1 Introduction

Cancer is a global problem that threatens human life and is one of the main causes of death in recent times [1]. Because conventional cancer therapies like chemotherapy and radiation damage both healthy and cancerous cells equally, they are no longer effective [2]. Particularly, cancer patients suffer from side effects, especially infection. Failure of an antibiotic raises the probability of death in cancer patients or those undergoing cancer therapies [3]. The crucial element of in vitro biological evaluation research is cytotoxicity. Studies on cytotoxicity are a helpful first step in identifying a substance’s potential harm to cells. The term “cell cytotoxicity” describes a substance’s or cell’s capacity to kill living organisms. Cell viability and- proliferation rates are reliable measures of a cell’s health [4]. Breast cancer is the most prevalent type of cancer among women worldwide cancer. The primary clinical treatment currently is surgery, which carries several risks of failure. Chemotherapy is costly and results in treatment failure if breast cancer cells (BCC) become multi-drug resistant (MDR) [5]. In addition, hepatocellular carcinoma (HCC) is a common type of cancer. There are numerous ways to treat HCC, yet its survival rate is still low. Although surgical resection and liver transplantation are effective treatments for HCC in its early stages, the majority of cases are not identified until the late stages [6, 7].

Polyurethane foam (PUF) is a low-cost material with a large surface area that works well as a substrate for cell adhesion and drug administration [8]. This class of polymeric materials was used in several industrial applications including furniture, coatings, paints, and fabrics in addition to their medical uses [9, 10]. PUF has more advantages than other polymers such as being lightweight, low-density, available, and bio-renewable resources [11, 12]. On the other hand, many microbes could contaminate the PUF surface, which shortens the validity period of its use and makes it harmful to human health [9, 13]. Moreover, PUF is primarily used as insulation; it needs to be resistant to microbes including bacteria, fungi, and viruses [14,15,16]. Therefore, several studies demonstrated the design of antimicrobial PUF by reduction of its microbial action by incorporation of N-halamine [17], silver nanoparticles [18, 19], and sub-nanometer [13] to enhance PUF antimicrobial activity.

Nanoparticles (NPs) have gained attraction for scientists due to their broad applicability in various fields, such as drug delivery, biomedicine, material science, biosensors and imaging [20, 21]. Various nanoparticles have been proved its applicability as anticancer drugs in tumor therapy [22]. Because of the nano-size, NPs have a high surface area to volume ratio, allowing for greater surface contact, higher reactivity, higher biological properties, and solubility [23]. Different nanoparticles (NPs) such as Ag, Au, Zn and Se were synthesized and developed as safe and effective alternative antimicrobial and anticancer agents [24]. For many industrial applications, metal and metal oxide NPs have gained great attention and are used extensively [25]. The green synthesized silver nanoparticles (AgNPs) using Penicillium brasilianum NP5 show significant antimicrobial activity and reduced cell proliferation in MDA-MB-231 breast cancer cells [26]. Also, Plumeria alba plant extract AgNPs demonstrated significant antimicrobial activity against bacteria and fungi, along with cytotoxic effects on the GBM U118 MG cancer cell line by inducing apoptosis [27]. Gold nanoparticles (Au NPs) exhibited heightened antibacterial effects against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus) at lower concentrations [28].

Currently, zinc and zinc oxide (ZnO) are used in many aspects of daily life, such as cosmetics, drugs, and skin-care products like sunscreens (for UV light scattering), hospital antibacterial paints, dental sealants, orthopedic reinforcing materials, cellular imaging, drug-delivery systems, and medical tools [29,30,31,32]. The antimicrobial properties of ZnO and zinc oxide nanoparticles (ZnONPs) are one of the primary reasons for using them as food packaging materials. Additionally, ZnONPs enable the advancement of packaging characteristics like stability, mechanical strength, and barrier qualities [33]. On the other hand, with the rise in antibiotic resistance, interest in nanomaterials with antibacterial characteristics is flourishing. ZnONPs as a nanomaterial, act as an antibacterial agent without any toxic side effects [34]. Also, ZnONPs were found to have promising anticancer activity owing to their distinctive features, which include biocompatibility, high selectivity, improved cytotoxicity, photo-catalytic agents, photo-oxidizing properties, and ease of manufacturing [35]. ZnONPs have demonstrated preferential toxicity against malignant cells through their distinct capacity to produce oxidative stress action in cancer cells, resulting in increased cancer cell cytotoxicity [32, 36]. Zn and ZnONPs were reported as strong antibacterial agents against both gram-positive (G+ve), gram-negative (G−ve) bacteria and fungi [37]. They also initiate the production of reactive oxygen species (ROS) during the interaction with bacteria or cells, leading to cell death [38, 39].

