Article pubs.acs.org/Langmuir
Amphiphilic Polymerizable Porphyrins Conjugated to a Polyglycerol Dendron Moiety as Functional Surfactants for Multifunctional Polymer Particles Masako Moriishi, Yukiya Kitayama, Tooru Ooya, and Toshifumi Takeuchi* Graduate School of Engineering, Kobe University, 1-1, Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan S Supporting Information *
ABSTRACT: An amphiphilic polyglycerol dendron (PGD) conjugated porphyrin (PGP) bearing a polymerizable group was successfully synthesized. The PGP was used as an effective surfactant in emulsion and microsuspension polymerization systems to prepare styrene and methacrylate polymer particles, and the use of PGP provided the simple polymer particles with fluorescence derived from the metalloporphyrin and high colloidal stability due to the PGD. Furthermore, based on confocal laser scanning microscopy, we observed that the particles spontaneously formed a core−shell morphology with the PGP localized in the shell region during the polymerization and demonstrated drug loading in the shell region using rhodamine B as a model drug. The results indicate that the use of the functional surfactant PGP led to the preparation of multifunctional polymer particles from simple monomer species, and the resulting particles possessed high colloidal stability, fluorescence, and drug loading capability.
1. INTRODUCTION Surfactant design is very important for the synthesis of functional polymer particles because a surfactant is typically used for particle syntheses in emulsion1−8 and suspension (miniemulsion or microsuspension) polymerization9−16 systems, and surfactants are located at the particle/water interface, which decreases the interfacial free energy due to the amphiphilic property of surfactants. Therefore, the interfacial properties of polymer particles are primarily dependent on the surfactant properties. Polymer particles that bear multiple functional properties, such as high stability, fluorescence, and drug loading, are of great importance due to the advanced applications of these particles as drug delivery vehicles and in biological imaging.17−23 Most efforts toward achieving functional polymer particles have utilized polymer designs with versatile types of functional monomers as a standard approach, and a wide range of functional polymer particles have been reported using this approach.24−26 Nevertheless, the use of a functional surfactant has also been reported in the preparation of functional polymer particles. However, most of these surfactant designs were functionalizations via an addition of initiation or polymerizable groups to the surfactant, which are commonly termed “inisurf” and “surfmer”, to depress surfactant desorption from the polymer particles.27−30 Switchable surfactants, which can change their hydrophilicities by specific triggers such as altering the pH, CO2/N2 bubbling, and applying photoirradiation, have also been reported for widespread industrial fields.31−35 To date, there have been few reports regarding the synthesis of multifunctional surfactants that can be utilized in the preparation of multifunctional polymer particles from simple monomer species. © XXXX American Chemical Society
In this study, we synthesized a novel multifunctional surfactant, polyglycerol dendron (PGD) conjugated porphyrin (PGP), via a rational design to simultaneously endow simple polymer particles with multiple functions, such as high stability, fluorescence, and drug loading capability. Porphyrin has properties important for clinical use, such as fluorescence and the photosensitive ability to generate singlet oxygen, which enables porphyrin to be used as an anticancer drug.36−38 However, porphyrin is typically hydrophobic and difficult to use in an aqueous phase. PGD is known as a completely regulated branched hydrophilic polymer that has multiple hydroxyl groups on its surface, and these multiple hydrophilic groups lead to high solubility in water.39−41 Because this property results in a high excluded volume, PGD has been used for substrate modification to depress the nonspecific adsorption of proteins.42 In this study, we synthesized PGP, for use as a functional surfactant in emulsion and microsuspension polymerization systems to prepare multifunctional polymer particles from simple monomer species. Because it is important that surfactants are polymerizable to prevent their desorption from the polymer particles we also added polymerizable groups to the PGP to make it a polymerizable surfactant, which serendipitously resulted in the formation of a core−shell morphology with a PGP-rich shell region. This morphology produced drug loading capability in these simple polymer particles. Received: July 31, 2015 Revised: August 28, 2015
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DOI: 10.1021/acs.langmuir.5b02865 Langmuir XXXX, XXX, XXX−XXX
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Langmuir Scheme 1. Preparation Steps for Compound 4 (PGP)
