1 Introduction

In recent years, there has been extensive research in the field of glass science, driven by the quest for advanced materials with multifunctional properties (Blanc et al. 2023). Glass, renowned for its exceptional versatility, has become the focal point of comprehensive research spanning various disciplines. This prominence is owed to the remarkable combination of inherent qualities of glass, including transparency, thermal resilience, mechanical robustness, and chemical inertness (Blanc et al. 2023; Lai et al. 2016). The ability to precisely tailor these properties to suit specific applications has led to the development of doped glasses. Doped glasses involve the introduction of distinct elements or compounds, resulting in significant alterations in the material’s characteristics. Borosilicate glasses (BSGs) have attracted considerable attention from the scientific and engineering communities (Lai et al. 2016). These glasses represent a blend of desirable attributes found in both silicate and borate glasses, combining network-forming elements, namely borate and silicate (Mansour et al. 2021). This unique composition allows borosilicate glasses to harness the advantageous characteristics of borate glasses, such as their low melting points, thermal stability, and optical transparency (Lai et al. 2016; Mansour et al. 2021). Simultaneously, they benefit from the enhanced mechanical and chemical stability of silicate glasses (Tostanoski et al. 2022).

Borosilicate glasses have found widespread utilization across various applications, encompassing pharmaceutical vessel construction, bioactive glass formulations, optical instrument fabrication (Mansour et al. 2021), display screen production (Tostanoski et al. 2022), and the creation of colored ceramics suitable for low-temperature processes (Mansour et al. 2021). It has been recognized that zinc ions (Zn2+), possessing a 3d10 electron configuration, do not exhibit probable 3d10–3d10 electronic transitions (Sayyed et al. 2018). Consequently, the incorporation of ZnO into borate glasses results in colorless glass formations (Sayyed et al. 2018; El-Daly et al. 2021). In fact, ZnO plays a dual role in such glasses, functioning both as a glass former (comprising ZnO4 structural units) and a glass modifier (comprising ZnO6 structural units) (El-Daly et al. 2021). Additionally, introducing ZnO through doping can effectively lower the glass's melting temperature while preserving its other essential properties. Furthermore, the coordination of Zn2+ ions can be adjusted to tailor the glass structure according to specific requirements for precise applications (El-Daly et al. 2021).

Borosilicate glasses play a pivotal role in various applications across fields such as optics, electronics, biomedicine, and engineering. The influence of CaO as a network modifier significantly impacts different glass properties (Ibrahim et al. 2023a). However, tailoring properties to specific applications often requires the incorporation of dopants, including Ga2O3, Fe2O3, V2O5, or Gd2O3, which enable precise control of the material's characteristics (El-Daly et al. 2021; Ibrahim et al. 2023a, 2023b; Boyjoo et al. 2016; Al-Hadeethi et al. 2019).

Gd2O3, in particular, has garnered considerable attention as a versatile dopant capable of inducing substantial transformations in the glass structure, physical properties, optical behavior, and bioactivity (Al-Hadeethi et al. 2019). Similarly, Ga2O3 is renowned for its remarkable ability to adopt various coordination states, allowing it to bond with different glass network formers and thereby orchestrate modifications in glass structure and properties (Rana et al. 2017). Including Ga2O3 in B2O3–SiO2–ZnO–CaO glasses holds promise for altering local atomic arrangements and coordination states (Rana et al. 2017). Consequently, these changes may lead to variations in glass density, thermal expansion coefficients, and glass transition temperatures. These modifications in glass network connectivity and rigidity can, in turn, influence mechanical properties like hardness and fracture toughness (Boyjoo et al. 2016; Ibrahim et al. 2023b; Al-Hadeethi et al. 2019; Rana et al. 2017). Therefore, understanding these structural variations comprehensively becomes essential for fine-tuning these glasses for specific applications. Furthermore, deliberately doping B2O3–SiO2–ZnO–CaO glasses with Ga2O3 can enhance various physical properties (Rana et al. 2017). This includes the modulation of electrical characteristics, such as conductivity and dielectric constants, making these glasses suitable for applications in electronics and sensing (El-Daly et al. 2021; Rana et al. 2017). The importance of optical properties in doped glasses cannot be overstated, especially in their relevance to photonics, optoelectronics, and telecommunications (Ballato and Dragic 2021). Including Ga2O3 in the glass matrix influences critical parameters, such as the optical bandgap, refractive index, and transparency range of B2O3–SiO2–ZnO–CaO glasses. Fine-tuning these parameters through deliberate doping provides a pathway to optimize these glasses for specific optical applications, whether UV filtration, laser emission, or waveguide functionalities (Ibrahim et al. 2023a; Al-Hadeethi et al. 2019; Ballato and Dragic 2021).

