and diffusion properties of crowded protein systems were investigated with molecular dynamics simulations of SH3 mixtures with different crowders, and results were compared with experimental data. The simulations accurately reproduced experimental trends across a wide range of protein concentrations, including highly crowded environments up to 300 g/L. Notably, viscosity increased with crowding but varied little between different crowder types, while diffusion rates were significantly reduced depending on protein-protein interaction strength. Analysis using the Stokes-Einstein relation indicated that the reduction in diffusion exceeded what was expected from viscosity changes alone, with the additional slow-down attributable to transient cluster formation driven by weakly attractive interactions. Contact kinetics analysis further revealed that longer-lived interactions contributed more significantly to reduced diffusion rates than short-lived interactions. This study also highlights the accuracy of current computational methodologies for capturing the dynamics of proteins in highly concentrated solutions and provides insights into the molecular mechanisms affecting protein mobility in crowded environments.

Effect of different ratio KOH treatment on neem bark in the formation of activated carbon: Adsorption characteristics study

In this study, mature neem tree bark (NB) was chemically transformed into an activated carbon (NBAC) through different ratios (1:1, 1:2, 2:1, 1:3, 3:1) of KOH and NB biomass. The obtained Neem bark-activated carbons (NBAC-1, NBAC-2, NBAC-3, NBAC-4, and NBAC-5) were tested for methylene blue (MB) dye removal efficiency. The NBAC-1 was found to be highly effective against MB dye. The NBACs have a low Brunauer-Emmet-Teller (BET) surface area (10.8 m2/g) with surface functional groups dominated by -OH and -CO. It is thermally stable up to 700°C, and its surface elemental composition is mainly carbon, oxygen, and potassium. The adsorption characteristics against MB dye show that 99.15% of dye from 100 mg/L initial concentration solution was removed with 4 g/L NBAC-1 dosage in 200 min of contact time at 50°C solution temperature, and pH of 10 (pHzpc = 7.85), resulting in an adsorption capacity of 24.79 mg/g. Kinetic studies indicated that the adsorption process of MB dye utilizing NBAC-1 adhered to the linear pseudo-second-order (R2 = 0.9726) and nonlinear Elovich model (R2 = 0.9419), signifying chemisorption, alongside the nonlinear Weber-Morris model (R2 = 0.9231), highlighting the significance of mass diffusion of MB dye onto the NBAC-1 surface in multilayers. Isotherm investigations favored better conformity with the Freundlich model, exhibiting a higher R2 value of 0.999, suggesting a heterogeneous multilayer adsorption mechanism. Adsorption thermodynamics analysis inferred that the adsorption was feasible (∆G = -4.342 KJ/mol), endothermic (∆H = +50.0203 KJ/mol), and demonstrated a high affinity of NBAC-1 towards MB dye (∆S = +168.2255 J/K/mol). Recyclability of the NBAC-1 adsorbent was also conducted to check for its sustainable usage.

Bioprinting a resilient and transparent cornea stroma equivalent: harnessing dual crosslinking strategy with decellularized cornea matrix and silk fibroin hybrid.

Bioprinting a resilient yet optically transparent corneal tissue substitute remains a challenge. In this study we introduce an innovative methodology aimed at bolstering the mechanical and optical attributes of silk fibroin (SF) hydrogels, pivotal for the progression of cornea tissue engineering. We devised a unique eosin Y-based photoinitiator system to instigate di-tyrosine linkages within highly concentrated pristine SF solutions under green light exposure. This pioneering technique resulted in SF hydrogels fortified by dityrosine covalent bonds, preserving exceptional transparency and soft elastomeric qualities devoid of spontaneous transitions to stiff, opaque beta-sheet conformations. Furthermore, we synergistically combined SF with decellularized corneal matrix (DCM) hydrogel, leveraging photo-polymerization under green light followed by thermal gelation to establish resilient and stable gel formation. The ensuing dual crosslinked hybrid hydrogels exhibited superior mechanical and thermal resilience in comparison to dual crosslinked DCM hydrogels. The inclusion of SF in DCM further augmented the hydrogel's elasticity and shear recovery, positioning it as an optimal bioink for cornea bioprinting endeavors. During the extrusion printing process, photocrosslinking of the bioink superficially fortified SF and DCM polymer chains via di-tyrosine linkages, furnishing initial stability and mechanical fortitude. Subsequent post-printing thermal gelation further reinforced collagen chains through self-assembly. Notably, the bioprinted cornea constructs, housing human limbal mesenchymal stem cells (hLMSCs), manifested transparency, structural integrity, and optimal functionality, underscored by the expression of keratocyte proteoglycans. In summation, our engineered 3D constructs exhibit promising potential for in vivo applications in cornea tissue engineering, marking a significant stride forward in the field's advancement.

