Introduction

Nanoliposomes are a smaller variant of liposomes, one of the most widely used encapsulation and controlled release systems [1,2,3,4]. To gain a better understanding of nanoliposomes, we must first comprehend the earlier technology that they are based on namely, liposomes [5,6,7]. Liposome is derived from two greek words, lipos (fat) and soma (body or structure) and refers to a structure in which an aqueous compartment is encased by a fatty envelope [8, 9]. A liposomes (sometimes called bilayer lipid vesicles) are excellent cell and biomembrane models [10, 11]. Because of their likeness to biological membranes [12], they are a perfect system for studying not only modern biomembranes [13, 14] but also the emergence, function and evolution of primitive cell membranes [15, 16]. These structures are also employed as carrier systems by the food, cosmetics, agricultural [17, 18] and pharmaceutical industries [19] for the protection [20] and transportation of various materials like medicines [21], nutraceuticals [22], insecticides [23] and genetic material [24, 25]. Liposomes are made up of one or more concentric or nonconcentric lipid and phospholipid bilayers and biodegradable substrates for biomarkers and in drug delivery [26,27,28], and they can also contain other molecules like proteins [29, 30]. They can be single or multilamellar in terms of the number of bilayers they contain [31], and their aqueous and/or lipid compartments can accept hydrophilic, lipophilic [32] and amphiphilic molecules[33]. Liposomes and nanoliposomes have similar chemical, structural and thermodynamic features in general; these structures with quantum dots can increase the speed of cell penetration and intra-tissue process with high efficiency [34]. Nanoliposomes, on the other hand, have a larger surface area than liposomes and hence have the potential to increase solubility [35], improve bioavailability [36], improve controlled release [37] and enable more precise targeting of the encapsulated material [38]. Quantum dots (QDs), as a group of semiconducting nanomaterials, have advantages for wide applications in biology, they are used as markers for specific cells such as luminescent probes [39], labeled cancer cells [40] and transplanted cells from host cells [41]. Nanoliposomes, also known as submicron bilayer lipid vesicles are a relatively new technology for encapsulating and delivering bioactive substances the use of QD luminescent labels has the potential to eliminate most of these problems [42]. Nanoliposomes have potential uses in a wide range of disciplines, including nanotherapy (e.g. diagnosis, cancer therapy, gene transfer), cosmetics [43], food technology [44], and agriculture [45], due to their biocompatibility and biodegradability [46], as well as their nanosize. QDs as semiconductor nanoparticles (e.g. CdSe, InP, InAs) with diameters in the range of 2 to 10 nm are spherical nanoparticles with a diameter of a few nanometers that are highly emissive [47]. They serve as a platform for a family of materials that can be used in light emitting diodes, photovoltaic cells, and biosensors. The synthesis of quantum dots has gotten a lot of interest in recent years because of its unique optical, chemical, and electrical features which can decrease the systemic side effects of anticancer drugs through effectively increasing the surface-to-volume ratio [10, 48]. Fluorescence labeling as a safe and high efficiency method used for tracing and measuring nanoliposomes in vivo study [49]. Liposomes have shown advantages as drug carriers but they are associated with problems related to physical stability such as aggregation, sedimentation and leakage on storage. In this study, by preparing nanoliposomes loaded with α-Al2O3 nanoparticles, in addition to increasing the stability of the liposomes unique optical properties for use in smart drug delivery and targeted treatment of cancer cells was inducing in these structures.

In this study nanoliposomes bilayer lipid vesicle as a new structure for the encapsulation and delivery of α-Al2O3 quantum dots agents for in vivo imaging study. The final nanoliposomes loaded with α-Al2O3 quantum dots nanoparticles were characterized with DLS, SEM, TEM, TGA, FT-IR and Uv-vis spectroscopy.

