Smart Multifunctional Magnetic Nanoparticle-Based Drug Delivery

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Smart multifunctional magnetic nanoparticle-based drug delivery system for cancer thermo-chemotherapy and intracellular imaging Beibei Shen, Yuan Ma, Shiyong Yu, and Chenhui Ji ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b09772 • Publication Date (Web): 30 Aug 2016 Downloaded from http://pubs.acs.org on September 3, 2016

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ACS Applied Materials & Interfaces

Smart multifunctional magnetic nanoparticlebased drug delivery system for cancer thermochemotherapy and intracellular imaging Beibei Shen,† Yuan Ma,† Shiyong Yu*,† Chenhui Ji, † †

School of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021,

China. * Correspondence should be addressed to: [email protected]

KEYWORDS: Fe3O4, temperature responsive, hyperthermia, drug delivery, cell image,

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ABSTRACT

In this research, a thermo-responsive drug release system was synthesized, which encapsulated the magnetic nanoparticles Fe3O4 and the drug model 5-fluorouracil with thermo-sensitive polymer PNIPAM. Mesoporous SiO2 was used as the channel of drug release, which could enhance the rate of drug loading and reduce the loss of drug. Chitosan (CHI) is a natural cationic linear polymer. The results showed the successful coating of chitosan and rhodamine 6G on the surface of SiO2 sphere. The intermolecular interactions of the nanocomposites were confirmed by Fourier transform infrared spectroscopy. Rhodamine 6G (R6G) is a typical fluorochrome, which could be applied for the cell imaging. Fluorescent imaging studies by confocal laser scanning microscopy (CLSM) indicated that the prepared nanocomposites Fe3O4/PNIPAM/5Fu@mSiO2-CHI/R6G could specifically target to tumor cells. Therefore, our work showed great potential in drug delivery and cancer therapy. 1. INTRODUCTION With the high magnetization values, superparamagnetic iron oxide nanoparticles have been widely used in biomedical applications, such as hyperthermia, drug delivery, and cell separation, etc. 1-9 Due to the responses to the external magnetic field, Fe3O4 nanoparticles could be used as heater. In the area of cancer treatment, it offers a promising solution by hyperthermia therapy . It also could be coupled with drug-carrier system. Targeted drug delivery could also be realized by the driving of the particles under the external magnetic field. Mesoporous silica nanoparticle displays many excellent advantages in the field of biomedicine application. Such as the high biocompatibility, tunable mesoporous size and volume, high adsorption capacity of guest molecules and ease of surface modification, these advantages

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make it be a passive molecular transporter10, 11. However, it is short of the intelligent property of controlled drug release, which extremely demand in drug carriers. In most cases, the mechanism of stimulus-responsive was limited by irreversibility of drug delivery. Therefore, significant effort has been committed to the development of “smart” mesoporous silica-based drug delivery system.

12-15

For example, the release of drug model encapsulated in temperature sensitive

polymeric matrices is a classical approach for the sustained and controlled release of therapeutic molecules.16,17 Hae-Won Kim have reported a hybrid system Au@mSi-DOX@P, in which the temperature-sensitive poly(NIPAAm-co-BVIm) capped the pores of mSiO2 and the drug delivery could be controlled by temperature18. Herein, in the Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G system, the combination with intelligent temperature-sensitive polymer PNIPAM could optimize the process of drug adsorption and delivery.

19-22

PNIPAM displays a lower critical solution

temperature (LCST), the temperature at which the polymer goes through a reversible change of phase. When temperature is below the LCST, the polymer is in the swelling and hydrate conformation, while above the LCST, it is in the collapsed and dehydrated state.

23,24

The

property of reversible phase transition has been exploited in the application of drug delivery. As is known to all, chitosan is a natural polycationic polymer. Due to the excellent properties of biocompatibility, low toxicity, biodegradability, and high affinity for cell membranes, it has been widely researched in recent years as a primary material in the field of pharmaceutical and medical.

