Metal Ion-Coordinated Biomolecular Noncovalent Glass with Ceramic-like Mechanics

Open AccessCCS ChemistryRESEARCH ARTICLES23 Mar 2024Metal Ion-Coordinated Biomolecular Noncovalent Glass with Ceramic-like Mechanics Shuai Cao, Wei Fan, Rui Chang, Chengqian Yuan and Xuehai Yan Shuai Cao State Key Laboratory of Biochemical Engineering, Key Laboratory of Biopharmaceutical Preparation and Delivery, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing 100049 , Wei Fan State Key Laboratory of Biochemical Engineering, Key Laboratory of Biopharmaceutical Preparation and Delivery, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing 100049 , Rui Chang State Key Laboratory of Biochemical Engineering, Key Laboratory of Biopharmaceutical Preparation and Delivery, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing 100049 , Chengqian Yuan *Corresponding authors: E-mail Address: email protected E-mail Address: email protected State Key Laboratory of Biochemical Engineering, Key Laboratory of Biopharmaceutical Preparation and Delivery, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing 100049 and Xuehai Yan *Corresponding authors: E-mail Address: email protected E-mail Address: email protected State Key Laboratory of Biochemical Engineering, Key Laboratory of Biopharmaceutical Preparation and Delivery, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing 100049 Center for Mesoscience, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 https://doi.org/10.31635/ccschem.024.202303832 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Glass materials play a vital role in scientific research and engineering applications. Biomolecular noncovalent glasses (BNG), based on amino acids and peptides, have been proposed as the next-generation glass materials to meet the demand of a sustainability and circular economy. However, bulk BNG with remarkable mechanics and tunable photoluminescence are still rare due to the nature of weak noncovalent interactions and oversimplified molecular structures. Herein, we report the design and creation of metal ion-coordinated BNG (MIBNG) based on a simple amino acid derivative and metal ions. The obtained MIBNG exhibit ceramic-like mechanics, including the hardness, elasticity, and wear resistance, that are unattainable by the pure BNG counterpart. Such remarkable mechanics can be attributed to the enhanced noncovalent crosslinking network connectivity of biomolecules within MIBNG resulting from the incorporation of strong metal coordination interaction with hydrogen bonding and aromatic interactions. Moreover, fluorescence emission of MIBNG can be tuned feasibly through precisely modulating the types of metal ions coordinated. This study sheds light on the crucial role of multiple noncovalent interactions in the construction of BNG and advances the exploration and potential applications of BNG-based functional materials with tunable mechanical and optical properties in such fields as electronics and optics. Download figure Download PowerPoint Introduction Glass is a material with an amorphous structure that has a wide range of applications crossing a variety of fields. It is composed of a series of randomly packed atoms or molecules, lacking in long-range ordering.1,2 Its disordered nature endows glass with special physical and chemical properties, such as high transparency, uniform light scattering, and low thermal conductivity.3–5 The structure of glass can be changed and optimized by adjusting its composition and preparation process to achieve a specifuc performance on demand.6,7 There are many methods to prepare glass, including melting-quenching, sol–gel, and vapor deposition methods.8–10 The basic component of traditional inorganic glass is silicate, such as sodium calcium silicate, boron silicate, and aluminum silicate.11 With the progress in technology and changes in demand, innovations in glass materials continues to evolve, resulting in the emergence of new types of functional glass. For example, flexible glass and thin-film glass are gradually being applied in fields such as wearable devices and flexible displays.12,13 Nanostructured glass materials have special optical and magnetic properties, making them a research hotspot in the fields of nanotechnology and biomedicine.14 These developments provide more possibilities and prospects for the research and application of glass materials. Nevertheless, the development of green, ecofriendly and even biodegradable glass materials yet remains a formidable challenge. These are mainly manifested in the following aspects. First, the chemical stability of commonly used glass