The bioactive materials that known as bioactive glasses (BGs), first created by Hench in 1969 (45S5), are considered to suggest attractive bioactivity and biocompatibility; Na2O, CaO, P2O5, and SiO2 system is the basis for the majority of them (Jones 2013). Bioactive glasses can be broadly categorized into three classes based on the representative former oxide present in the formulation, namely SiO2-based (silicate), B2O3-based (borate), and P2O5-based (phosphate) systems. Borate glasses have stronger reactivity than silicate glasses, which lead to faster bioactive kinetics (Brink et al. 1997). Other oxides may be added to its chemical composition to provide glass with particular uses (Tiama et al. 2023). Bioactive glasses have received the greatest attention in bone regeneration research due to their enticing bioactive qualities and their potential to bind with bone (Tripathi et al. 2016). So, these glasses promote bone and cell growth, and the immersion of bioactive glasses within the body produces a hydroxyapatite (HA) layer that links hard tissues and soft tissues (Kamal and Hezma 2018). In a mouse model, using bioactive borate glass coated with hydroxyapatite HCA nanoparticles was successful in wound healing (Chen et al. 2021). Previous research showed that as boron concentration increased, the precipitated hydroxyapatite (HA) increased, implying that the biological behavior substantially improved due to the integration of boron in bio-glass synthesis (Kamal and Hezma 2018; Chen et al. 2021). Furthermore, at a lower extracted dosage, B2O3 supplementation has favored the cell proliferation of human periodontal ligament cells (HPDLCs) (Bai et al. 2021; Ren et al. 2018).

On the other hand, borosilicate glass has been found to aid tissue infiltration, cell proliferation, and differentiation in vitro (Vallet-Regí et al. 2017). BGs are a unique biomaterial used for many biological applications, including bone regeneration, wound healing, and other medical applications such as cancer treatment (Jones 2013; Hench et al. 2014). Also, BGs have a high capacity for mineralization, good bone conductors, osteoclasts, and conductors, and they form strong interfacial bonds with soft and hard tissues (Ojansivu et al. 2018; Vallet-Regi et al. 2001). The borosilicate vitreous positively affected the adhesion of the HASC skeletal system. In many osteogenic indicators studied, borosilicate glass outperforms others in cell culture (Vallet-Regi et al. 2001; Doadrio et al. 2017). Depending on their composition, BGs may improve vascularization, wound healing, anti-inflammatory reactions, as well as bacterial growth (Zheng and Boccaccini 2017).

Additional therapeutic ions, such as Cu, Zn, Mg, Ag, Ga, and Ce, can be introduced into the silica network to offer specific biological activities to BGs (e.g., osteogenesis, angiogenesis, anti-inflammatory response, antibacterial activity) (Zhu et al. 2021). BGs can be modified to transport pharmaceuticals (antibiotics, enzymes, growth factors) and physiologically active ions for particular biomedical applications (Zheng and Boccaccini 2017; Zhu et al. 2021).

In contrast, inorganic materials have been widely used in tissue regeneration. The importance of adding therapeutic metal ions to BG for bone formation and angiogenesis was recognized in previous studies (Zheng and Boccaccini 2017; Zhu et al. 2021; Assis et al. 2022). Previous studies showed that gallium (Ga) ions improved the treatment of bone absorption, osteoporosis, and hypercalcemia associated with cancer (Zhu et al. 2021; Deliormanlı 2015). It also inhibits osteoporotic bone resorption without damaging osteoblasts (Collery et al. 2002). Also, it was the second metal ion that used in cancer treatment after platinum (Franchini et al. 2012). In metabolic bone, cancer, and infectious diseases, some gallium compounds might be employed as diagnostic and therapeutic techniques (Wren et al. 2013). It is a drug that has already received clinical approval and that showed abilities to lower blood calcium levels and prevent bacterial activity (Wren et al. 2013; Valappil et al. 2009). It is also crucial for recognizing the crystalline phases that precipitate in the glass materials (Mabied et al. 2022).

In this work, novel borosilicate glasses doped by Ga2O3 have been prepared. Furthermore, this study aims to investigate the effect of gallium ions on the local structure physical, optical, and bioactive properties of borosilicate glasses networks using XRD, experimental density, FTIR and UV–Vis-NIR, protein adsorption, and cell viability. In addition, we aim to understand the characteristics of Ga3+ doped borosilicate-based glasses for biomedical applications. Furthermore, the effect of Ga3+ upon the in vitro bioactivity of protein adsorption will be evaluated using Phosphate Buffered Saline (PBS) under static conditions, and the cell viability of all compounds (MTT) using Vero cells and a simulated body fluid (SBF) experiment will be assessed.

2 Experimental methods

2.1 Samples preparation

Borosilicate-based glasses, denoted as BSCZG, were synthesized using the melt-quenching method. The composition of these glasses was [50B2O3–5SiO2–15ZnO–(30-x)CaO–xGa2O3] where x ranged from 0 to 20 mol%. High-purity raw chemical materials, including B2O3, SiO2, ZnO, CaCO3, and Ga2O3, were meticulously weighed in the required mol% ratios and mixed well in a ceramic mortar. The resulting mixture was placed in a platinum crucible and melted at 1300 °C in an electric furnace for 2 h. Afterward, the molten BSCZG of each sample was cast between the copper disks at room temperature. The BSCZG glasses underwent a heat treatment process at 350 °C for 5 h to alleviate internal thermal stress. These procedures yielded transparent glass samples with a faint yellowish hue. The entire process of preparing the glass samples is visually summarized in Fig. 1.