Synergistic effect of rice husk-derived activated carbon modified by Ni/Al-layered double hydroxides for lead removal from industrial wastewater

To enhance the adsorption efficiency of activated carbon for heavy metals, herein we synthesized a novel composite adsorbent by loading of nickel/aluminum layered double hydroxides (Ni/Al-LDH) onto a chemically modified Egyptian rice husk-derived activated carbon. The characterization techniques used for determining the chemical and surface structure of the prepared composite were including FTIR, XRD, SEM, and BET which confirmed the successful loading of LDH onto the prepared activated carbon surface. The modified activated carbon established significantly upgraded performance in eliminating lead ions from wastewater. Adsorption studies revealed that the process follows Freundlich isotherm and pseudo-second-order kinetics, indicating chemisorption as the rate-determining step. The maximum lead ions removal (using 50 ppm concentration solution) was 82% after 210 min at pH 7. The improved lead ions removal efficiency was attributed to the synergistic effect of the activated carbon’s surface chemistry and the LDH’s ion exchange properties. The presence of chelating groups like hydroxyl (–OH), amide (–CO–NH–), carboxylate (–COOH), and nitrogen-containing functional groups on the activated carbon surface, along with the hydroxide groups of the LDH, facilitates the complexation and adsorption of lead ions.

Grain boundary segregation spectrum in basal-textured Mg alloys: From solute decoration to structural transition

Mg alloys are promising lightweight structural materials due to their low density and excellent mechanical properties. However, their limited formability and ductility necessitate improvements in these properties, specifically through texture modification via grain boundary segregation. While significant efforts have been made, the segregation behavior in Mg polycrystals, particularly with basal texture, remains largely unexplored. In this study, we performed atomistic simulations to investigate grain boundary segregation in dilute and concentrated solid solution Mg–Al alloys. We computed the segregation energy spectrum of basal-textured Mg polycrystals, highlighting the contribution from specific grain boundary sites, such as junctions, and identified a newly discovered bimodal distribution which is distinct compared to the conventional skew-normal distribution found in randomly-oriented polycrystals. Using a hybrid molecular dynamics/Monte Carlo approach, we simulated segregation behavior at finite temperatures, identifying grain boundary structural transitions, particularly the varied fraction and morphology of topologically close-packed grain boundary phases when changing thermodynamic variables. The outcomes of this study offer crucial insights into basal-textured grain boundary segregation and phase formation, which can be extended to other relevant Mg alloys containing topologically close-packed intermetallics.