materials makes it difficult to degrade, leading to potential long-term environmental impacts.15 Second, glass materials cannot be decomposed and recycled through natural processes, further increasing their environmental burden.16 In addition, the production of glass materials often uses a large amount of energy and raw materials, leading to resource waste and environmental pollution.17 Biomolecular noncovalent glasses (BNG) based on amino acids and peptides have attracted much attention, due to their biocompatibility, biodegradability, and recyclability compared to commercial glass and plastic materials currently used.18,19 However, supramolecular materials connected by noncovalent interactions usually suffer from weak strength and mechanical stability.20–24 The mechanical properties of these materials are usually limited due to their weak noncovalent interactions. Therefore, further improving the performance of BNG and expanding their potential for applications remains an important research topic. Similarly, we enrich the functionality of existing glass materials by adding and doping other components to change the properties of the glass, resulting in specific functions and applications.25 For example, a coating of indium tin oxide can make glass conductive and suitable for optoelectronic devices or sensor applications.26 Adding rare earth ions, such as europium ions (Eu3+), to glass can achieve fluorescence effects, giving glass the characteristics of a fluorescent material.27 By adding antibacterial agents such as silver nanoparticles, glass can be endowed with antibacterial ability.28 This flexibility from the integration of functional components allows glass to be widely used in various fields such as electronics, optics, medicine, and so on.29,30 Inspired by the glass materials coordinated with other components, we successfully prepared a series of metal ion-coordinated BNG (MIBNG) through the introduction of metal coordination. A simple amino acid derivative, N-fluorene methoxycarbonyl-l-leucine (Fmoc-Leu-OH, abbreviated as Fml), was selected as one typical model building block, which coordinates with metal ions through carboxyl and carbonyl groups. The cooperation of multiple noncovalent interactions drives the formation and stabilization of MIBNG. The mechanics of MIBNG has been improved compared to the pristine BNG. The introduction of metal coordination interactions endows MIBNG with ceramic-like mechanics, including hardness, wear resistance, and elasticity that are difficult to achieve by the pure BNG counterpart. Moreover, by modulating the types of rare earth ions coordinated, precise regulation on the fluorescence of MIBNG was achieved. This study provides an effective strategy to fabricate multifunctional MIBNG with flexible mechanical and optical properties that holds broad application prospects in fields such as smart optics. Experimental Methods Materials Potassium hydroxide (KOH) was sourced from Beijing Chemical Co. Ltd. (Beijing, China), extra dry methanol was provided by Energy Chemical (Shanghai, China), and Fmoc-Leu-OH (referred to as Fml) was obtained from Energy Chemical. Anhydrous cobalt sulfate, anhydrous copper sulfate, and anhydrous zinc sulfate were supplied by Macklin (Shanghai, China). Lanthanum chloride heptahydrate, cerium chloride heptahydrate, europium chloride hexahydrate, terbium chloride hexahydrate, and lutetium chloride hexahydrate were all procured from the manufacturer, Energy Chemical. Synthesis of MIBNG KOH was dissolved in extra dry methanol at a concentration of 0.1 M. Subsequently, Fml was dissolved in the extra dry methanol solution containing KOH at a concentration of 100 mg mL−1. Once complete dissolution was achieved, taking the solution and dissolving the sulfate at the concentration of 0.0204 M allowed Fml molecules to fully interact with metal ions. The mixture was thoroughly blended to form a precursor solution. This precursor solution was then subjected to centrifugation in a high-speed centrifuge at 10,000 revolutions per minute (rpm) for 5 min. Following centrifugation, the supernatant was heated to 80 °C using a heat-collecting constant-temperature magnetic stirring tank to produce a viscous fluid. The resulting viscous fluid was further heated to 160 °C using a heated magnetic stirrer, then melted, cooled, and quenched at room temperature, thereby forming MIBNG. Characterizations Glass transition and melting temperature analysis Thermogravimetric analyzer combined with a differential scanning calorimeter (TGA-DSC) analyses were performed on all specimens using a TGA/DSC 3+ series instrument