Nanocomposites (NCs) are materials comprising polymers as continuous phase besides NPs as discontinuous phase. NCs have gained a lot of interest owing to their various advantages for example flexibility, lightweight, ease of preparation, eco-friendliness, and affordability [40]. NCs were exploited for several biotechnological and biomedical uses such as wound healing, therapeutic delivery, medical devices, and burn dressing [41, 42]. The antimicrobial NCs were commonly exploited in coating and packaging applications of food to increase the shelf life of food products and prevent microbial proliferation [43]. NPs and NCs also act as drug-delivery systems that can conjugate different ligands or compounds and target other molecules [44]. With this great efficacy and selective targeting capabilities, NPs and NCs are starting to take precedence over more established cancer therapies like chemotherapy, radiation, and surgery in current cancer therapy [40].

The production of numerous physiologically active chemicals has recently attracted a lot of attention thanks to thiourea derivatives [SC(NH2)2] [45]. Drug research places a lot of emphasis on SC(NH2)2 derivatives containing nitrogen as well as sulfur atoms. Additionally, SC(NH2)2-derived compounds have demonstrated fungicidal and bactericidal properties [46]. Similar to this, SC(NH2)2 derivatives have demonstrated encouraging cytotoxic action against different types of tumors, such as liver and breast cancer [47].

The current work aimed to prepare and study the anticancer and antimicrobial properties of TPUF/ZnO, TPUF/ZnO was evaluated for its in vitro cytotoxic action via the MTT test against breast (MCF-7) and liver (HepG-2) cancer cell lines. In addition, the antimicrobial action of TPUF/ZnO was evaluated against E. coli, Bacillus cereus and Aspergillus niger.

2 Material and methods

2.1 Material and reagents

  • TPUF/ZnO: commercial flexible PUF (d = 12 kg/m3) was purchased from Foamex Company for foam production (Egypt). All chemicals used in the experiments were purchased from Sigma-Aldrich, Oxoid, and PioChem (Egypt).

  • Reference microbial strains: American type culture collection (ATCC) bacterial strains including E. coli (ATCC25922), B. cereus (ATCC9634), and fungal strain; A. niger (van Tieghem 1867) were sub-cultured on nutrient agar, nutrient broth, and Dox agar (Oxoid, UK) for bacteria and fungus, respectively. Penicillin (standard antibacterial), and Fluconazole (standard antifungal) were purchased from Pfizer Co., Ltd.

  • Cell lines human MCF-7, human HepG-2, and healthy cell line mammalian cells from African Green Monkey Kidney (Vero) were obtained from the American type culture collection ATCC (Rockville, MD, USA). MTT assay, trypan blue dye and Dimethyl sulfoxide (DMSO) were purchased from Sigma (USA). Fetal bovine serum, RPMI-1640, HEPES buffer solution, l-glutamine, gentamycin and 0.25% trypsin–EDTA were purchased from Lonza (Belgium).

2.2 Instruments

FTIR spectroscopy was employed using a JASCO FTIR-410 spectrometer (Germany). A JASCO UV/VIS Spectrometer v-630 (Japan) was used for all UV/Vis absorbance measurements. A JEOL JEM-2100 (Japan) transmission electron microscope (TEM) was used to study the ultrastructure of bacteria. The microplate reader (SunRise, TECAN, Inc., USA) assessed optical density (O.D.).

2.3 Preparation of TPUF/ZnO

  • ZnONPs: direct precipitation method by Cao et al., was used to prepare ZnO nanoparticles (ZnONPs). In this method, ZnSO4·7H2O was reacted with NaHCO3 and NH4OH solution at 60 °C for 30 min and a stable colloid was formed. The colloid was filtrated, washed, dried at 100 °C, and calcined at 400 °C for two hours [48]. ZnONPs was formed with its characteristic white color.

  • TPUF: PUF cubes weighing 10 g were submerged in HCl for two hours at 60 °C, cooled, and then rinsed with distilled water. PUF cubes were soaked in conc HCl and NH4SCN was added dropwise [49]. TPUF was formed with yellow color.

  • TPUF/ZnO: TPUF was refluxed with ZnONPs in ethanol for 2 h, then the product was washed and dried. TPUF/ZnO was formed with pale yellow color.

2.4 Characterization of TPUF/ZnO

  • UV–visible spectroscopic analysis: at the wavelength range of 200–500 nm, UV/Vis spectra of TPUF/ZnO, TPU, and ZnONPs in water were obtained.