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The CHI backbone which is deacetylated has a high density of

amine groups. It allows electrostatic interactions with molecules which carry the negative charge under neutral pH conditions. Besides that, it was verified that the coating of chitosan could prevent the unexpected aggregation and improve the chemical stability of the system. Therefore, chitosan has been extensively used as drug carrier for low molecular drugs, protein and genes.26,

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Siling Wang reported a chitosan functionalized drug carrier CAR-CTS-SNM, in which the

biocompatible chitosan retardant the drug delivery effectively.28 Herein, as depicted in scheme 1, we reported the synthesis process of the temperature responsive drug carrier Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G and studied its potential as drug carrier at different temperature in vitro. In the drug delivery system, magnetic nanoparticles Fe3O4 were the source of magnetic, which could be used for hyperthermia treatment. The heating performances of Fe3O4, Fe3O4/PNIPAM/5-Fu@mSiO2 and Fe3O4/PNIPAM/5-Fu@mSiO2CHI/R6G were investigated under a magnetic field, respectively. Based on the magnetocaloric function of magnetic nanoparticles, the thermo-responsive drug delivery could be controlled under the magnetic field. The morphology and structure of Fe3O4/PNIPAM/5-Fu@mSiO2CHI/R6G were characterized by XRD, SEM, FT-IR, fluorescence spectrum and so on. It is obvious that the drug carrier Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G is low cytotoxicity and could be used for cell imaging potentially through the MTT assay and confocal laser scanning microscopy images.

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Scheme 1. (a). Illustration of the process of preparing Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G nanocomposites. (b). Schematic illustration showing the performance of temperature-switchable nanocomposites Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G in tumor cells.

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2. EXPERIMENTAL SECTION 2.1 Materials. N-isopropylacrylamide (NIPAM, 98%); cyclohexane (99.5%); 1,4-dioxane (99.5%); Azobis-iso-butyryl-nitrile(AIBN, 98%); ether absolute (99.5%); tetrahydrofuran (THF, 99%); ferrous sulfate heptahydrate (FeSO4·7H2O, 99%); ferric chloride hexahydrate (FeCl3·6H2O, 99%); hydrochloric acid (HCl, 36%); ammonia solution (NH3·H2O, 25%); potassium bromide (KBr, 99%); cetyltrimethylammonium bromide (CTAB, 99%); tetraethyl orthosilicate (TEOS, 99%); ammonium nitrate (NH4NO3, 99%); 5-fluorouracil (5-Fu, 99%); ethanol absolute (99.7%); sodium acetate trihydrate (CH3COONa·3H2O, 99%); acetic acid (CH3COOH, 36%); polyethylene glycol 4000 (PEG 4000, 99%); chitosan (CHI); rhodamine 6G (R6G); ethylene glycol; All reagents were of analytical grade. 2.2 Synthesis of Fe3O4 nanoparticles Fe3O4 nanoparticles were prepared by hydrothermal reaction. 2.7g of FeCl3·6H2O was dissolved in 80ml ethylene glycol and ultrasound for 30 minutes. Then added 2g PEG (4000) and 7.2g sodium acetate trihydrate into above solution under ultrasound for 30 minutes and immediately transferred to a autoclave and heated for 180℃. After 19 hours of reaction time, the precipitate was collected by magnet and washed with distilled water and ethanol absolute. 2.3 Synthesis of thermo-responsive polymer PNIPAM PNIPAM was synthesized by radical polymerization, which was according to the previous protocol with minor modification 29. 1.578g NIPAM and 0.0027g AIBN were added to 20ml 1,4dioxane with N2 bubbling. After 30 minutes, the bottle was sealed and placed to the oil bath at 70℃ to polymerization. After 17 hours, it was cooled to room temperature by ice. The production was