Fig. 1
figure 1

The schematic diagram illustrates the methods used to obtain the BSCZG glasses in practice

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2.2 Characterization

X-ray diffraction patterns (XRD) of the BSCZG glasses, both as-prepared and after immersion in simulated body fluid (SBF), were acquired using a modern Bruker d8 advance diffractometer. The measurements were conducted with a Cu-Kα source (wavelength, λ = 1.542 Å), at 300 mA and 40 kV, covering a 2θ range from 5ο to 80ο.

Fourier Transform Infrared spectroscopy (FTIR) absorption spectra of the BSCZG glasses for the as-prepared samples and after immersion in SBF were recorded using a Bruker Vertex 70 spectrometer from Germany. The spectral resolution was set at 4 cm−1, and the wavenumber range was between 400 and 4000 cm−1.

The experimental density (ρexp) of the BSCZG glasses was determined using the Archimedes method with carbon tetrachloride (CCl4) as the immersion liquid, which has a known density of ρl = 1.592 g cm−3. The molar volume (Vm) was calculated based on the ρexp values and molar mass (Mw), with detailed procedures outlined in Sect. 3.3 of the results and discussions.

For optical measurements, polished glass plates with a surface area of about 1.5 cm2 and a thickness of about 1.5 mm were used for transmittance and absorbance spectroscopy. Prior to measurements, the BSCZG glasses underwent polishing using 80 and 180 grits. Optical absorption spectra were recorded using an Agilent Technologies Cary 5000 UV–Vis-NIR spectrophotometer in the wavelength range of 190–2500 nm, with a resolution of 2 nm.

2.3 Protein adsorption

The protein adsorption ability was investigated on sample surfaces as part of the physiological behavior research for the produced samples. Bovine serum albumin (BSA) was chosen as the representative protein for this study. Under controlled conditions of pH \(=\) 7.4 and a temperature of 37 °C, 0.2 g of BSA was introduced into 200 ml of phosphate-buffered saline (PBS). Within this solution, an additional 0.4 g of each sample (in powder form) was added to a 40-ml aliquot. The adsorption process was carried out for 1 h at 37 °C within an incubator. Following the adsorption period, the samples underwent a thorough washing procedure involving three rinsing cycles with PBS and distilled water. This process aimed to eliminate any unattached proteins and salt residues. Subsequently, the samples were dried at 37 °C. The FTIR technique was utilized to assess the capacity of proteins to bind to the surfaces of the samples.

2.4 Cell viability

The evaluation of cell viability for each drug was conducted through a 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) experiment using Vero cells. This assay relies on the reduction of tetrazolium salts into soluble formazan crystals, which are spectrophotometrically measurable. Initially, cells were seeded in a 96-well plate at 104 cells per well density and incubated overnight at 37 °C with 5% CO2. The following day, cells were individually treated with sequential doses of each chemical. After 48 h of incubation, 30 µl of a 5 mg/mL MTT solution was added to each well and incubated at 37 °C for 3 h. Subsequently, the cell culture medium was carefully aspirated, and 200 µl of dimethyl sulfoxide was added to each well to dissolve the insoluble formazan crystals. The absorbance at 570 nm was measured using a multimode microplate reader (CLARIO star Plus, BMG LABTECH, Germany). The CC50 (cytotoxic concentration at which 50% of cells are affected) was calculated using GraphPad Prism software through non-linear regression analysis with the log(inhibitor) versus normalized response-variable slope model.

2.5 Simulated body fluid

The samples were immersed in a simulated body fluid (SBF) solution at around 37 °C for one to fourteen days. According to Kokubo and Takadama (Quintero Sierra and Escobar 2019), SBF is produced by dissolving a mixture of salts, including NaCl, NaHCO3, KCl, K2HPO4.3H2O, MgCl2.6H2O, and Na2SO4, in distilled water and then buffering the mix with a tris and HCl solution to obtain a pH of 7.4. All of the chemicals were obtained from Sigma Aldrich.

3 Results and discussions

3.1 XRD

XRD patterns of BSCZG0 and BSCZG20 as-prepared samples showed a broad hump, confirming the amorphous nature of the prepared glass samples, as shown in Fig. 2.

Fig. 2
figure 2

XRD profiles of powder BSCZG0 and BSCZG20-glasses

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3.2 FTIR spectroscopy of as-prepared glass samples