  • FT-IR analysis: to pinpoint the precise functional groups, KBr disc (KBr pellet) was used to carry out infrared (IR) spectra in the 4000–400 cm−1 region.

  • XRD analysis: Brucker-D8 X-ray diffractometer (USA) equipped with Cu Kα radiation (λ = 1.54 Å) at a generator of 40 kV voltage and 40 mA current was used for phase identification. TPUF/ZnO was scanned using Bragg’s configuration for the 2θ range of 10°–80° with 0.03° S−1 scanning rate. XRD data was performed in the faculty of agriculture, Mansoura University. The particle size (D) of TPUF/ZnO was calculated using the Debye–Scherrer equation; \(\left( {D = K \lambda /\beta \cos \uptheta } \right)\). Where θ is the Bragg diffraction angle, K is the shape factor (0.97) for spherical particles, λ is the X-ray wavelength (0.15418 nm) and β is the peak full width at half maximum (FWHM) in radians.

  • Zeta potential and dynamic light scattering (DLS) analysis: zetasizer Nano-ZS (Malvern) were used to perform zeta potential and particle size disruption. TPUF/ZnO was dispersed in water and data was measured three times at room temperature.

  • Band gap energy (Eg): from the data of UV–Vis measurements, the band gap energy of TPUF/ZnO, TPU, and ZnONPs were determined using Tauc equation. For a direct bandgap semiconductor like ZnO [50]. The formula used is \(\left( {{\alpha h}\upupsilon } \right)^{2} = {\text{C }}\left( {{\text{Eg}} - {\text{h}}\upupsilon } \right)\). Where C is a constant. α is the absorption coefficient (\({\upalpha } = 2.303{\text{ A}}/{\text{t}}\)), A is the absorbance and t is the thickness. The energy hʋ (in eV) were calculated (\({\text{h}}\upupsilon = 1240/{\lambda }\)), where λ is the wavelength in nm. The (αhʋ)2 were plotted against hʋ and the energy gap can be approximated from the straight portion of the hʋ axis at hʋ = 0.

  • Boehm’s titration: the total acidic and basic groups of TPUF/ZnO were determined using Boehm’s titration, TPUF/ZnO was soaked in NaHCO3, Na2CO3, NaOH and HCl (0.05 M) and after 24 h, the solutions were titrated against HCl and NaOH (0.05 M).

  • The pH of zero point charge (pHPZC): the surface charge of TPUF/ZnO were evaluated over initial pH range of 2–14 and after 24 h, the final pH was measured using with a Jenway 3510, UK pH-meter.

  • Magnetic susceptibility \(\left( {{\upchi }_{{\text{g}}} } \right)\): from the data of the Evans balance, the magnetic susceptibility of TPUF/ZnO and TPU was estimated using the following equation: \({\upchi }_{{\text{g}}} = {\text{CL }}\left( {{\text{R}} - {\text{R}}_{0} } \right)/10^{9} \left( {{\text{M}} - {\text{M}}_{0} } \right)\). Where: balance calibration constant (1.35 cm); C, sample height in cm; L, balance reading for the sample in a tube; R, balance reading for the empty tube; Ro, mass of sample in gm; M and mass of empty tube in gm; M0.

  • Optical density (O.D.): the microplate reader (SunRise, TECAN, Inc., USA) was used to assess optical density.

2.5 Antimicrobial activity evaluation using agar well-diffusion method

The Antimicrobial activity of TPUF/ZnO against the G-ve bacterium; E. coli, G + ve bacterium B. cereus and fungus; A. niger was investigated according to the guidelines of the Laboratory Standards Methods [51]. In brief, the culture media (Nutrient agar and Dox agar) were prepared, autoclaved (121 °C, 15 min), and coaled at 47 °C. About 0.5 McFarland standards (1–2 × 108 CFU/mL) of the microbial cultures of E. coli, B. cereus, and A. niger were prepared. Next, the agar media were inoculated specifically with 100 μL of each microbial culture and poured into sterile petri dishes in triplicate. After solidification, small wells (5 mm) were punched using a sterile corkborer. Following this, 300 μg/mL of TPUF/ZnO, Penicillin (antibacterial) and Fluconazole (antifungal) in DMF were added into the wells separately. The inoculated nutrient agar plates were incubated at 37 °C for 24 h, and Dox agar plates were incubated at 30 °C for 5 days. After incubation time, zones of inhibition (ZOI) were measured in millimeters (mm).