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precipitated in a large amount of ether and then dissolved in THF. To obtain the pure PNIPAM, it needed to repeat the processes of dissolving and precipitating once. 2.4 Synthesis of Fe3O4/PNIPAM/5-Fu@mSiO2 This step was aimed at preparing the thermo-responsive shell-core nanocomposite. 0.2g Fe3O4, 0.5g PNIPAM and 0.1g 5-Fu were added to 260ml ethanol solution under vigorous stirring at 37℃ for 30 minutes, which consisted of 100ml distilled water and 160ml ethanol absolute. Then 0.5g CTAB was dissolved into above solution with the vigorous stirring. After that, 2ml NH3· H2O was added in it to regulate the pH of the reaction environment. At last, 0.4ml TEOS was added to the above solution dropwise. After 6 hours, the production was obtained by magnet and washed with distilled water and ethanol absolute. 2.5 Synthesis of Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G 0.2g chitosan was dissolved in 36ml 0.2% CH3COOH solution and ultrasound for 30 minutes. Then 0.05g R6G was dispersed in it with ultrasound. Subsequently, 0.1g Fe3O4/PNIPAM/5-Fu@mSiO2 was added in the above solution under vigorous stirring. After 12 hours, the as-prepared Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G was collected by magnet and washed with distilled water and ethanol absolute. 2.6 In vitro drug release experiments In this experiment, 2 ml pH=5.0 PBS suspension of Fe3O4/PNIPAM/5-Fu@mSiO2CHI/R6G (0.05g/ml) was inserted into dialysis (molecular weight cutoff = 3500). This dialysis was floated vertically in a container of 10ml pristine PBS solution at 45℃. At the certain time intervals, 3ml of PBS suspension was taken out from the outer container and analyzed by UV-vis spectroscopy at 286 nm. As a control, the drug release experiment at 25℃ was performed by the same procedure.

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2.7 In vitro cytotoxicity assay of Fe3O4/PNIPAM@mSiO2-CHI/R6G nanocomposite The cytotoxicity of the Fe3O4/PNIPAM@mSiO2-CHI/R6G nanocomposite was evaluated by the MTT viability assay of 7901 cells, which followed standard protocols described by the manufacturer.

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7901 cells were seeded into a 96-well plate and subsequently cultured for 24

hours. Afterwards, the culture medium was replaced with a fresh medium containing the Fe3O4/PNIPAM@mSiO2-CHI/R6G at different concentrations (0, 6.25, 12.5, 25, 50, 100µg/ml). After cultured for 24 hours, the medium was removed again. 50µl MTT was added in each well and the cells were cultured for another 4 hours to allow the formation of formazan dye. Afterwards, 150 µl of DMSO was added to each well to dissolve the MTT formazan crystals. Then, the absorbance of each well was measured at a wavelength of 450 nm through a microplate reader. 2.8 In vitro imaging 7901 cells were used for testifying the process of cell imaging 31. Briefly, 7901 cells were seeded onto the 12-well plates at the density of 4x104 cells per well and incubated in media supplemented with 1% penicillin/streptomycin and 10% fetal bovine serum at 37 ℃ in 5% CO2 atmosphere for overnight. Then the cells were incubated with 0.2mg/ml Fe3O4/PNIPAM/5Fu@mSiO2-CHI/R6G nanocomposites for 2 hours and 4 hours, respectively, and then washed with PBS solution three times. At last, cells were mounted on clean glass slides using mounting solution and observed by confocal microscope imaging using the FV1000-X81 confocal microscope (Olympus).

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3. RESULTS AND DISCUSSION Fig. 1 showed the XRD patterns for the Fe3O4 nanoparticles (a), Fe3O4/PNIPAM/5Fu@mSiO2 (b) and Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G (c). Six characteristic peaks for Fe3O4 at 30.1°, 35.5°, 43.1°, 53.4°, 57.0°, and 62.6° were marked by their indices (220)，（311），（400），（422），（511）and (440).

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As shown in fig 1b and 1c, these peaks

were also observed in the Fe3O4/PNIPAM/5-Fu@mSiO2 and Fe3O4/PNIPAM/5-Fu@mSiO2– CHI/R6G, which indicated that coating process did not change the phase of Fe3O4. Because of the coating of amorphous SiO2, a bulge typical of silica at around 23° could be observed. 33

Compared with Fe3O4 (1a) and Fe3O4/PNIPAM/5-Fu@mSiO2 (1b), the intensity of peaks in

nanocomposites Fe3O4/PNIPAM/5-Fu@ mSiO2-CHI/R6G (1c) decreased a little, which was on account of the coating of chitosan hydrogel probably.

(c) Intensity(a.u.)