FTIR is one of the most essential non-destructive techniques used in several science fields for studying the structure of the samples. It determines the functional groups of materials, such as glass samples (Catauro et al. 2015). Zhou et al. (Vukajlovic et al. 2021) informed that borosilicate glasses include boroxol rings like (B3O6) connected by the BO3 units. The present study focuses on the relation between BO3 and BO4 units and NBOs as a function of Ga2O3 content. Information about the formation of non-bridging oxygen NBOs by the transformation between BO4 and BO3 units can be obtained. Once glass modifiers (such as CaO) are introduced into borosilicate glass, the conversion of BO4 to BO3 causes the formation of (NBOs) (Vukajlovic et al. 2021). Figure 3a shows that five spectral regions that characterize the FTIR absorption spectra of BSCZG. The absorption band within region V was observed between (1800–1600 cm−1) this may be attributed to the hydroxyl group (OH−) (Vukajlovic et al. 2021; Ibrahim et al. 2023c). The vibration bands in region IV are between 1600 and 1228 cm−1, related to BO3 units (Catauro et al. 2015; Vukajlovic et al. 2021). Region III represents the distinctive vibrations of BO4 units (Vukajlovic et al. 2021) that observed at (1228–800 cm−1). Region II refers to the configuration of bending modes in BO3 units in the wavenumber range (800–600) cm−1, which contains the B-O-B bending modes (Ibrahim et al. 2022). In region I, the absorption bands that observed in the wavenumber range of (600–400 cm−1) are related to the vibrations of metal cations such as Ca2+, Zn2+, and Si–O–Si (Wren et al. 2013; Ibrahim et al. 2022). Depending on the change in the composition of the BSCZG, these five zones shifted to higher wavenumbers, as Ga2O3 content was increased. It combines superposition and smaller absorption bands that are contained in wide band. These broad bands may be divided into small bands, each small band belonging to a specific structural group. The deconvolution of these spectra using Origin software’s “many peaks fit” method, to extract the five areas into discrete bands, as shown in Fig. 3a.

Fig. 3
figure 3

a FTIR spectra of BSCZG glasses with ‘x’ of 0, 5,10, 15, and 20 mol% Ga2O3 content, b Deconvoluted infrared bands of the sample doped with Ga2O3 = 5 mol%, c Variation of the N4 and N3 of BSCZG-glass

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Table 1 lists the peak positions (xc) and the assignments for each peak obtained by the deconvolution process. Furthermore, a detailed recognition of the deconvoluted bands leads to the following assignments about the structural changes that caused by increasing Ga2O3 content. The small absorption peak at 422 cm−1 may be ascribed to Ca–O vibrations (Collery et al. 2002; Catauro et al. 2015). According to Fig. 3a and Table 1, the peak shifted to a lower wavenumber, and its intensity decreased with decreasing CaO content from 30 to 10 mol%. The absorption peak at 462 cm−1 is due to Si–O–Si bending vibration in SiO4 tetrahedra (Vukajlovic et al. 2021; Ibrahim et al. 2022; Zhou et al. 2021). This peak shifted slightly toward a smaller wavenumber as Ga2O3 content was increased and its intensity decreased from BSCZG0 to BSCZG15, while it increased at BSCZG20. Due to the in-plane bending of the BO3 unit (Ibrahim et al. 2022), a small peak at 585 cm−1 appeared as Ga2O3 was increased. This peak is ascribed to the asymmetric vibration of Si–O–Si (Zhou et al. 2021).

Table 1 Band assignment for FTIR spectra of BSCZG -glasses
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The strong absorption peak at 684 cm−1 is allocated to B–O–B bending vibration in symmetric BO3 triangles (Catauro et al. 2015; Vukajlovic et al. 2021; Ibrahim et al. 2023c, 2022). Moreover, Fig. 3a shows that the intensity of this peak increased gradually with increasing Ga2O3 content. Additionally, a significant peak in this study was observed in Fig. 3b at 886 cm−1, which is ascribed to the stretching of BO4 units and starching vibration of non-bridging oxygens (NBOs) of BO4 groups as well as Si–O–Si symmetric vibrations (Catauro et al. 2015; Ibrahim et al. 2022). According to the deconvolution data, the area under this peak decreased gradually with increasing Ga2O3 content, which means that the amount of NBOs in BO4 decreased. A peak at 981 cm−1 is ascribed to the vibration of B-O bonds in the BO4 unit (Catauro et al. 2015). A strong absorption peak observed at around 1002 cm−1 is attributed to bending vibrations of B-O bonds in BO4 units from tri-, tetra-, and Penta-borate groups (Vukajlovic et al. 2021; Ibrahim et al. 2022). The center of the peak shifted to a higher wavenumber from 1002 to 1024 cm−1 with the increasing content of Ga2O3 from 0 to 20 mol%. The absorption peak observed at 1091 cm−1 may be ascribed to penta-borate units (Catauro et al. 2015; Vukajlovic et al. 2021). The center of the peak shifted to a higher wavenumber with increasing Ga2O3 content. Hence, the absorption peak located in the range (1241–1265 cm−1) is essential for understanding the variation in the structure of the glass matrix. Based on the data, this peak is related to the B-O vibrations of non-bridging oxygens (NBOs) in the BO3 units (Catauro et al. 2015; Vukajlovic et al. 2021; Ibrahim et al. 2023c, 2022), and its intensity increases with increasing Ga2O3 content. Additionally, the data obtained after the band disintegration showed that the area under peak increased with the increasing Ga2O3 content, this is reflected in the possibility of producing NBOs markedly. A strong absorption peak at 1338 cm−1 is attributed to the B-O vibrations of bridging oxygens within the BO3 units (Vukajlovic et al. 2021; Ibrahim et al. 2022). The center of the peak was shifted to a lower wavenumber by adding Ga ions to the glass matrix from 1388 to 1379 cm−1, as shown in Table 1. Also, the peak intensity was increased with the increasing Ga2O3 content from 0 to 20 mol.