2.6 Minimum inhibition concentration (MIC) Assay

The MIC of TPUF/ZnO against G+ve bacterium B. cereus, and G−ve bacterium; E. coli was studied. Nutrient broth was prepared, autoclaved (121 °C, 15 min), and coaled at 47 °C. The culture broths were inoculated with 100 μL of B. cereus and E. coli (0.5 McFarland standards (1–2 × 108 CFU/mL)) in two sets of flasks [52,53,54,55]. Aliquots 0–1000 μg/mL of TPUF/ZnO were prepared and placed into the flasks. In addition, flasks were used as a positive control (without TPUF/ZnO) and a negative control (DMF) for each strain. The flasks were incubated in a shaker incubator (100 rpm) at 30 °C for 24 h. The MIC value was recorded by measuring the microbial growth spectrophotometrically (λ = 600 nm). The growth inhibition percentage was calculated using the following formula:

$${\text{Growth inhibition \% }} = \left[ {\left( {OD_{C} - OD_{t} } \right)/OD_{C} } \right] \times 100$$

where ODc is the O.D. of the control (without TPUF/ZnO); and ODt is the O.D. of tested TPUF/ZnO.

2.7 Ultrastructure study of the TPUF/ZnO-treated bacteria

The ultrastructure of TPUF/ZnO-treated B. cereus and E. coli bacteria (MIC values), and the untreated bacteria were examined using TEM [56]. The bacterial cells were fixed with 2.5% glutaraldehyde and 0.1 M cacodylate buffer, pH 7, after being spun at 5000 rpm for 15 min. The samples were prepared, cut into cross sections with an ultra-microtome (50 µm), and then put onto copper grids (Type G-200, 3.05 μM diameter, TAAP, USA) that had been coated with carbon. The samples were photographed using a TEM running at a 200 kV accelerating voltage.

2.8 Analysis of anticancer activity

The viability of MCF-7 breast cancer cells, HepG-2 hepatocellular carcinoma, and Vero cells treated with TPUF/ZnO was assessed using dimethylthiazol-diphenyltetrazolium bromide (MTT) and measured using a UV-spectrophotometer as described by Venugopal et al. [57]. Initially, an RPMI-1640 medium was prepared following standard procedures to create a complete medium, and the required amount was dispensed into a 96-well plate. Subsequently, 5 × 104 cells/well of breast cancer cells were diluted and cultured under 5% CO2 conditions with a 95% humidity range. Different concentrations ranging (5–100 µg/mL) from TPUF/ZnO were added to the wells in increasing order, and the cells were then incubated.

Positive controls included RPMI-1640 alone plus MCF-7 and HepG-2 cells, while negative controls consisted of MCF-7 or HepG-2 cells plus dimethyl sulfoxide (DMSO). MTT solution was added to all wells and covered with aluminum foil, leading to the formation of formazan crystals inside the wells. The interactions between TPUF/ZnO and MCF-7 breast cancer cells or HepG-2 hepatocellular carcinoma were confirmed by calculating the color intensity formed at 540 nm using a UV-spectrometer [58]. The results were obtained in triplicate, and cell viability was determined by the following calculation.

$${\text{Viability \% }} = \left( {OD_{t} /OD_{c} } \right) \times 100\%$$

where the mean O.D. of cells treated with TPUF/ZnO; ODt and the mean O.D. of untreated cells; ODc, and the results were expressed as the mean ± standard error of the mean. The relation between surviving cells and drug concentration is plotted to get the survival curve of each cancer cell line after treatment with TPUF/ZnO.

The 50% inhibitory concentration (IC50), the concentration required to cause toxic effects in 50% of intact cells, was estimated from graphic plots of the dose–response curve for each concentration. The half-maximal effective concentration (EC50), the concentration of TPUF/ZnO that gives a half-maximal response was also estimated.

In the calculation, untreated wells, lacking TPUF/ZnO, served as unaffected controls with 100% viability. Treated results were then compared to the control results to detect viability in the 96-well plate. Ultimately, the concentration of the well resulting in 50% viability was established as the IC50 concentration. GraphPad Prism software (San Diego, USA) was used to calculate the percentage of cell viability and to derive IC50 values. Data are presented as the mean ± standard deviation (S.D). IC50 was estimated using GraphPad Prism 6 software (GraphPad Software, San Diego, CA). EC50 (effective concentrations) was using the Quest Graph IC50 Calculator.

$${\text{\% IC}}_{{{50}}} = \left( {OD_{c} - OD_{t} } \right) \times 100\%$$

where the mean O.D. of cells treated with TPUF/ZnO; ODt and the mean O.D. of untreated cells; Odc, and the results were expressed as the mean ± standard error of the mean.