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(b) (311)

(220)

10

20

30

(400)

40

(511) (422)

50

(440)

60

(a)

70

80

2Theta(Degree)

Figure 1. The XRD patterns of Fe3O4 nanoparticles (a), Fe3O4/PNIPAM/5-Fu@mSiO2 (b), Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G (c).

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The morphology of Fe3O4 (2a), Fe3O4/PNIPAM/5-Fu@mSiO2 (2b) and Fe3O4/PNIPAM/5Fu@mSiO2-CHI/R6G (2c) were investigated by SEM. As shown in figure 2a, the Fe3O4 nanoparticles had a rough surface. Figure 2e-a showed that the diameter of the pure Fe3O4 was in a range of 220-290nm. Figure 2b revealed that the surface of Fe3O4/PNIPAM/5-Fu@mSiO2 was rather smooth, which indicated that Fe3O4 nanoparticles were coated by SiO2 shell successfully. In addition to this, figure 2e-b showed that the diameter of Fe3O4/PNIPAM/5-Fu@mSiO2 was in a range of 370-430nm, which was clearly much larger than pure Fe3O4. In figure 2c, the Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G microspheres with smooth surface were also well shaped spheres. In figure 2e-c, the average diameter of Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G was approximately to that of Fe3O4/PNIPAM/5-Fu@mSiO2, which testified that chitosan covered on the surface of SiO2 shell uniformly and slightly. Besides that, the EDS pattern of Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G showed all the element of it, in which the N element could be contributed to the chitosan.

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Figure 2. The SEM images of a: Fe3O4, b: Fe3O4/PNIPAM/5-Fu@mSiO2, c: Fe3O4/PNIPAM/5Fu@mSiO2-CHI/R6G, d: the EDS pattern of Fe3O4/ PNIPAM/5-Fu@mSiO2-CHI/R6G. e: the size

distributions

of

Fe3O4(2e-a),

Fe3O4/5-Fu/PNIPAM@mSiO2(2e-b),

Fe3O4/5-

Fu/PNIPAM@mSiO2-CHI/R6G(2e-c), which were dispersed in distilled water. The FTIR spectra of Fe3O4, Fe3O4/PNIPAM/5-Fu@mSiO2 and Fe3O4/PNIPAM/5Fu@mSiO2–CHI/R6G were showed in fig 3. In the spectrum of Fe3O4 (Fig 3a), the peak at 586 cm-1 was contributed to the Fe-O band.

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Figure 3b showed the C-H band and C-F band of -

CF=CH- at 808cm-1 and 1243cm-1 respectively, which were attributed to the anticancer drug 5fluorouracil. The peak at 970 cm-1 was assigned to the vibration of –CH3 in isopropyl, which indicated the existence of thermo-polymer PNIPAM. The spectrum (3b) displayed the Si-O band at 1086 cm-1,

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which confirmed that Fe3O4, 5-fluorouracil and PNIPAM were coated by SiO2

shell. It was consistent with the SEM image (fig. 2b). After modification with chitosan/rhodamine 6G hydrogel, figure 3c displayed the –CH3 band at 1384 cm-1 and -CH2band at 2925 and 2863 cm-1, which was the functional group of chitosan.36 The peak at 1611 cm1

was contributed to the band of -C=C- in the phenyl group, which belonged to the rhodamine 6G.

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(c) 590

2925 2863 1611

Transmittance（ %）

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1384

1101

(b) 808 970 586

1243 1086

(a)

586 3500

3000

2500

2000

1500

1000

500

-1

Wavenumber（ cm ）

Figure 3. FTIR spectra of (a) Fe3O4, (b) Fe3O4/PNIPAM/5-Fu@mSiO2, (c) Fe3O4/PNIPAM/5Fu@mSiO2 –CHI/R6G

The fluorescence spectra of Fe3O4, Fe3O4/PNIPAM/5-Fu@mSiO2 and Fe3O4/PNIPAM/5Fu@mSiO2–CHI/R6G were shown in figure 4, which were dispersed in distilled water (15mg/ml). There were no maximum emissions from Fe3O4 (a2) and Fe3O4/PNIPAM/5Fu@mSiO2 (b2), while being excited at the wavelength of 348nm. However, it exhibited that the maximum emission was achieved at 550nm from Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G (c2), which was also excited at 348nm. It is consistent with fact that the typical rhodamine framework emission peak is in the wavelength range from 525 to 660 nm. 37 It indicated that rhodamine 6G conjugated to the chitosan hydrogel successfully. Therefore, it could be used for the application of cell imaging potentially. This assumption was confirmed by the confocal laser scanning microscopy, which was described in fig 9 in details.