from Mettler Toledo (Greifensee, Zurich, Switzerland), and a DSC 1 instrument, also from Mettler Toledo. Before testing, two empty platinum crucibles with loose lids were used for baseline adjustments. One platinum crucible was filled with glass powders, while the other remained empty as a control. Using the TGA/DSC 3+ series instrument, the specimens underwent heating from room temperature to 773.15 K to determine Tm and Td. With the DSC 1 instrument, samples were subjected to controlled heating and cooling cycles. In Upscan 1, the platinum crucible containing the powders were heated from room temperature (T0) to a temperature (T1) exceeding Tm but below Td. Subsequently, quenching from T1 to a temperature (T2) lower than T0 occurred, followed by an isothermal hold at T1 for 5 min. In Upscan 2, the product was reheated from T2 to a temperature (T3) proximate to Tm, and Tg was recorded. To ensure sample uniformity, the platinum crucible was filled to less than 50% of its capacity. The heating and cooling rates were set at 10 K min−1. Throughout the measurements, samples were shielded with a nitrogen atmosphere. XRD measurement X-ray powder diffraction (XRD) analyses were conducted with a Rigaku SmartLab diffractometer (Rigaku, Tokyo, Japan), equipped with a 9 kW power source, utilizing a Cu filter and Cu Kα1 radiation (λ = 1.5406 Å) from Japan. Data collection involved scanning in the 2θ range from 10° to 40° at a rate of 10° min−1, with a 0.01 increment step. The specimens were carefully affixed to pristine silicon substrates. Polarized optical microscopy analysis Cross-polarized optical microscope (POM) was conducted using a BX53 polarized microscope system (Olympus, Tokyo, Japan). A 1.5 mg glass powder sample was carefully placed on a 30.0 mm diameter and 1.0 mm thick glass slide. The powder was subjected to controlled heating and cooling processes to achieve the vitreous state, and polarized microscopy images were subsequently acquired. Scanning electron microscope measurement This study involved the examination and observation of the surface morphology, texture, structure, and elemental composition of the samples using a Hitachi S-4800 II electron scanning microscope (Hitachi, Tokyo, Japan). The procedures involved attaching the glass powder specimen to conductive tape, gold-coating the sample for 2 min using a gold-sputtering apparatus, and examining the gold-coated sample with the scanning electron microscope (SEM) at an operational voltage of 10 kV to obtain surface morphology details. High-resolution electrospray ionization mass spectrometry measurement High-resolution electrospray ionization mass spectrometry (HR-ESI-MS) was performed using an Agilent Technologies (Santa Clara, California, USA) quadrupole time-of-flight (Q-TOF) mass spectrometer (model 6540) with electrospray ionization. Fourier transform infrared measurement Fourier transform infrared (FT-IR) spectra were acquired using a VERTEX 70v infrared spectrophotometer (Bruker, Karlsruhe, Baden-Württemberg, Germany). Each spectrum was generated through the accumulation of 32 scans over the spectral range from 4000 to 400 cm−1. Raman spectroscopy In-situ Raman spectroscopy was performed with the Renishaw RM 1000 micro-Raman system (Renishaw, London, UK), based in England. A 1200 line mm−1 grating was used for spectral acquisition in a backscattering geometry. The excitation wavelength was 532 nm, covering the range of 50–3500 cm−1. Specimens were directly placed under the microscope without any prior treatment, and data were subsequently collected. UV–vis absorption measurement Absorption spectra were acquired using a Lambda 1050+ spectrophotometer (Perkin Elmer, Waltham, Massachusetts, USA). The glass samples, approximately 2 mm in thickness, were oriented perpendicularly to the incident beam. Fluorescence spectroscopy Solid sample fluorescence spectra were obtained using an RF-6000 spectrofluorometer (Shimadzu, Kyoto, Japan). A 150-W Xenon arc lamp, supplied by Ushio Inc. (Tokyo, Japan), served as the light source. Scanning was conducted at a rate of 2000 nm min−1, with an excitation bandwidth of 1.5 nm and an emission light bandwidth of 1.0 nm. The specimens were placed on clean, flat quartz substrates. Nanoindentation The Young's modulus and hardness of the glass samples were determined using a G200 instrument equipped (Keysight, Santa Rosa, California, USA) with a three-sided pyramidal (Berkovich) diamond indenter tip, capable of penetrating up to 500 nm. The sample size for determining the Young's modulus and hardness was approximately 10 mm in length, 8 mm in width, and 0.8 mm