Ky-Vien
Le
ab,
Hanh-Vy Tran
Nguyen
ab,
Phu-Quan
Pham
bc,
Ngoc Hong
Nguyen
bc,
Tan Le Hoang
Doan
ab,
Linh Ho Thuy
Nguyen
be,
Bach Thang
Phan
ab,
Lan Thi My
Nguyen
*bd,
Sungkyun
Park
f,
Ngoc Kim
Pham
*bc,
Philip Anggo
Krisbiantoro
g,
Kevin C.-W.
Wu
*ghi and
Ngoc Xuan Dat
Mai
*ab
aCenter for Innovative Materials and Architectures (INOMAR), Ho Chi Minh City, Vietnam. E-mail: mnxdat@inomar.edu.vn
bVietnam National University, Ho Chi Minh City, Vietnam
cFaculty of Materials Science and Technology, University of Science, Ho Chi Minh City, Vietnam
dFaculty of Biology and Biotechnology, University of Science, Ho Chi Minh City, Vietnam
eFaculty of Pharmacy, University of Health Sciences (UHS), Ho Chi Minh City, Vietnam
fDepartment of Physics, Pusan National University, Busan, South Korea
gDepartment of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan. E-mail: kevinwu@ntu.edu.tw
hDepartment of Chemical Engineering and Materials Science, Yuan Ze University, Chung-Li, Taoyuan, Taiwan
iInstitute of Biomedical Engineering and Nanomedicine, National Health Research Institute, Keyan Road, Zhunan, Miaoli City 350, Taiwan
First published on 25th March 2025
Hybrid materials possess the unique properties of their individual components, enabling their use in multiple synergistic applications. In this study, we synthesized biogenic fluorescent carbon dots (CDs) decorated with biodegradable periodic mesoporous organosilica nanoparticles (BPMO), creating BPMO@CDs. The CDs, approximately 9.8 nm in diameter, were derived from Musa paradisiaca cv. Awak juice using a rapid microwave method, exhibiting a spherical shape and green and red luminescence. The resulting BPMO@CDs are spherical, around 100 nm in size, and maintain high pore volume and surface area. The elemental chemical state in the BPMO@CDs remains consistent with that of pure BPMO. Our findings demonstrate that BPMO@CDs achieve efficient cellular uptake rates of 46.74% in MCF7 cells and 17.07% in L929 cells, with preserved fluorescence within the cells. The optical properties of the CDs are retained in the BPMO@CDs, allowing for detection upon cellular uptake. Additionally, when loaded with anticancer drugs, the BPMO@CDs significantly enhance the cytotoxicity against MCF7 breast cancer cells, highlighting their potential for synergistic bioimaging and chemotherapy applications.
New conceptsWe report the green synthesis of fluorescent carbon dots (CDs) from banana (Musa paradisiaca cv. Awak) juice using a rapid microwave technique. These CDs are subsequently incorporated into biodegradable periodic mesoporous organosilica nanoparticles (BPMO) via the sol–gel method to form hybrid nanomaterials, BPMO@CDs. The hybrid materials exhibit high porosity, strong luminescence, low cytotoxicity, increased loading capacity, and enhanced toxicity toward cancer cells, demonstrating their potential for biomedical applications. For instance, we demonstrate that BPMO@CDs achieve efficient cellular uptake in MCF7 and L929 cells, with preserved fluorescence within the cells. The optical properties of the CDs are retained in the BPMO@CDs, allowing for detection upon cellular uptake. Additionally, when loaded with anticancer drugs, BPMO@CDs significantly enhance the cytotoxicity against MCF7 breast cancer cells, highlighting their potential for synergistic bioimaging and chemotherapy applications. This study provides a new concept of using environmentally friendly, biocompatible hybrid nanomaterials with potential for biomedical applications, particularly in bioimaging and drug delivery. |
Among the mentioned materials, mesoporous silica nanoparticles (MSNs), with their prominent characteristics such as high surface area, porous structure, and biocompatibility, by and large, have garnered attention. Nevertheless, MSNs, being inherently inorganic and difficult to degrade, are still assumed to exhibit poor degradation, tendency to accumulate, and prolonged clearance, leading to long-term toxicity in tissues and organs. Consequently, numerous articles and studies have emerged focusing on enhancing degradation capabilities through surface area tuning, surface modification, and silica framework tuning.40 In this context, biodegradable periodic mesoporous organosilica (BPMO), a type of MSN with a tunable silica framework, has been researched to enhance its biodegradability, relying on organic functional groups attached to the silica framework to form Si–O–Si bonds, facilitating the material's biodegradation.31 BPMO has chemically biodegradable linkages, including di- and tetra-sulfide bonds,41 while organic R groups within the framework can also enhance drug loading and release capabilities through interactions between the drug and nanoparticles.42 Contrariwise, studies on BPMO loaded with CDs are rare and have not been thoroughly investigated. Consequently, the composite of CDs with BPMO is used as a nanocarrier in synergistic bioimaging and chemotherapy applications, which will be the focus of this paper.
In this work, we conducted the green synthesis process of fluorescent carbon dots (CDs) from banana (Musa paradisiaca cv. Awak) juice through a microwave method that is much quicker and more convenient. For the first time, the synthesized CDs are incorporated into BPMO via the sol–gel method, forming BPMO@CDs. The physicochemical properties of the obtained BPMO@CDs are characterized by Fourier-transformed infrared spectroscopy (FTIR), powder X-ray diffraction (P-XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption isotherms. The fluorescence properties of the obtained nanoparticles are indicated by photoluminescence and UV-Vis spectroscopy, showing green and red fluorescence under appropriate excitation light. Furthermore, their effective internalization into MCF7 breast cancer cells and tracking ability via fluorescence are also demonstrated. Additionally, the biocompatibility and cytotoxicity of anticancer drug-loaded BPMO@CDs toward L929 fibroblast cells and MCF7 breast cancer cells indicated the promise of BPMO@CDs in the synergetic applications of bioimaging and chemotherapy.