Germination and Seedling Performance of Watermelon as Affected by Chemo-priming

Seed priming is a very important operation for healthy germination and seedling growth. Though a growing body of literature, the report on seed priming on watermelon is hardly available. Thus an experiment was conducted to study the germination and seedling performance of three watermelon cultivars viz. Asian 2, Pakorea F1 and Black Red with six seed priming treatments such as hydropriming with distilled water, halopriming with 1.5N NaCl and 3% KNO3, osmopriming with 3% PEG (Polyethylene Glycol), oxidative priming with 0.1N HCl solution and control i.e. no priming. The seeds were primed overnight with the aforesaid liquids and were allowed to grow both in petridishes in dark condition within laboratory and in pot soil under natural condition in an open grill house. All three watermelon cultivars showed significant difference due to seed priming with aforesaid primers. Germination Index (GI) was found higher in Asian 2 and Black Red cultivars due to HCl priming and in Pakorea F1 due to NaCl priming, while priming with PEG and KNO3 inhibited the GI of respective cultivars. Seedling Vigor Index (SVI) was found higher in Pakorea F1 with HCl priming whereas lower in Asian 2 and Black Red cultivars with PEG priming. Both in dark (Lab) and light (open field) conditions, total seedling dry matter was found higher in Asian 2 and Black Red cultivars due to HCl priming and lower in Pakorea F1 due to PEG priming. Results showed that low concentrated (0.1N) HCl solution can be used as priming medium to enhance germination and seedling growth of watermelon seeds.

From Structure to Strength: Analyzing the Impact of Sulfuric Acid on Pig Bone Demineralization Through FTIR, LIBS, and AAS.

The present research aimed to investigate the demineralizing effects of sulfuric acid on pig bone. Alterations in collagen and phosphate contents and changes in the elemental composition of the bone during the 14-day-long immersion in sulfuric acid solutions of different concentrations were estimated using ATR-FTIR, LIBS, and AAS. FTIR spectra at amide I (1800-1600 cm-1) and phosphate ν1/ν3 (PO43-) (1300-900 cm-1) domains were scrutinized using the deconvolution method for monitoring changes in the protein secondary structure and mineral content. The results implicated sulfuric acid as a powerful demineralization agent and effective in targeting mineral components, such as hydroxyapatite, while leaving the collagen matrix relatively preserved with a complex secondary structure. Collagen maturity marker values gave valuable insights into the structural integrity of the bone. LIBS and AAS indicated changes in bone hardness; phosphorous-to-carbon ratio; and calcium, phosphorous, and magnesium content in the solutions left after the immersion period. The changes in the ratio of ionic-to-atomic calcium lines in the LIBS spectra indicated hardening of the bone, with increasing acid concentration and prolonged action, due to the deposition of calcium sulfate on the surface. The calcium concentration in the solutions decreased with increased acid concentration, while the change in phosphorus and magnesium concentrations was reversed.

Calcium phosphate nanoclusters modify periodontium remodeling and minimize orthodontic relapse

Orthodontic relapse is one of the most prevalent concerns of orthodontic therapy. Relapse results in patients' teeth reverting towards their pretreatment positions, which increases the susceptibility to functional problems, dental disease, and substantially increases the financial burden for retreatment. This phenomenon is thought to be induced by rapid remodeling of the periodontal ligament (PDL) in the early stages and poor bone quality in the later stages. Current therapies including fixed or removable retainers and fiberotomies have limitations with patient compliance and invasiveness. Approaches using biocompatible biomaterials, such as calcium phosphate polymer-induced liquid precursors (PILP), are an ideal translational approach for minimizing orthodontic relapse. Here, post-orthodontic relapse is reduced after a single injection of high concentration PILP (HC-PILP) nanoclusters by altering PDL remodeling in the early stage of relapse and improving trabecular bone quality in the later stage. HC-PILP nanoclusters are achieved by using high molecular weight poly aspartic acid (PASP, 14 kDa) and poly acrylic acid (PAA, 450 kDa), which resulted in a stable solution of high calcium and phosphate concentrations without premature precipitation. In vitro results show that HC-PILP nanoclusters prevented collagen type-I mineralization, which is essential for the tooth-PDL-bone interphase. In vivo experiments show that the HC-PILP nanoclusters minimize relapse and improve the trabecular bone quality in the late stages of relapse. Interestingly, HC-PILP nanoclusters also altered the remodeling of the PDL collagen during the early stages of relapse. Further in vitro experiments showed that HC-PILP nanoclusters alter the fibrillogenesis of collagen type-I by impacting the protein secondary structure and forming aggregates. These findings propose a new approach for treating orthodontic relapse and provide additional insight into the PILP nanocluster's structure and properties on collagenous structure repair.