in thickness. The specimens were encased in epoxy resin and progressively polished with progressively finer diamond suspensions. Nanoindentation tests were performed under dynamic displacement control, maintaining a constant strain rate of 0.05 s−1 over four cycles. Results and Discussion Initially, our focus was on preparing a viscous fluid containing metal ions and amino acids because the viscous fluid, similar to supercooled liquid, serves as a precursor for glass formation. In a standard procedure, Fml and metal ion salts were codissolved in methanol. The solvent was then evaporated at a temperature below the decomposition temperature (Td) of Fml to yield a viscous fluid. The thermal decomposition process of Fml powder was determined using a TGA-DSC. Fml clearly exhibited Tm at 429.1 K and Td at 530.9 K ( Supporting Information Figure S1). The large gap between Tm and Td provides the possibility to obtain stable viscous fluid coordinated with metal ions. Subsequent heating and quenching of this viscous liquid led to the formation of MIBNG (Figure 1a and Supporting Information Figure S2). The pristine Fml glass and MIBNG coordinated with different metal ions (e.g., Fml-Co, Fml-Cu, and Fml-Zn glasses) are displayed in Figure 1b. Figure 1 | Preparation and characterization of MIBNG. (a) Schematic diagram of the preparation process of MIBNG. (b) Appearance of different Fml glass MIBNG beads. (c) XRD patterns of Fml glass and MIBNG. (d) Bright (top) and polarized field (bottom) optical images of Fml glass and MIBNG. (e) DSC curves of Fml glass and MIBNG. (f) Optical transmittance of Fml glass and MIBNG. (g) SEM images of Fml glass and MIBNG. Download figure Download PowerPoint To ascertain the amorphous structure of MIBNG, we conducted XRD tests. The results revealed distinct diffraction peaks in the XRD pattern of Fml powder ( Supporting Information Figure S3), signifying its crystalline nature. However, XRD patterns of the glass samples displayed no discernible peaks, indicating the disordered atomic and molecular arrangement of MIBNG (Figure 1c). According to the Bragg equation,31 the spacing corresponding to the broad peak around 22° is nearly 0.40 nm, which can be ascribed to the local aromatic interactions between Fmoc rings.32 Subsequently, POM was employed to identify the crystalline and glassy samples (Figure 1d). The MIBNG displayed no detectable anisotropic birefringence, indicating their isotropic and amorphous characteristics. In contrast, the Fml powder exhibited strong optical anisotropy, suggesting the presence of an orientationally organized structure within the Fml powder ( Supporting Information Figure S4). Glass transition temperature (Tg) refers to the temperature range at which a material shifts from a rigid, glassy state to a pliable, rubbery state.33 This parameter is important in the realm of glassy materials, as it governs their characteristics across a range of temperatures and is associated with its practical utility in assessing material stability, processability, and suitability for various applications.34 Consequently, the investigation of Tg holds both theoretical and practical significance. To elucidate their glass transition properties, DSC measurement was employed to analyze the heat flow characteristics of Fml glass and MIBNG. The presence of distinct endothermic peaks in the second upscan of the DSC curves for these glasses (Figure 1e) indicated the occurrence of glass transitions at their respective temperatures. The Tg and heat capacity change (ΔCp) values for Fml glass and Fml-Co/Fml-Cu/Fml-Zn MIBNG were determined to be 310.4 K (ΔCp = 0.581 J g−1 K−1), 314.4 K (ΔCp = 0.549 J g−1 K−1), 315.4 K (ΔCp = 0.496 J g−1 K−1), and 313.0 K (ΔCp = 0.419 J g−1 K−1), respectively. The Tg/Tm ratios for the four samples were calculated to be 0.72, 0.73, 0.74, and 0.73, respectively, following the Kauzmann "2/3" law.35,36 Moreover, the similar values signified that the introduction of metal ions had little influence on the glass-forming ability of viscous liquid consisting of amino acids. Moreover, ΔCp exhibited a negative correlation with the degree of network connectivity and topological constraints.37 When compared to pristine Fml glass, the ΔCp of MIBNG decreased, suggesting an increase in network connectivity. Furthermore, the higher Tg values determined on the DSC curve indicated stronger noncovalent interactions and more stable noncovalent crosslinking network structure within MIBNG.38 DSC analysis of MIBNGs demonstrated that Tg values varied with the type of metal ions coordinated. This variation may be attributed to the