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Fig. 1 A schematic of the (a) CD and (b) BPMO@CD synthesis process. TEM images of (c) BPMO, (d) CDs and (e) BPMO@CDs. |
Specific vibrational signals representative of functional groups are observed in the FT-IR spectra. The vibration at 1634 cm−1 may be attributed to CC and C
O bonds attached to the CDs on the material's surface.43 Furthermore, a signal indicative of C–O–C bond vibrations is found at 1413 cm−1. Additionally, CH2 group vibrations appear at 2926 cm−1, and CH2 rocking vibrations are observed at 1413 cm−1.44 The signals at 1271 cm−1 and 1043 cm−1 correspond to C–O stretching vibrations of the remaining C2/C3 carbohydrate chains.45 A distinctive signal at 909 cm−1 is characteristic of epoxy ring vibrations of CDs attached to BPMO.46 Moreover, the stretching vibration of Si–O–Si bonds is also noted at this 909 cm−1 position.31 Similar to CDs, the presence of –OH and C–O functional groups in BPMO@CDs enhances their dispersibility in solvents.19 The N–H and C
O functional groups observed contribute to surface states, playing a role in the luminescent properties of the material. Particularly noteworthy is that the FTIR spectra of BPMO@CDs exhibit an inheritance of signals, combining the characteristics of both source materials.
Based on the P-XRD results, the correlation peaks in the angular range of 10–40° indicate the preferential orientation along the (002) direction of CDs within the BPMO@CDs (Fig. 2b). The prominent diffraction peak at 2θ ∼ 22.90° corresponds to the (002) plane, revealing an interlayer spacing of approximately 0.388 nm. This result closely aligns with the CDs obtained using the microwave method with 2θ = 21.20°. The observed slight deviation (1.7°) in the diffraction peak suggests that CDs have infiltrated into the BPMO, indicating the successful binding of CDs to the BPMO particles while preserving the structural integrity of the CDs. In addition, the nitrogen adsorption–desorption isotherms of BPMO@CDs fit a type IV isotherm, which indicates that the mesoporous structure of BPMO is still retained after attachment with CDs (Fig. 2c). The surface area slightly reduced from 793.75 m2 g−1 to 770.91 m2 g−1. The TGA curve of the BPMO@CDs shows no significant difference, mirroring the curve of BPMO. Beyond 350 °C, the TGA of the BPMO@CDs exhibits a slight decrease in weight (less than 2%) compared to the initial BPMO due to the gradual decomposition of CDs binding to the BPMO (Fig. 2d).
The XPS spectrum of BPMO@CDs also demonstrates that the chemical state of BPMO@CDs is not significantly different from BPMO, with only a minor change observed: an additional peak appears at 288.78 eV, indicating the CO bond (Fig. 2e, f and Fig. S2, Table S1, ESI‡). Additionally, the elemental analysis results show the higher carbon content in BPMO@CDs (20.36%) compared to 18.94% of BPMO (Table S2, ESI‡).
The photoluminescence spectrum (PL) results (Fig. 3b) reveal the maximum fluorescence peaks in the green region, specifically at 505 nm and 522 nm, corresponding to CDs and BPMO@CDs when excited with light at 325 nm. From the absorption peaks in the UV-Vis results, it can be observed that the absorption peak of CDs (λmax = 283 nm) is greater than that of BPMO@CDs (λmax = 270 nm). Based on the photon energy formula E = hf = hc/λ, this paper proposes that the bandgap of BPMO@CDs molecules is smaller than that of CD molecules. As the bandgap (Eg) increases, the emitted energy also increases. Under the excitation energy, due to the smaller Eg of CDs compared to Eg of BPMO@CDs, the emission energy of BPMO@CDs may be greater than the emission energy of CDs. Consequently, it can be explained why BPMO@CDs, translating to a shorter wavelength, exhibit a lower photoluminescence peak at λPL = 505 nm compared to CDs at λPL = 522 nm. Fig. 3c illustrates the possible mechanism that could lead to the luminescent properties of CDs and BPMO@CDs.
The fluorescence properties of hybrid materials are clearly observed when exposed to the excitation light. In detail, BPMO@CDs exhibit vivid and distinct green and red fluorescence that results from CDs. However, their fluorescence intensity is not as strong and vibrant as that of pure CDs (Fig. 3d).
Fluorescence images of L929 and MCF7 cells incubated with BPMO@CDs are displayed in Fig. 4b. The nuclei are stained blue with Hoechst, while the BPMO@CDs exhibit green fluorescence. After 24 hours, the MCF7 cells showed a more intense and widespread green fluorescence signal compared to L929 cells, indicating higher nanoparticle uptake by cancer cells. This observation aligns with the quantitative uptake data presented in Fig. 4a.
From all the obtained results, BPMO@CDs can be used as multifunctional nanoparticles with BPMO as a nanocarrier due to high porosity and CDs with strong luminescence. Hence, BPMO@CDs are introduced for potential applications in the field of biomedical sciences, particularly in bioimaging and drug delivery.
Footnotes |
† Congratulations to Vietnam National University Ho Chi Minh City on its 30th Anniversary (1995–2025). |
‡ Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d4nh00633j |
This journal is © The Royal Society of Chemistry 2025 |