2.9 Statistical analysis

Using SPSS software version 18 and the ANOVA test, the results were tested. The threshold for significance was set at 0.05. Duncan’s multiple range test was done to determine the intergroup comparison. Three different experiments were run. Every result was shown together with its mean and standard error (S.E.).

3 Results

3.1 Characterization of TPUF/ZnO

  • UV–visible spectroscopic analysis: UV/Vis spectra of TPUF/ZnO, TPU, and ZnONPs were recorded in the range of 200–500 nm (Fig. 1). It was revealed that TPUF/ZnO and ZnONPs absorbed UV radiation at 351 nm, confirming the nanoparticle size.

  • FT-IR analysis: FTIR spectra of TPUF/ZnO, TPU and ZnONPs were recorded in the range of 400 and 4000 cm−1 (Fig. 2). The characteristic peaks of Zn–O were observed at 833, 603 and 447 cm−1; while broadband was observed from 3720 to 2720 cm–1 was assigned OH groups. Several peaks were observed at 2900 (C–H), 2080 (N=C=S), 1629 (C=O), 1513 (C–O–C) and 1100 cm−1 (C–O), which were assigned to TPU. The observed broad bands at 3670–3276 and 3270–3207 cm–1; were assigned to the NH and OH groups. The new characteristic band appeared at 875–400 cm−1, resulting from the coupling of TPU matrix and ZnONPs.

  • XRD analysis: the XRD patterns of TPUF/ZnO showed strong and narrow diffraction peaks (Fig. 3), which refers to the good crystallinity of TPUF/ZnO. The characteristic diffraction patterns of TPUF/ZnO appeared at 2Ɵ = 31.9, 34.5, 36.4, 47.6, 56.8, 63.0, 68.3, 69.1 and 76.9°; these correspond to crystal planes of (100), (002), (101), (102), (110), (103), (200), (112) and (201). The diffraction peaks at 31.9 (100), 34.5 (002), 36.4 (101), 47.6 (102), 56.8 (110) and 63.0 (103) were attributed to the hexagonal wurtzite phase of ZnONPs. However, the diffraction peaks at 2θ around 68.3 (200), 69.1 (112) and 76.9◦ (201) indicate the coupling between TPUF and ZnONPs. The TPUF/ZnO X-ray patterns exhibit a hexagonal wurtizite crystal system (space group P63mc). The order of their lattice parameters is as follows: (a = b = 0.325 nm, c = 0.521 nm and α = β = 90°, γ = 120°). The results showed that modification of TPU with ZnONPs caused a phase change in the crystal structure. The particle size (D) of TPUF/ZnO was calculated using the Debye–Scherrer equation, and the average crystallite size of TPUF/ZnO was 18.4 nm.

  • Zeta potential and dynamic light scattering (DLS) analysis: it was revealed that TPUF/ZnO were stable with a zeta potential value of − 12.87 ± 0.51 mv (Fig. 4A). It was stated that TPUF/ZnO were negatively charged on their surfaces. The particle size distribution of TPUF/ZnO varied from 582.4 to 772.6 nm (Fig. 5B). The mean diameter of the nanoparticles, according to DLS was found to be 677.2 ± 95.11 nm.

  • Band gap energy (Eg): the band gap energy of TPUF/ZnO, TPU, and ZnONPs was estimated as 2.8, 2.99, and 1.52 eV for a direct band gap semiconductor (Fig. 5). A lower energy gap of TPUF/ZnO than TPU refers to higher particle size [35], confirming the immobilization of ZnONPs onto TPU surfaces. This result will exhibit an increase in the surface polarity and electrical conductivity of TPUF/ZnO compared to TPU.

Fig. 1
figure 1

UV/Vis spectra for TPUF/ZnO, TPU and ZnONPs

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Fig. 2
figure 2

FTIR spectra for TPUF/ZnO, TPU and ZnONPs

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Fig. 3
figure 3

XRD of TPUF/ZnO

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Fig. 4
figure 4

Zeta potential; (A) and particles size distribution by intensity; (B), of TPUF/ZnO

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Fig. 5
figure 5

Band gap energy for TPUF/ZnO, TPU and ZnONPs

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The total acidic and basic sites of TPUF/ZnO and TPU were determined by Boehm’s titration. The total acidity of TPUF/ZnO (52 mmol/g) were higher than TPU (20 mmol/g), while basic sites were negligible. The surface charge of TPUF/ZnO and TPU was estimated over the pH range of 2–14 and pH at zero charge point (pHPZC) was found to be 5.5 and 4.1 (Fig. 6). The surface charge of the TPUF/ZnO composite will be negative at pH above 5.5 and positive at pH below 5.5. A higher pHPZC value exhibits a higher adsorption capacity of TPUF/ZnO towards negatively charged compounds.