On the other hand, based on the results summarized in Table 1 and shown in Fig. 3b, one can calculate N4 using the following equation (Vukajlovic et al. 2021; Ibrahim et al. 2022). During N4 calculations, we did not consider the relative areas of individual bands less than 886 cm−1.

$$N_{4} = \frac{{A\left( {BO_{4} } \right)}}{{A\left( {BO_{4} } \right) + A\left( {BO_{3} } \right)}}$$
(1)

where A(BO4) is the total area under the absorption peaks at (1228–800 cm−1) and A(BO3) is the total area under the absorption peaks at (1600–1228 cm−1 and 800–600 cm−1).

From Fig. 3c, we notice the linear decrease in N4 from 43.25 to 38.75% with the increase of the Ga2O3 content. As a result, the continuous replacement of Ga2O3 by CaO causes a decrease in the N4 ratio (as shown in Fig. 3c) and, as a result, a steady increase in NBOs in the glass matrix could be observed. The significant drop in the N4 ratio with increasing Ga2O3 concentration means that BO4 groups decrease and BO3 units increase causing the generation of NBOs in the glass matrix.

3.3 Physical properties

Density is one of the simple and easy method by which we know some information about changes in a material due to changing chemical composition. As it is a macroscopic method, it is probable to identify the structural variations in the glass network. Figure 4 shows the increase in experimental density (ρexp) and the molar volume (Vm) with the increase of Ga2O3 content.

Fig. 4
figure 4

Variation of the experimental density (ρexp) and molar volume (Vm) as a function of Ga2O3 content for all BSCZG -glasses

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A gradual increase in both (ρexp) and (Vm) from 2.70 to 3.14 g cm−3 and from 24.66 to 29.58 cm3 mol−1, respectively, with the increase of the Ga2O3 content. The approximate increase in the (ρexp) of the sample that is free of Ga2O3 is 10, 12, 14, and 16% for BSCZG5, BSCZG10, BSCZG15, and BSCZG20 glasses, respectively. Since Ga2O3 has a greater molar mass than CaO (187.44 g. mol−1 vs. 56.07 g mol−1), it was found that the density increases as the amount of Ga2O3 in the glass matrix was increased. As a result, the significant increase in density can be attributed to this reason (Doadrio et al. 2017; Collery et al. 2002). Also, the values of (Vm) were increased with the replacement of CaO with Ga2O3 in the glass network (Collery et al. 2002). The approximate increase in the (Vm) of the BSCZG0 glass sample is 2, 7, 13, and 20% for BSCZG5, BSCZG10, BSCZG15, and BSCZG20 glasses, respectively. The increase in molar volume is likely due to the following possibilities: (1) Ga2O3 replaced CaO, which had one oxygen ion, with three oxygen ions, increasing the number of oxygen ions in the glass network. (2) According to the previously presented FTIR results, we can correlate the gradual increase of Vm for BSCZG-glasses with the increase in NBOs (alteration of BO4 to BO3 group), causing the formation of a glassy network that tends to be open structure (Vukajlovic et al. 2021). Therefore, based on (1) and (2) the increase in the Vm of BSCZG-glasses with Ga2O3 content. Furthermore, the ions (N) concentrations are calculated from the Vm via the formula in Table 2. It decreased from 2.44 × 1022 to 2.03 × 1022 (cm−3), proportional to the increase of Ga2O3 content in the glass network. Also, this decrease can be ascribed to the increase in (Vm) values, as shown in Table. 2. Additionally, the interatomic distance values (ri) are computed using the formula in Table 2. The ri values were increased from 4.26 (Å) to 5.11 (Å) with more increase of Ga2O3 content from 0 to 20 mol%. This may represent the glass network's tendency to the open structure. Based on the calculated result of Vm and ri are in good agreement with the results obtained by FTIR, whereas the increase in Ga2O3 content caused the increase in NBOs. In addition, the optical basicity (ʌth) denotes the capability of oxide glasses to transport negative charges from the glass network to the probe ions (Ibrahim et al. 2023c, 2022; Zhou et al. 2021; Farouk et al. 2020). An oxide glass' acidic-base nature is determined by its electronegativity, using the equation in Table 2 (Abd El-Fattah et al. 2017). To begin, we multiply the (mol%) of oxide i (xi) through its electronegativity (χi) and add them together to get the electronegativity of each mixture. The average electronegativity (χavg) acquired the optical basicity through replacement in the equation provided in Table 2. The electronic polarizability (\(\alpha_{0}^{ - 2}\)) of oxide was a feature that lends to the electronic and optical applications of the materials (Farouk et al. 2020; Abd El-Fattah et al. 2017). The computed values of (\(\alpha_{0}^{ - 2}\)) are known by the empirical method; Table 2. It was observed that the values of \(\alpha_{0}^{ - 2}\) and (∧th) increased as a function of increasing Ga2O3 content. According to Zhou et al. (2021); Abd El-Fattah et al. 2017), as the single bond strength decreases, which is lower for Ga2O3 (285 kJ mol−1) than for CaO (464 kJ mol−1), the values of optical basicity may be increased (Farouk et al. 2020; Abd El-Fattah et al. 2017; Ibrahim and Sadeq 2021).