Experimental

Methods and Materials

All of the materials required to carry out this research project were without further purification. The crystallinity structure of Al2O3 quantum dots nanoparticles (QDNPs) investigated using of X-Ray Diffraction with specifications a Rigaku D-max C III, X-ray diffractometer using Ni-filtered Cu Ka radiation. Cholesterol and non-ionic surfactants (Span40, sorbitan monopalmitate ≤ 99.0%) were purchased from SRL Co, Italy. Al(NO3)3.9H2O (CAS No.7784-27-2, MW: 375.13 g/mol) and NaOH (Molar mass: 39.997 g/mol,  ≤ 99.0%) were purchased from Merck company. Morphological properties evaluated with scanning electron microscopy (SEM), Philips XL-30 ESEM, and the transmission electron microscope (TEM, JEM1200EX, JEOL). The Fourier-transform infrared spectroscopy (FT-IR) spectra evaluated with Shimadzu Varian 4300 spectrophotometer in KBr pellets in the range of 500–3500 cm−1. The size distribution estimated with Dynamic Light Scattering (DLS/measurement range 0.3 nm–10.0 microns/Malvern Panalytical GmbH—Herrenberg, Germany). UV-Vis diffuse reflectance spectroscopy analysis was carried out using Shimadzu UV-2600 spectrophotometer. Analysis of variance (ANOVA) was carried out using Design Expert 7.0.0 package (Stat-Ease, Inc., Minneapolis, MN, USA). For in vivo imaging study of QDNPs, the mice (Balb/c male Inbred rats purchased from Animal care center aged between 8 and 6 weeks) were feeded and raised according to the Institutional an Animal Care and Use Committee (IACUC) protocol. To investigate the optical properties in the living organism we injected 0.001 mg/mL nanoliposomes loaded with α-Al2O3 NPs to the right leg (Balb/c male).

Preparation of Nanoliposomes

For the preparation of the liposomal system, according to laboratory conditions, the method of watering a thin layer was selected [50]. In the first, 300 µL of surfactant (Span 40) and 76 µL Cholesterol was dissolved in 20 mL chloroform in a 150 mL round-bottomed flask in reflux system. Above solution was heated and stirred in a magnetic stirrer at 400 rpm and 45 °C for 2 h.

Then the material, under static conditions for 60–50 min, were deposited as thin solid layers in the bottom of the balloon. For hydration, dry the layer of PBS saline solution (saline buffered Phosphate) was used. For better hydration, thin solid layers in the bottom of the balloon were exposed under a hairdryer at 45 °C for 60 min. In the final the milky solution was placed in the sonicator bath for 45 min at 60 watts. The nanoliposomes were collected in a falcon tube for characterization and the next step.

Nanoliposomes Loaded with α-Al2O3 NPs

At the first, 0.05 g of Al(NO3)3.9H2O in 10 mL propylene glycol was added. Then 3 mL NaOH 2 M was added drop by drop to the above solution under 400 rpm for 30 min to get a homogeneous mixture. For the preparation of nanoliposomes loaded with α-Al2O3 NPs, 2 mL of the white α-Al2O3 solution was added to 5 mL of nanoliposomes put into Teflon, and reaction was performed under microwave irradiation system at the various power and time. In this study, in order to design experiments, microwave irradiation and power were considered as variables and size were analyzed as a response.

Results and Discussion

Characterization

The results obtained from scanning electron microscopy (SEM) analysis show that the nanoliposomes based on lipid bilayers have been created as a carrier with suitable capacity for α-Al2O3 NPs. Figure 1A shows SEM images of the as synthesized nanoliposomes loaded with α-Al2O3 NPs in different concentrations such as 0.01 mg/mL (1a), 0.1 mg/mL (1b), 0.05 mg/mL (1c), 0.5 mg/mL (1d), 0.09 mg/mL (1e) and 0.9 mg/mL (1f) respectively. The new contract from as synthesized the α-Al2O3 NPs indicated a uniform substrate with the ability of connect to the nanoliposomes [51]. The relationship between concentrations of the α-Al2O3 NPs and the shape of the final formulation shows as the concentration of the α-Al2O3 NPs in the nanoliposomes as carriers, increases the adhesion of the structure increases significantly. This adhesion in the final formulation can be due to the increase in the surface-to-volume ratio of nanoparticles. The presence of porous holes in quantum dots is evident due to electron transfer cavity electron transfermate [52]. The PSA diagram of α-Al2O3 NPs is shown in Fig. 1B

Fig. 1
figure 1

A SEM images of the as synthesized nanoliposomes loaded with α-Al2O3 NPs in different concentrations such as 0.01 mg/mL (a), 0.1 mg/mL (b), 0.05 mg/mL (c), 0.5 mg/mL 1d, 0.09 mg/mL 1e and 0.9 mg/mL 1f respectively. The PSA diagram of α-Al2O3 NPs (B)