  • The magnetic susceptibility of TPUF/ZnO was +0.82 × 10–7 cm3/mol, which is very low but positive. TPUF/ZnO was estimated as weakly magnetic and showed paramagnetic characteristics. The magnetic susceptibility of TPU was −3.24 × 10–7 cm3/mol, which was considered a diamagnetic material.

  • The chemical stability of TPUF/ZnO was confirmed in the presence of buffer solutions (pH: 2–14), and organic solvents (e.g., CH3OH, CH3COCH3, C6H6, C6H5CH3, DMF, and DMSO).

Fig. 6
figure 6

pHPZC for TPUF/ZnO and TPU

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3.2 Antimicrobial activity evaluation

The agar well diffusion test was applied to calculate the ZOI of TPUF/ZnO against G+ve B. cereus, G−ve E. coli and A. niger. TPUF/ZnO revealed a good antimicrobial action, as shown in Fig. 7 and Table 1.

Fig. 7
figure 7

Antimicrobial activity of TPUF/ZnO in comparison with Penicillin (standard antibacterial) and Fluconazole (standard antifungal) using agar well diffusion method against B. cereus, E. coli, and A. niger. Arrows denote the diameter of inhibition zones (mm)

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Table 1 Antimicrobial effect of TPUF/ZnO in comparison with penicillin (standard antibacterial) and fluconazole (standard antifungal)
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The MIC of TPUF/ZnO against B. cereus and E. coli was determined (Figs. 8, 9).

Fig. 8
figure 8

Minimum inhibition concentrations of TPUF/ZnO against B. cereus and E. coli

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Fig. 9
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Growth inhibition percentage of E. coli and B. cereus in the presence of different concentrations of TPUF/ZnO

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The antibacterial effects of TPUF/ZnO against B. cereus and E. coli were examined by TEM analysis, as shown in Fig. 10.

Fig. 10
figure 10

The bactericidal action of TPUF/ZnO on the ultrastructure of E. coli and B. cereus. TPUF/ZnO-treated bacteria appeared as malformed irregular rods (white arrows) with lysed cell walls (LY), the separation between the cell wall and plasma membrane (S), vacuole formation (V), and complete cell lysis (Cl). CW and CY refer to cell walls and cytoplasm, respectively

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3.3 Cytotoxic activity evaluation

TPUF/ZnO was evaluated for its cytotoxic effects against two human cancer cell line: MCF-7 and HepG-2. The cell viability curves over a concentration range of TPUF/ZnO after 24 h of treatment in MCF-7 and HepG-2 cells were estimated (Table 2, 3, 4, 5). According to the MTT cytotoxicity assay results, within the concentration range (0–500 μg/mL) used in the study, TPUF/ZnO showed good cytotoxic activity in cancer cell lines (Fig. 11). The concentration–response curves and the IC50 values were generated using the inhibitor-normalized response variable slope function in GraphPad Prism 7 software. IC50 values of TPUF/ZnO for HepG-2 and MCF-7 cells were found 77.08 ± 1.36 µg/mL and 109.01 ± 3.98 µg/mL, respectively. Comparable IC50 values of Cisplatin for HepG-2 and MCF-7 cells were found to be 3.58 ± 0.34 µg/mL and 5.72 ± 0.59 µg/mL, respectively (Table 4). These results showed a lower IC50 value of TPUF/ZnO for HepG-2 than comparable IC50 for MCF-7. TPUF/ZnO showed higher cytotoxic activity against HepG-2 than MCF-7 cells. Estimation the selectivity index of TPUF/ZnO is identified as the ratio between IC50 of TPUF/ZnO against normal cell line and cancer one. TPUF/ZnO showed values against MCF-7 and HepG-2 of 0.729 and 1.029, respectively; while Cisplatin showed values of 0.360 and 0.575 against MCF-7 and HepG-2, respectively.

Table 2 Inhibitory activity of TPUF/ZnO against breast carcinoma cells MCF-7
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Table 3 Inhibitory activity of TPUF/ZnO against hepatocellular carcinoma cells (HepG-2)
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Table 4 IC50 values and selectivity index of TPUF/ZnO and cisplatin in MCF-7 and HepG-2 cells (24 h of treatment)
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Table 5 EC50 values of TPUF/ZnO and cisplatin in MCF-7 and HepG-2 cells
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Fig. 11
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Cytotoxicity assessment of TPUF/ZnO and Cisplatin (reference drug) against MCF-7 and HepG-2 cells after 24 h of treatment

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The cell viability % data were administered with an AAT Bioquest EC50 Calculator (Sunnyvale, CA, USA) to obtain the concentration at which TPUF/ZnO exerts half of its maximum response values (EC50) towards HepG-2 and MCF-7 cells. EC50 values of TPU/ZnO and Cisplatin against MCF-7 was 100.44 and 6.31, respectively. While EC50 values of TPUF/ZnO and Cisplatin against HepG-2 was 69.89 and 4.80, respectively (Fig. 12).