difference in the coordination abilities of different metal ions with Fml. Moreover, compared to the glass obtained by direct melting-quenching of Fml powder, the glass obtained by methanol solvent evaporation method had a higher glass transition temperature ( Supporting Information Figure S5), indicating that the presence of methanol during glass formation endowed the glass with a more compact molecular arrangement and stronger intermolecular interactions. In the context of rapid quenching, a liquid can avoid crystallization and remain in a metastable supercooled state until it reaches the glass transition, resulting in a significant increase in viscosity during subsequent cooling.39 The second DSC upscans of Fml-Cu glass, measured at varying heating rates, demonstrated that with the increase in quenching rate ( Supporting Information Figure S6a), the Tg value also increased. This indicates that fast quenching rates are beneficial for the formation of MIBNG with a high Tg. Such a dependence can be understood by the fact that rapid quenching rates exceed the speed at which the system deviates for structural adjustments. This results in the occurrence of the glass transition at higher temperatures, leading to a higher Tg.40 There are significant variations in the relaxation behavior of liquids as they approach the glass transition, with dynamic properties showing rapid or gradual changes in response to minor temperature fluctuations. The fragility index (m) provides a straightforward means to quantify these differences.39 Various glass-forming liquids exhibit unique relationships between m and Tg.41 An analysis of these relationships was carried out by consolidating existing literature data from three categories of glass-forming liquids: polymers, inorganic materials, and metallic glass-forming agents. Take Fml-Cu glass as an example. Its m value was determined to be 24.0 ( Supporting Information Figure S6a,b), suggesting the tendency to form relatively brittle glasses.42 Moreover, its Tg and m values position Fml-Cu glass within the range of metallic glasses ( Supporting Information Figure S6c), similar to certain alloy glasses such as Ce70Al10Ni10Cu10.41 UV–vis transmission spectra of Fml glass and MIBNG were collected to determine their optical transmittance (Figure 1f). The pure Fml glass exhibited maximum transmittance, approximately 98.1% at a wavelength of about 400–800 nm, indicating high transparency. However, there was a slight decrease in transmittance after the introduction of metal ions. While the transmittance of all the MIBNG decreased within the range of 400–800 nm (indicating reduced transparency), these glass samples still maintained superior transparency compared to conventional glass and plastic.43 The enhanced light transmittance can be attributed to the smooth and flat microscale surface structure of these glasses, as confirmed by the absence of obvious textures, particle distribution, pores, and folds in the SEM image of the sample (Figure 1g). Analysis of the elemental distribution data revealed the presence of metal elements distributed on the surfaces of MIBNG samples, confirming the successful introduction of metal ions into the glasses ( Supporting Information Figure S7). To investigate the intermolecular interactions contributing to the formation and stabilization of MIBNG, FTIR and UV–vis absorption spectra of MIBNG together with pristine Fml powder and glass were collected and compared. For the crystalline Fml powder, the peak centered at 3331 and 3039 cm−1 were assigned to the N–H and O–H stretching vibrations (Figure 2a and Supporting Information Figure S8a). The peaks located at 1718 and 1694 cm−1 were attributed to the stretching vibrations of C=O in carboxyl groups, while the one around 1672 cm−1 corresponded to the C=O in the Fmoc group.44,45 The sharp peak centered at 1537 cm−1 arose from the N–H bending vibration.46 The presence of these well-defined peaks indicates ordered hydrogen bond arrangement within Fml powder. Regarding the pristine Fml and MIBNG glasses, these main peaks obviously became broadened, suggesting the existence of multiple hydrogen-bond modes within such glasses. Similarly, the Raman spectra of the glass samples also showed broadening relative to that of the Fml sample ( Supporting Information Figure S8b). After the formation of glass, the characteristic peak of N–H stretching vibration split into two bands with one redshifted and another blueshifted, while that of O–H stretching vibration blueshifted slightly. These results indicate the breakage of original hydrogen bonds involving N–H and O–H groups