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To show the internal image of the nanoliposomes loaded with α-Al2O3 NPs we used transmission electron microscopy (TEM) analysis. The TEM image of the nanoliposomes loaded with α-Al2O3 NPs is shown in Fig. 2a. As the results show, two components including enclosed space and trapped nanoparticles can be easily detected. The core zone related to nanoliposomes which are dark borderline, is clearly visible. The α-Al2O3 NPs trapped in nanoliposomes as separate points are visible and the average particle size is estimated between 95 and 120. Figure 2b confirms the α-Al2O3 NPs particle size according to dynamic light scattering (DLS) analysis. The results show that the distribution number (Dn) in 10%: 11.17 nm, Dn 50%: 14.75 nm and Dn 90%: 20.38 nm. The particle size curve has a uniform distribution. The diffusion coefficient for the calculation of particle size distribution is obtained from the below relation:

$$\Gamma = {\text{D}}_{{\text{t}}} {\text{q}}^{{2}}$$
(1)

where q is the scattering vector, given by q = (4πn/λ). sin(θ/2). The refractive index of the solution is n. The wavelength of the laser light is λ, and the scattering angle is introduced with θ. Inserting Dt into the Stokes–Einstein equation according to Eq. 2 [53], solving for particle size is the final step.

$$D_{h} = \, k_{B} T/3\Pi \eta Dt$$
(2)
Fig. 2
figure 2

a The TEM image of the nanoliposomes loaded with α-Al2O3 NPs (a) and DLS diagram of α-Al2O3 NPs

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Dh, Dt are the hydrodynamic diameter and the translational diffusion coefficient. Also kB, T and η are Boltzmann’s constant, thermodynamic temperature and dynamic viscosity respectively.

In Fig. 3a, the Fourier transform infrared spectroscopy (FT-IR) is used for the investigation of the functional groups. The nanoliposomes as synthesized show the principal bands at about 2985 cm−1 and 2924 cm−1 which can be related to CH2 stretching groups in the span and cholesterol chains.

Fig. 3
figure 3

The FT-IR spectrum (a) and TGA/DTA profile of the nanoliposomes loaded with α-Al2O3 NPs (b)

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In addition, the absorption band centered at 1741 cm−1 is assigned to C = O stretching in the nanoliposomes loaded with α-Al2O3 NPs. The band centered at 1631 cm−1 correspond to symmetric vibrations CH2 groups in the final products. The band at about 1420 cm−1 is related to C–O–C groups in nanoliposomes. The band at about 1649 cm−1 and 950 cm−1 correspond with Al-O vibration in α-Al2O3 NPs. Connection points α-Al2O3 quantum dots nanoparticles to liposome structures occur through C-H bands. This can lead to the fabrication a new type of QDs with liposomes.

In this study thermos gravimetric analysis (TGA) technique used for physical and chemical characterization [54]. The first weight loss until about 130 °C is related to loss of adsorbed water from nanoliposomes loaded with α-Al2O3 NPs. The second mass loss can be related to the decomposition of the final products which happens in the range of 130 °C up to 150 °C which confirms that carbon chains between structures are broken. In this range carbon chains are broken in nanoliposomes as a carrier. After 150 °C up to 300 °C structural network at α-Al2O3 NPs is completely separated from each other and thermal degradation occurs. The differential thermal analysis (DTA) shows two endothermic transformations. The first strong peak occurs in the range of 130 °C up to 150 °C which can be related to phase transitions and the second occurs between 230 °C up to 240 °C due to melting points. TGA/DTA curves of nanoliposomes loaded with α-Al2O3 NPs are shown in Fig. 3b.

Statistical Analyses

According to the analysis of variance (ANOVA) experiments were performed regarding one replicate and three center points (23–1). The effects of the independent variables on the experimental design and obtained the final equation in terms of coded factors are represented in Table 1.

Table 1 Coefficient estimate and confidence limit low and high in the suggested model
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The mathematical relationship between the three factors was estimated by the two-factor interaction model equation.

$${\text{R}} = + {17}.{25} + {4}.{\text{25 A}} - {3}.{\text{75 B}} + {4}.{\text{25 BC}} + {2}.{\text{75 ABC}}$$
(3)

R is the predicted response (size), A, B and C represent the coded levels of the independent variables such as power, time and concentration in the statistical model. According to the ANOVA results, the model of the proposed study was significant (p ≤ 0.0001) while the lack of fit of the model was not significant (p ≥ 0.9502). The difference between Adj R-squared (0.7627) and pred R-squared (0.7601) is estimated at about 0.0026, which shows that the model argument is very accurate.

Figure 4a, b and c show three-dimensional (3D) contour plots, the effects of the α-Al2O3 quantum dots nanoparticles concentration, irradiation time and microwave power on the final size of nanoliposomes loaded with α-Al2O3 quantum dots nanoparticles. The minimum nanoparticles size in this study was achieved at the highest irradiation time (15 min) and the lowest microwave power (180 watts) and α-Al2O3 concentration (0.05 g).