Table 2 Some physical properties of BSCZG -glasses
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The average values of \(\alpha_{0}^{ - 2}\) and ∧th for BSCZG glasses show a slight increase with increasing Ga2O3/CaO ratio, as the basic oxide of both CaO and Ga2O3 are close together, since (Λ(no) = 1.00 for CaO) and (Λ(no) = 0.71 for Ga2O3) (Abd El-Fattah et al. 2017). The minor increase in ∧th and \(\alpha_{0}^{ - 2}\) of the BSCZG glasses with increased Ga2O3 concentration might indicate an increase in electron localization and, as a result, an increase in localized donor pressure of the BSCZG-glasses network (Catauro et al. 2015; Abd El-Fattah et al. 2017).

3.4 Optical properties

The transmission spectra of BSCZG glasses in the UV, visible, and NIR ranges are shown in Fig. 5. Transmission results show that the BSCZG0 glass, which is free of Ga2O3, exhibits transmittance in the 400–1200 nm range. This range is typical of the visible and near-infrared spectra, roughly 53% at 1200 nm, indicating a reduced transparency degree for the BSCZG glasses. Meanwhile, after adding Ga2O3 to the glass matrix, the transparency of BSCZG glasses increases. As a result, the values of transparency were increased to 72% at the BSCZG20 glass. It is known that there are no transmission peaks in infrared and visible absorption spectra in borosilicate glasses, this is one of their most distinguishing features (Ibrahim and Sadeq 2021).

Fig. 5
figure 5

UV–Visible-NIR optical transmittance versus wavelength for BSCZG- glasses

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The transition between the valance and conduction bands, i.e., the energy gap, causes the absorption edge, or cut-off, in the near UV range. The absorption edge wavelength shifts towards the redshift as the Ga2O3 content in the BSCZG glasses increases.

The absorption coefficient (α) can be computed by the equation (Valappil et al. 2009):

$$\alpha \left( \upsilon \right) = \frac{1}{t}\log \frac{{I_{o} }}{I}$$
(2)

where \(\frac{Io}{I}\) corresponds to the absorbance near the edge, and t is the thickness of the glass sample.

By the Mott-Davis relation, the optical band gap can be calculated based on absorption coefficients (Sistla and Seshasayee 2004):

$$\alpha \left( \upsilon \right) = B \frac{{(h\upsilon - E_{opt} )^{z} }}{h\upsilon }$$
(3)

There are potential values of (z) that can be equal to 2, 1/2, 3, and 3/2, respectively, for indirect allowed, directly allowed, and indirectly forbidden transitions. The energy and momentum of an electron in an optical transition are retained equally in crystalline semiconductors, whereas only the energy is conserved in amorphous materials. The absorption of photons around Eopt in indirect band gap semiconductors, such as specific glasses, necessitates phonons' absorption and/or emission during absorption. The value for (z) in our glassy system is equal to 2, corresponding to the indirect transition (Zhou et al. 2021; Abd El-Fattah et al. 2017).

The values of Eopt are calculated by extrapolating the linear part of the spectrum, when (\(\alpha h\upsilon )^{0.5}\) is plotted against photon energy (h \(\upsilon\)) in (Fig. 6a–c). In Fig. 6d the values of Eopt are presented with increasing Ga2O3 concentration in BSCZG-glasses, and Eopt values rapidly decreased from 3.27 eV to 3.08 with increasing Ga2O3 from 0 to 20 mol%. A decrease in Eopt values is explained by an increase in NBOs in BBSCZG glasses with the increasing Ga2O3 content. Moreover, increasing values of \(\alpha_{0}^{ - 2}\) and ∧th with increasing Ga2O3 additions can promote such a decrease in Eopt values. Furthermore, it was found that the obtained Eopt values were within the range of semiconductors.

Fig. 6
figure 6

The optical band gap of a BSCZG0, b BSCZG5, c BSCZG20, and d the variation of the optical band gap (EOpt) and the optical band tail (EU) for BSCZG-glass samples

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The band tail width of absorption spectra can potentially reveal information regarding a probable variation in the glassy matrix (Ibrahim and Sadeq 2021). EU is linked to \(\alpha \left( \upsilon \right)\) by an exponential relationship for lower values of the absorption coefficient band tail (Ibrahim and Sadeq 2021; Sayyed et al. 2022):

$$\alpha \left( \upsilon \right) = \alpha_{0} {\text{exp}}\left( {\frac{h\upsilon }{{E_{U} }}} \right)$$
(4)

where EU is the Urbach energy, α is a constant, and hυ is the photon energy. The width of the band tail of the localized states in the band gap is reflected by the Urbach energy. By plotting a relationship between lnα and hυ the value of EU can be determined by the slope in the above relationship. A summary of the calculated values is provided in Table 3. The values of EU increase from 0.20 to 0.25 eV with increasing Ga2O3 content from 0 to 20 mol%., as shown in Fig. 6d. These results are in good agreement with the results obtained from the FTIR part, where the results showed an increase in NBOs, increasing the localized state developed by the Ga2O3 amounts. Therefore, it is evident that gallium's ions addition make these glass samples a promising material for optoelectronic applications.