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348 550 Intensity(a.u.)

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(c2) (c1)

(b2)

(b1) (a1)

(a2)

350

550

600

Wavelength(nm)

Figure 4. The excitation spectra of Fe3O4 (a1), Fe3O4/PNIPAM/5-Fu@mSiO2 (b1), Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G (c1) and the emission spectra of Fe3O4 (a2), Fe3O4/PNIPAM/5-Fu@mSiO2 (b2), Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G (c2).

Fig 5 displayed the magnetic property of Fe3O4 nanoparticles (a), Fe3O4/PNIPAM/5Fu@mSiO2 (b) and Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G(c). The saturation in magnetization was 92.43 emu/g for Fe3O4, 54.26 emu/g for Fe3O4/PNIPAM/5-Fu@mSiO2 and 44.34 emu /g for Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G, respectively. Compared with Fe3O4 nanoparticles, the magnetization of Fe3O4/PNIPAM/5-Fu@mSiO2 and Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G decreased a lot, which was attributed to the reduced proportion of the magnetic core comparted to the whole mass of them. 38 It indirectly indicated that the magnetic core Fe3O4 was coated by SiO2 shell and chitosan/rhodamine 6G hydrogel. The result demonstrated that the nanocomposites still kept its sufficient responsiveness to magnetic field.

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Figure 5. Magnetization curves of Fe3O4 nanoparticles (a), Fe3O4/PNIPAM/5-Fu@mSiO2 nanocomposites (b) and Fe3O4/PNIPAM/5-Fu@mSiO2 –CHI/R6G nanocomposites(c).

Under

the

magnetic

field,

Fe3O4

(a),

Fe3O4/PNIPAM/5-Fu@mSiO2

(b)

and

Fe3O4/PNIPAM/5-Fu@mSiO2-CHI/R6G nanocomposites (c) got heated up due to the Neel and Brownian relaxation.39 Here, The time of heating up to 45℃(temperature of cancer therapy) at the concentration of 10mg/ml for Fe3O4, Fe3O4/PNIPAM/5-Fu@mSiO2 and Fe3O4/PNIPAM/5Fu@mSiO2-CHI/R6G was 130s, 222s and 298s, respectively. It was clear that the temperature of different nanocomposite (a, b, c) increased to 45℃ with different time under the external magnetic field of 37.68Oe. In addition to that, figure 6 also revealed that the speed of temperature increasing was also different at different concentration (15mg/ml and 10mg/ml). It was obvious that the speed of temperature increasing was the slowest for Fe3O4/PNIPAM/5Fu@mSiO2-CHI/R6G, which was contributed to the coating of chitosan hydrogel. The result was

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in accord with the magnetization curves (fig 5). The weaker in magnetization, the slower in heating up to 45℃.

Figure 6. Time-dependent temperature curves of Fe3O4 (a), Fe3O4/PNIPAM/5-Fu@mSiO2 (b) and Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G nanocomposites (c) at the magnetic field of 37.68Oe with concentration of 10mg/ml and 15mg/ml, respectively. 5-Fu was used as a drug model in the system. It was encapsulated by a thermo-sensitive smart polymer PNIPAM, which controlled drug delivery by the variation of temperature. Subsequently, drug loaded polymer PNIPAM was coated by SiO2 sphere, which could decrease the loss of drug in the blood stream. The drug delivery assay in vitro was studied at 25 °C (below LCST) and 45°C (greater than LCST) in the phosphate buffer solution(5.0). Figure 7 displayed the cumulative drug delivery of Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G. It was clear that the drug carrier at different temperature showed sustained drug release properties in phosphate buffer solution with different release rates. The continued release process at 25°C was much slower than that at 45°C. It was attributed to the reversible phase transition behavior of thermoresponsive polymer PNIPAM. When the temperature was higher than LCST, PNIPAM shrank in