Fig. 12
figure 12

Semi-log dose–response curves and calculated EC50 values of TPUF/ZnO in comparison to Cisplatin against MCF-7 and HepG-2 cells. Cell viability was determined using an MTT assay

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4 Discussion

Gram-positive, aerobic, spore-forming B. cereus is found in different habitats. B. cereus is one of the food pathogens that can cause epidemics of food poisoning that include vomiting or diarrhea. Because B. cereus is challenging to eradicate using conventional procedures and approaches, it poses a serious risk to food safety and public health [58]. A G−ve bacterium called E. coli typically dwells in’’people’s intestines. E. coli is a dangerous food-pathogenic bacterium that spoils food, which when consumed can lead to several life-threatening consequences. Constipation, diarrhea, exhaustion, fever, and vomiting are possible side effects [30]. One of the most popular fungi that can result in life-threatening infections is A. niger. The aerobic fungal microbe A. niger usually infects only immunocompromised people and on occasion acts as a pathogen. It can only produce mycotoxins under specific circumstances. [59].

TPUF/ZnO showed a higher antibacterial action against G−ve E. coli than G+ve B. cereus with ZOI’s of 16 and 13 mm, respectively. Penicillin showed a stronger antibacterial effect; with ZOI of 40 mm against E. coli, and 25 mm against B. cereus. According to Marzi et al. [60], SC(NH2)2 derivatives are effective antibacterial agents against B. cereus and E. coli, which produced ZOI of 11 and 9 mm, respectively. TPUF/ZnO displayed higher antifungal action against A. niger (26 mm) than the standard antifungal agent, Fluconazole (14 mm). Bacterial cell walls have a −ve charge due to the existence of acidic compounds such as peptidoglycan. G+ve bacteria (B. cereus) contain thicker layers of peptidoglycan than G−ve bacteria (E. coli) which increase their cell wall −ve charge value [61]. TPUF/ZnO −ve charge might produce a repulsion force between it and the bacterial cells, which might decrease its antibacterial effect compared to the standard antibacterial agent, Penicillin. In addition, this repulsion force increased in the case of G+ve bacteria (high −ve charge of peptidoglycan content) than in G−ve bacteria, which might decrease the antibacterial action against G+ve bacteria [62].

MIC is defined in vitro as the smallest concentration of TPUF/ZnO that will inhibit the visible growth of bacteria after overnight incubation. The antibacterial ratios of TPUF/ZnO against B. cereus and E. coli were 350 and 400 μg/mL (MIC value). The growth inhibition curve of B. cereus and E. coli in the presence of a series of concentrations of TPUF/ZnO was studied. Above these MIC values, dosages of TPUF/ZnO antibacterial ratios were attained by 100%, which confirmed the total killing of E. coli and B. cereus.

TEM micrographs were investigated to study the antibacterial action of TPUF/ZnO against B. cereus and E. coli. Untreated E. coli possessed intact cell walls, normal cytoplasm concentrations, and rod-like morphologies. E. coli cell walls showed signs of wrinkling, breakage, separation from the plasma membrane, and vacuole formation after the treatment by TPUF/ZnO, which caused cellular content to leave the cell. The control micrograph displayed serrate-shaped cell wall cells and a consistently dense and homogenous microstructure, indicating that the cells were intact. In contrast, the TPUF/ZnO-affected cells showed noticeable modifications in the contents of the bacterial cell, including dissociation of the cell wall from the cell membrane and lysed cell walls.

Other studies reported that the antimicrobial activity of ZnONPs might cause the generation of ROS and the loss of membrane integrity [63, 64]. The production of ROS can cause oxidative stress in bacterial cells, which inhibits DNA replication and protein synthesis. The cytoplasmic membrane’s charges can become unstable by ZnO electronic stimulation, which can lead to its rupture. ZnO can inhibit the glycolytic enzyme and harm the cytoplasmic membrane [65]. The peptides in the microbial cell wall that SC(NH2)2 could bind to strongly downregulated the metabolism of glucose, alanine, aspartic acid, glutamic acid, arginine, and proline. By destroying the enzymes necessary for these crucial steps connected to the growth of the microorganisms, this action may exhibit its antibacterial action [66].