Table 3 Optical band gap (EOpt), optical band tail (EU), refractive index(n), and dielectric constant (εo) of BSCZG-glasses
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The refractive index (n) is particularly essential for optical glasses applications. The energy band gap and the density of oxide glasses are connected to the linearity of the refractive index, and n may be computed using the equation (Sayyed et al. 2022).

$$n_{r} = \frac{{\rho_{\exp + 10.4} }}{8.6}$$
(5)

The refractive index (εo = n2) (Sadeq and Ibrahim 2021) may be used to compute the optical dielectric constant. As a result, the Penn model can be stated as a function of the refractive index. The refractive index and optical dielectric constant of the BSCZG glasses vary with Ga2O3 content, as shown in Table 3. The refractive index (n) increased linearly from 1.52 for Ga-free glass to be 1.57 for high Ga2O3 concentration. This demonstrates that the structure is more open to the glassy system, which coincides with the higher NBOs in the FTIR measurements.

In context, the dielectric constant of BSCZG glasses increased from 2.32 to 2.48 with increasing Ga ions content in the glass matrix from 0 to 20 mol%. As shown in Table 3, a decrease in the optical bandgap results from the increase in the optical dielectric constant. The optical band gap and refractive index results indicate that gallium ions in these samples are optimal materials for optoelectronic applications.

3.5 After simulated body fluid SBF

XRD patterns of BSCZG glass samples, after immersion in simulated body fluid (SBF) for 3, 7, and 14 days, are depicted in Fig. 7a–c, respectively. The analysis of these XRD patterns reveals the emergence of hydroxyapatite (HA). Notably, the distinct HA peak is not observed in the BSCZG samples, except for BSCZG15 and BSCZG20. The observed linewidth peak at 2θ of 26ο aligns with Card No. 98-008-2291 of the Inorganic Crystal Structure Database (ICSD). This observation is consistent with findings reported in numerous literature sources (Zhou et al. 2021; Sadeq and Ibrahim 2021).

Fig. 7
figure 7

XRD patterns of BSCZG samples after immersion in SBF a 3 days, b 7 days, and c 14 days

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On the other hand, the FTIR results confirmed hydroxyapatite (HA) formation in the BSCZG samples following immersion in simulated body fluid (SBF), as illustrated in Fig. 8. A noticeable change in the crystallization rate is observed between BSCZG15 and BSCZG20 as increasing the immersion time. This phenomenon can be attributed to the stepwise process of hydroxyapatite formation, involving ion exchange and material rearrangement, aligning with previously published findings (Woo et al. 2007). The samples were immersed in SBF solution, maintained at approximately 37 °C, for durations ranging from 1 to 14 days. With increasing immersion time, new peaks emerged in the FTIR spectra within the 550–610 cm−1 range, as depicted in Fig. 8a–c.

Fig. 8
figure 8

FTIR spectra of BSCZG glasses with ‘x’ of 0, 5, 10, 15, and 20 mol.% Ga2O3 content after immersion SBF a 3 days, b 7 days, and c 14 days

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Specifically, two bands at 570 cm−1 and 610 cm−1 (corresponding to P-O bands) signify the antisymmetric vibration mode of P-O in amorphous calcium phosphate, indicating HA formation after immersion in SBF (Sayyed et al. 2022; Sadeq and Ibrahim 2021; Farag et al. 2022). Around 560 cm−1, a single peak or a split peak became evident for these samples. The presence of crystalline calcium phosphates, including hydroxyapatite (HA), is signaled by this region, which is particularly distinctive for apatite and other phosphates. It corresponds to P-O bonding vibrations within a PO34− tetrahedron. According to Videau and Dupuis, a single peak in this region indicates the formation of non-apatite or amorphous calcium phosphate (ACP), typically considered a precursor to hydroxyapatite (Sayyed et al. 2022; Sadeq and Ibrahim 2021). As Jones, Sepulveda, and Hench described, apatite PO34− groups exhibit distinct split bands at 530 and 610 cm−1 (Farouk et al. 2020). It is plausible that BSCZG glasses with higher concentrations of Ga2O3 may contain more apatite and other phosphates, thereby increasing the network's apatite content.