within the crystalline Fml powder and reformation of hydrogen bonds in glasses accompanying some free N–H. Notably, upon the introduction of metal ions, the band centered at 1706 cm−1 for the FT-IR spectrum of Fml glass redshifted to 1698 cm−1, while that located at 3310 cm−1 blueshifted to 3319 cm−1 (Figure 2a,b). These changes indicate the weakening of the hydrogen bonding interaction of C=O…N–H, which was further confirmed by the redshift of the amide II band from 1518 to 1513 cm−1.47 In contrast, the peaks centered at 3068 and 3042 cm−1 in Fml glass redshifted to 3066 and 3040 cm−1 in MIBNG respectively, suggesting the enhanced hydrogen bonding interaction of C=O…O–H within MIBNG. Additionally, the redshift of C=O stretching vibrations and high-resolution electrospray ionization mass spectra of MIBNG demonstrated the presence of metal coordination interactions (Figure 2c and Supporting Information Figure S9). Figure 2 | Molecular mechanism of the formation and stabilization of MIBNG. (a, b) FT-IR spectra of MIBNG together with pristine Fml powder and glass. (c) HR-ESI-MS spectra of MIBNG. (d) Raman spectra of MIBNG together with pristine Fml powder and glass. (e) Schematic illustration showing the multiple noncovalent interaction modes within MIBNG glass. Download figure Download PowerPoint Furthermore, we examined the Raman spectra, especially in the wavenumber range of 900–1060 cm−1 arising from the vibration of aromatic groups of pristine Fml powder and glass together with MIBNG (Figure 2d and Supporting Information Figure S8b). The sharp peak centered at 1005 cm−1 and three resolved peaks at 1050, 955, and 936 cm−1 indicated the ordered aromatic packing within the Fml powder.48 In contrast, the blueshift and broadening of the Raman peak at 1005 cm−1 suggested the coexistence of multiple aromatic packing modes within the Fml glass and MIBNG. The disappearance of peaks at 1050, 955, and 936 cm−1 indicated the absence of well-ordered π–π stacking, which is further supported by the disappearance of the shoulder at 279 nm in the UV–vis absorption spectra of Fml and MIBNG glasses ( Supporting Information Figure S8c). Taken together, the introduction of strong metal coordination interactions slightly weakened the hydrogen bonding interactions between Fml molecules and enhanced the nonspecific and disordered aromatic interactions between Fmoc rings. Cooperative effects of these noncovalent interactions drove the formation and preservation of the overall amorphous glass structure (Figure 2e). Next, we examined whether the introduction of metal ions can modify the mechanical properties of MIBNG through the nanoindentation measurement. Figure 3a depicts the representative load-displacement curves of pristine Fml glass and MIBNG. At the same load, the indentation displacement of pristine Fml glass is greater than that of MIBNG glasses, signifying higher indentation displacement resistance in the latter. This finding is due to the enhanced intermolecular interactions fostered by the introduction of metal coordination interactions within MIBNG. Figure 3 | Mechanical properties of MIBNG. (a) The load-displacement curve of MIBNG. (b) Young's modulus and hardness of MIBNG. Comparison of H3/E2 versus H (c) and elastic recovery rate versus H (d) in MIBNG and traditional materials, including ceramic and ceramic-based hybrids, metals and alloys, rubber, polymers and polymer-based hybrids.49 The elastic recovery rate of ordinary rubber is above 75%.49 Download figure Download PowerPoint The Young's modulus (E) and hardness (H) of MIBNG were determined based on the load–displacement curves.50 The results revealed variations in the elastic and hardness properties among these four glass samples (Figure 3b). In ascending order of magnitude: Fml glass exhibited the lowest Young's modulus and hardness, measuring 4.5 and 0.25 GPa, respectively, followed by Fml-Zn glass with values of 4.7 and 0.29 GPa, Fml-Cu glass with 5.3 and 0.31 GPa, and Fml-Co glass with the highest values at 5.8 and 0.38 GPa. The Young's modulus and hardness of each sample exceed those of poly(methyl methacrylate) (PMMA) organic glass.51,52 We found that H and E values of MIBNG can be tuned by the types of metal ions coordinated and are higher compared to those of pristine Fml glass, implying that the incorporation of metal ions effectively enhances the mechanics of MIBNG. In addition to H and E, the H3/E2 value represents a vital criterion for assessing the resistance to yield pressure.53 A comparative analysis of H3/E2 versus H between MIBNG and traditional materials, including rubber, polymer, cer