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the aqueous solution and 5-Fu was squeezed out of SiO2 sphere. However, when the temperature was lower than LCST, PNIPAM expanded in the aqueous solution and 5-Fu was encapsulated in it. In the experiment, we set the quantity of cumulative drug release from the Fe3O4/PNIPAM/5Fu@mSiO2–CHI/R6G at 45 °C for 10 hours as the proportion of total drug released (100%). After incubation at 25 ℃ for 10 hours, the proportion of 5-Fu cumulative release from Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G was only 44%. Obviously, the process of drug delivery was in response to temperature. The higher temperature could improve the rate and quantity of drug delivery.

Figure 7. Drug release profiles of Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G nanocomposites at different temperature of 45℃(a) and 25℃(b). 7901 cells were used as the bioassay model in the MTT assay. It was obvious that the Fe3O4/PNIPAM@mSiO2–CHI/R6G nanocomposites had limited cytotoxicity up to a concentration of 100µg/ml in cell viability tests (fig 8.) The lowest cell viability value for

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Fe3O4/PNIPAM@mSiO2 –CHI/R6G nanocomposites was 75%, which suggested that it was low cytotoxicity for 7901 cell and could be applied for drug carrier potentially.

100

Cell Viability(% of NT)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


80

60

40

20

0

NT

6.25

12.5

25

50

100

Concentration(µ µg/ml)

Figure 8. Cell viability of 7901 cells after exposure to various concentrations of the Fe3O4/PNIPAM@mSiO2–CHI/R6G nanocomposites The cell imaging assay was assessed by confocal laser scanning microscopy (CLSM) analysis. The CLSM images were shown in fig 9. In bright field, it was obvious that all of the 7901 cells showed excellent photoluminescent property, which indicated that the drug carrier Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G had excellent function of targeting for 7901 tumor cells. This may be contributed to the special microenvironment of tumor cells. The environment of tumor cell membrane may tend to negative potential. And the potential of chitosan in the acid environment was positive potential. Therefore, the electronic interaction may facilitate drug carrier Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G target to 7901 cells. Compared with the incubation time (2h and 4h), it was obvious to find that the morphology of 7901 cells turned from polygon to circular. It reflected the process of cell death, which was owing to the delivery

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of anticancer drug 5-Fu from drug carrier Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G. In a word, the prepared carrier Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G has the potential application for cancer treatment.

Figure 9. Confocal laser scanning microscopy images of Fe3O4/PNIPAM/5-Fu@mSiO2– CHI/R6G nanocomposites loaded 7901 cells incubated for 2 hours and 4 hours, respectively. 4. CONCLUSIONS In summary, a thermo-responsive drug delivery system Fe3O4/PNIPAM/5-Fu@mSiO2– CHI/R6G was built. The synthesis and characterization of the system were illustrated in the context. Under the magnetic field, the nanocomposites performed the excellent ability of generating heat. It demonstrated that the system could be used for hyperthermia therapy

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potentially. The magnetic property of Fe3O4/PNIPAM/5-Fu@mSiO2–CHI/R6G was examined by JDAW-2000D VSM. The saturation in magnetization of Fe3O4/PNIPAM/5-Fu@mSiO2– CHI/R6G was 44.34emu/g. It showed that the system could be used for magnetic target therapy further. The drug delivery test indicated that drug was released mainly at 45℃, which was owing to the advantage of smart thermo-responsive polymer PNIPAM. The coating of CHI/R6G out of the silica shell could improve the stability and biocompatibility of the system. Besides that, the cell imaging experiment demonstrated that the system could be used for the monitoring of the therapeutic response in 7901 cells, which was attributed to the labeled of fluorescein rhodamine 6G. Therefore, the system would be a promising candidate for optical-imaging-based drug delivery system and could provide a new way in tumor cell and cancer treatment. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT The authors are grateful to the financial aid from the National Natural Science Foundation of China (Grant Nos. 20961006), Inner Mongolia Technology Innovation and Guidance Funds,

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Smart Multifunctional Magnetic Nanoparticle-Based Drug Delivery

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