3.6 Proteins adsorption

The behavior of protein adsorption is significantly influenced by biomaterials' chemical composition and surface charge (Woo et al. 2007). This influence arises from reactions between functional groups present on proteins and those on the surfaces of glass samples. To assess the adsorption behavior of the produced samples, they were immersed for 1 h at 37 °C in a plastic beaker containing a 10 mg mL−1 solution of bovine serum albumin (BSA) dissolved in phosphate-buffered saline (PBS). Figure 9 and Table 4 illustrate the disintegration of the amide I and amide II bands in the spectrum due to BSA adsorption at the interfaces of the samples. Specifically, in the BSCZG0 sample, the amide I band initially appears at 1738 cm−1, while in BSCZG20, this peak shifts to a higher wavenumber that is observed at 1743 cm−1 (Bouhekka and Bürgi 2012). Additionally, the amide II band at 1673 cm−1 in the BSCZG0 sample shifts to 1645 cm−1 (III) and 1621 cm−1 (IV) in BSCZG0.

Fig. 9
figure 9

Deconvoluted IR spectra of Amide I and Amide II bands of BSA adsorbed on BSCZG10-glass

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Table 4 Deconvoluted IR spectra in the range (1600–1780 cm−1) of Amide I and Amide II bands of BSA adsorbed of BSCZG-glasses
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In contrast, in BSCZG20-glass, the center of this peak shifts to a lower wavenumber, specifically at 1619 cm−1. The ratio of Amide I to Amide II on all sample surfaces increased with higher concentrations of Ga ions in the borosilicate glass matrix. This observation aligns with the widely accepted hypothesis that electromagnetic interactions are crucial in protein adsorption (Healy and Ducheyne 1992). Furthermore, the results of FTIR analysis after protein adsorption (as shown in Fig. 9 and Table 4) indicate the increase in hydroxyl groups (OH−) with the increase of Ga2O3 content. This, in turn, leads to enhanced interactions between Ga3+ ions and the prepared bio-glasses, resulting in more significant protein adsorption due to the interaction between the NH2 amino group of BSA and the OH−. Additionally, the FTIR data (as seen in Fig. 3 and Table 1) reveal an increase in non-bridging oxygen (NBOs) groups in the (BO3) range, suggesting that more addition of Ga2O3 produces more NBOs groups. This may indicate a tendency for the network structure of the prepared glasses to adopt more open configuration, which improves protein absorption (Healy and Ducheyne 1992).

3.7 Cell viability

MTT analyses were conducted on Vero cell lines to evaluate the cytotoxicity of the compounds, with varying concentrations of each compound. As depicted in Fig. 10a–e, following 48 h of incubation, the relative cell viability exhibited a range of responses, spanning from BSCZG5μg.ml−1 to BSCZG20 μg.ml−1.

Fig. 10
figure 10

The cell viability for BSCZG-glasses, a BSCZG0, b BSCZG5, c BSCZG10, d BSCZG15, e BSCZG20 and f the half- maximal inhibitory (IC50) with increasing Ga2O3 content

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Figure 10 demonstrates that the half-maximal inhibitory concentration (IC50) values nearly double, increasing from 11.27 to 23.84 μg ml−1 as the Ga2O3 content varies from 0 to 20 mol%. These IC50 results indicate the impact of gallium ions concentration in borosilicate glass on cell growth. Bioactive glasses release ions into the surrounding fluid, promoting biocompatibility by releasing ions such as Si4+ and Ca2+. This phenomenon has been established in previous studies (Zeimaran et al. 2016; Alcaide et al. 2010). Consequently, Ga-containing bioactive glass, which elicits cellular responses and enhances surface roughness, can achieve favorable cytocompatibility by releasing ions and surface modifications (Pourshahrestani et al. 2017).

Based on the results above, it can be inferred that the increase of gallium ions concentration leads to enhanced cellular compatibility.

4 Conclusion

Using the melt quenching technique, we prepared a novel bioactive glass system consisting of gallium calcium zinc borosilicate glasses. Comprehensive studies were conducted to investigate the prepared samples' structure, physical, optical, and biomedical properties. XRD analysis confirmed the amorphous nature of the as-prepared samples, and hydroxyapatite (HA) was verified after immersion in simulated body fluid (SBF) are observed from FTIR results. The addition of Ga2O3 from 0 to 20 mol% increased the formation of non-bridging oxygens (NBOs), as indicated by the FTIR data. Furthermore, with the increase of Ga2O3 content both molar volume and experimental density values increased, ranging from 24.66 to 29.58 cm3 mol−1 and 2.70 to 3.14 g cm−3, respectively. The optical band gap values decreased from 3.27 to 3.08 eV, while the optical band tail increased from 0.20 to 0.25 eV with increasing Ga2O3 content. These characteristics possies BSCZG glasses as optimal for optoelectronic applications. Interestingly, although the incorporation of Ga ions increased the number of NBOs in the glass matrix, it reduced the ability to transfer negative charges from the glass network to probe ions in the prepared glasses. Electronic polarizability, resulting from these materials, can enhance cell viability, as demonstrated by the sample with the highest Ga ions content exhibiting a higher rate of protein uptake compared to sample free of Ga ions. This electronic polarizability enables electronic and optical applications and enhances the samples capability to absorb proteins. Finally, our findings indicate that these novel Ga free, Ga-borosilicate glasses are promising for biomedical applications due to their favorable characteristics. However, further investigation into Ga-borosilicate activity in vivo is imperative for clinical utilization.