Fig. 4
figure 4

Three-dimensional (3D) contour plots, the effects of Vconcentration (A), microwave power (B) and irradiation time (C) on the final size of nanoliposomes loaded with α-Al2O3 quantum dots nanoparticles

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Therefore, according to the suggested model, the Pred R2 is in reasonable agreement with the Adj R2 which shows that there is an excellent correlation between the predicted values and the experimental results (R2 = 0.9941). Figure 5a and b show desirability and predicted vs. actual in statistical analyses. The results show that the effect of the variables irradiation time and microwave power on the particle size response of the final products are very significant compared to α-Al2O3 concentration. According to the model calculations, the best size (8.41 nm) with the highest desirability can be obtained at microwave power (180.29 watts), irradiation time (14.99 min) and α-Al2O3 concentration (0.06 g).

Fig. 5
figure 5

Desirability diagram (a) and predicted vs. actual (b) in statistical analyses

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Table 2 shows that the model of the study is significant, while the lack of fit of the model was not significant (p ≥ 0.9502). The Model F-value of 8.23 implies the model is significant. There is only a 2.00% chance that a "Model F-Value" this large could occur due to noise. The "Curvature F-value" of 22.70 implies there is significant curvature (as measured by the difference between the average of the center points and the average of the factorial points) in the design space. There is only a 0.50% chance that a "Curvature F-value" this large could occur due to noise.

Table 2 Analysis of variance (ANOVA) of medium components related to size response as per two-level factorial design
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Optical Properties and in vivo Study

For the investigation of the optical properties of nanoliposomes loaded with α-Al2O3 NPs we used UV-Vis absorption spectroscopy in room temperature. In Fig. 6a, the absorption spectra show a strong peak in the wavenumber of about 225 nm. This is blue shift relative to the empty liposomes as potential vehicles [55]. The UV-Vis absorption spectroscopy data shows well that the presence of α-Al2O3 NPs has created unique optical properties for in vivo imaging [56, 57]. The results show a good light reflection in nanoliposomes loaded with α-Al2O3 NPs compared to the blank sample and the liposomes sample only. The nanoliposomes loaded with α-Al2O3 NPs have been highly efficient in vivo research due to the distance between the conduction levels and capacitance levels through appropriate light emission [58]. To investigate the optical properties in the living organism we injected 0.001 mg/mL nanoliposomes loaded with α-Al2O3 NPs to the right leg (Balb/c male). Then a 1:2 ratios of ketamine/xylazine was injected for anesthesia immediately. After 3 min, the optical properties of nanoliposomes loaded with α-Al2O3 NPs is clearly visible on the right leg. How to inject into mice and in vivo image of mice after 3 min are illustrated in Fig. 6b and c respectively. The bright spots indicate α-Al2O3 quantum dots nanoparticles with high luminescence activity due to the quantum effect. The existence of the quantum dot structure gives a significant synergistic effect in image formation at in vivo imaging studies. The bright white spots are characteristic α-Al2O3 quantum dots nanoparticles and this can be due to the unique properties through a high surface-to-volume ratio from these structures. This shows that quantum dots nanoparticles absorb more amount drugs on their surface.

Fig. 6
figure 6

The UV spectrum of the nanoliposomes loaded with α-Al2O3 quantum dots nanoparticles (a) and inject into mice (b) and in vivo image of mice 3 min after of injection (c)

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X-ray diffraction technique in room temperature of α-Al2O3 quantum dots nanoparticles is indicating in Fig. 7. The presence of peaks with the same position peaks of XRD patterns of Al2O3 nanoparticles show crystal phase have been formed. The X-ray diffraction measured in the range of 10 < 2Ө < 80. The X-ray diffraction analysis indexed as 27.1° and 38.8° could be have in positions as (121), (211). The crystallographic parameters for Al2O3 were a = 4.7606 A°, b = 4.7606 A°, c = 12.9940 A° and crystal system was rhombohedral.

Fig. 7
figure 7

X-ray diffraction patterns of α-Al2O3 quantum dots nanoparticles

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Conclusion

The nanoliposomes, as bilayer lipid vesicles, have the ability to encapsulate hydrophilic and hydrophobic drugs. In this study these nano-systems loaded with α-Al2O3 quantum dots nanoparticles as targeted tracking drug delivery carriers. According to the ANOVA results designed by 2 k factorial, the model was significant (p ≤ 0.0001) and the minimum size for nanoliposomes loaded with α-Al2O3 quantum dots nanoparticles was achieved at the highest irradiation time (15 min), the lowest microwave power (180 W) and α-Al2O3 concentration (0.05 g). The final products were characterized with DLS, SEM, TEM, TGA, FT-IR and UV-vis spectroscopy. In vivo study results show nanoliposomes loaded with α-Al2O3 quantum dots nanoparticles have good potential for creating optical properties in targeted drug delivery carriers.