The cytotoxic action of TPUF/ZnO was studied against MCF-7 and HepG-2 human cell lines. The MTT assay was performed to investigate the TPUF/ZnO effects on cell viability. IC50 value gives information related to the potency of a drug or substance in a pharmacology study [67]. Sebaugh et al. [68] stated that this value could become a benchmark for drug toxicity because the lower the IC50, the higher the toxicity effects. TPUF/ZnO showed a higher toxicity effect against HepG-2 than MCF-7 cell line, IC50 values are 77.08 ± 1.36 and 109.01 ± 3.98 respectively. As an antineoplastic agent, a high selective index (SI) is required to produce the maximum effect on cancer cells and then the effect on non-cancer healthy cells [69]. Inhibitory activity of TPUF/ZnO against Hepatocellular carcinoma cells HepG-2 was more active than against BCC, MCF-7. Our results are similar to Payolla et al. [70] who showed vanadium-based complexes which showed a higher selectivity index and better in vitro results than Cisplatin. Also, Chen et al. [71] supposed that the net percentage of HepG-2 cells captured by negatively charged NPs was higher than that of MCF-7 cells. Despite the IC50 value of TPUF/ZnO nanocomposite for both cancer cell lines being higher than Cisplatin’s value, TPUF/ZnO showed higher SI than Cisplatin. This means TPUF/ZnO is a safer and more selective anticancer material. Rajivgandhi et al. reported that the increase in Ag NPs concentration decreases cell viability [72]. These findings demonstrated that NPs act as a concentration-dependent anticancer agent against MCF-7 breast cancer cells. At a concentration of 10 µg/mL, Ag NPs initiated their inhibitory role in viability, progressing to 51% cell death at a concentration of 75 µg/mL. Complete deactivation of cancer cell survival rate was observed at a concentration of 150 µg/mL. Pyrrolo[1, 2-a]pyrazine-1, 4-dione, hexahydro-3] was successfully identified, and it is noteworthy for its remarkable anticancer activity against MCF-7 human breast cancer cells at a concentration of 250 µg/mL [73]. The confirmation of its anticancer potential was substantiated through morphological damages and intracellular damages observed in ROS and Hoechst 33, 342 stain. Another study showed that chitosan-loaded plant essential oils have excellent anti-bacterial and anticancer properties [74, 75]. While the anticancer effect of biosynthesized Caulerpa taxifolia Ag NPs exhibited excellent cytotoxicity against A549 lung cancer cells at 70 µg/mL concentration [76]. The cytotoxic efficacy of aaptamine against HepG 2 cells was shown at 75 µg/mL [77].

SC(NH2)2 derivatives are among the most promising anticancer agents. Many substituted SC(NH2)2 derivatives were confirmed to have significant cytotoxic activity against different cancer cell lines [78]. Their anticancer activity may be due to their ability to inhibit some enzymes such as protein tyrosine kinases (PTKs), topoisomerase II, human sirtuin-type proteins as well as DNA repair synthesis. Abbas et al. showed that many SC(NH2)2 derivatives have a higher cytotoxic activity towards HepG-2 than MCF-7 cancerous cell lines [79]. Moghaddam et al. [80] reported that ZnONPs exhibited inhibition against the proliferation of MCF-7 cancer cell lines, and the IC50 value was 121 µg/mL, after 24 h of treatment. Wang et al. [81] analyzed the anticancer activity of ZnONPs and the IC50 dose was 7.5 μg/ml for 24 h of treatment. These results are similar to our data in which the IC50 of HepG-2 cells was lower than that of MCF-7 cell lines.

5 Conclusion

TPUF/ZnO was synthesized by coupling ZnONPs with thiourea polyurethane foam. Several characterization criteria of TPUF/ZnO were performed and discussed, such as UV/Vis, IR, XRD, Zeta Potential, DLS Analyzes. Also bandgap energy, magnetic susceptibility, chemical stability, and pHPZC were investigated. TPUF/ZnO was tested for its anti-bacterial, antifungal, and anticancer activities. Human breast cancer cell line (MCF-7) and human liver cancer (HepG-2) were used to assess in vitro the anticancer activity of TPUF/ZnO using the MTT assay. TPUF/ZnO shows considerable concentration-dependent cytotoxic activity against MCF-7 and HepG-2 cells, and it is interesting to continue studies for in vivo applications. E. coli, B. cereus, and A. niger were used to study the in vitro antimicrobial activity of TPUF/ZnO. Successfully inhibiting the growth of tested microbial strains can be proven TPUF/ZnO as an as an effective antimicrobial agent.