HGLGPS (IX73, OLYMPUS, Tokyo, Japan) and a CCD camera (Zyla SCMOS, Andor Technology, USA)). UV−vis spectral measurements were performed using a V-560 spectrophotometer (JASCO Ltd., Tokyo, Japan). The particle internal morphology was observed using a confocal laser scanning microscope (IX81, OLYMPUS, Tokyo, Japan) at room temperature with an objective lens UPlanSApo (OLYMPUS, 60×, numerical aperture (NA) = 1.35), a multi Ar laser Opti λ 3360 (NTT Electronics, Kanagawa, Japan), and a GLS3135 (Showa Optronics, Tokyo, Japan). Elemental analysis for the particles was carried out using X-ray photoelectron spectrosopy (XPS) measurements (PHI X-tool, ULVAC-PHI, Inc., Kanagawa, Japan). 2.3. Synthesis of 5-(4-Aminophenyl)-10,15,20-tris(4methacryloyloxyphenyl)porphyrin (2) (Scheme 1). A solution of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (1) (0.14 g, 0.21 mmol) and DIEA (0.24 g, 1.89 mmol) was dissolved in dimethylformamide (DMF) (35 mL). Methacryloyl chloride (72 mg, 0.69 mmol) dissolved in DMF (2 mL) was added slowly to the solution at 0 °C under N2, and the reaction mixture was stirred at room temperature. After reacting overnight, the reaction mixture was diluted with water, and the product was extracted with DCM three times; then the organic layer was evaporated. The crude product was purified by silica gel column chromatography (AcOEt:hexane = 30:70 (v/v)) to obtain compound 2 as a purple solid. Fluorescent measurement was carried out with 420 nm excitation wavelength at 15 °C in DMF. Yield: 90 mg, 0.10 mmol, 49%. 1 H NMR (300.40 MHz, DMSO, ppm) δ 10.25 (s, 3H), 8.97 (s, 2H), 8.86 (s, 6H), 8.16 (s, 12H), 7.88 (d, 2H), 7.02 (d, 2H), 5.98 (s, 3H), 5.65 (s, 3H), 5.60 (s, 2H), 2.12 (s, 9H), −2.83 (s, 2H). MALDITOF-MS (matrix: 2,5-dihydroxybenzoic acid) calcd for [M + H]+ 880.02, found 880.06. 2.4. Synthesis of ZnII-5,10,15-tris(4-methacryloyloxyphenyl)20-(4-aminophenyl)porphyrin (3) (Scheme 1). Zinc(II) chloride (272 mg, 2 mmol) was dissolved in a mixture of chloroform (2 mL)
2. EXPERIMENTAL SECTION 2.1. Materials. 5,10,15,20-Tetrakis(4-aminophenyl)porphyrin (compound 1) (Scheme 1) and tetraethylthiuram disulfide were purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan). N,N′-Diisopropylethylamine (DIEA), n-butyl methacrylate monomer (BMA), rhodamine B, and zinc(II) chloride were purchased from Nacalai Tesque (Kyoto, Japan). Styrene, divinylbenzene (DVB), poly(vinyl alcohol) (PVA; degree of polymerization 1000, degree of saponification 88%) sodium hydroxide (NaOH), 4,6-dimethoxy-1,3,5triazine-2-yl)-4-methylmorpholinium chloride (DMT-MM), (2,2′azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate) (VA057), methacryloyl chloride, acetone, dichloromethane (DCM), ethyl acetate (AcOEt), hexane, methanol, chloroform, and dimethyl sulfoxide (DMSO) were purchased from Wako Pure Chemical Industries (Osaka, Japan). 2,5-Dihydroxybenzoic acid, potassium persulfate (KPS), and 2,2′-azobis(2-methylpropionamidine) dihydrochloride (V-50) were purchased from Sigma-Aldrich (USA). Deionized water used was obtained from a Millipore Milli-Q purification system. Glycerol dendron (third generation) (glycerol dendron G3) was prepared by the previously reported procedure.43 2.2. Apparatus. 1H NMR spectra were measured using a 300 MHz Fourier transform (FT) NMR apparatus (JNM-LA300 FT NMR system, JEOL Ltd., Japan). Matrix-assisted laser desorption/ionizationtime-of-flight (MALDI-TOF) mass spectra (MS) were measured using a MALDI-TOF MS apparatus (Voyager-DETM-1000, AB SCIEX, Japan). Fluorescence spectra were measured by a fluorescence spectrophotometer (F-2500, Hitachi High-Technologies Corp., Japan). The size and zeta (ζ) potential of particles were measured using a dynamic light scattering (DLS) apparatus (Zetasizer Nano ZS, Malvern Instruments Ltd., U.K.). The particle sizes and morphologies were observed using a scanning electron microscope (SEM) (VE9800, KEYENCE, Osaka, Japan). The particle morphology was also observed using an optical/fluorescent microscope with light source UB
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2.11. Drug Loading Application. P(S-PGP) emulsion dispersed in water (5 mg/mL, 400 μL), which was prepared by emulsion polymerization, was centrifuged and 200 μL supernatant was removed. MeOH solution of rhodamine B as a model drug (1 mM, 200 μL) was added to the P(S-PGP) emulsion. The P(S-PGP) and rhodamine B mixture (100 μL) was mixed with pure water (300 μL), and the P(SPGP) particles were collected by centrifugation. The remaining rhodamine B concentration in the supernatant was determined by UV−vis spectroscopy, where the sample supernatant was measured after 40 times dilution with water. The concentration was determined using the calibration curve of rhodamine B (0.625, 1.25, 2.5, 5.0, 10 μM) via UV−vis measurements at 554 nm in an aqueous solution. For PS particles, the same procedure was carried out as a reference experiment. P(S-PGP) particles prepared by microsuspension polymerization were used for a drug loading experiment using confocal laser scanning microscopy. Before the observation, the drug loading experiment was carried out by a similar procedure with P(S-PGP) particles prepared by emulsion polymerization as described above. For PGP excitation in confocal laser scanning microscopy, the observation was carried out with 405 nm excitation wavelength. An excitation wavelength of 559 nm was used for rhodamine B observations.
and DMF (2 mL). Compound 2 (90 mg, 0.10 mmol) dissolved in DMF (10 mL) was mixed with the solution and stirred overnight at 45 °C. The product was extracted with DCM and washed with water three times; then the organic layer was evaporated to obtain compound 3 as a green solid. Fluorescent measurement was carried out with 420 nm excitation wavelength at 15 °C in DMF. Yield: 94 mg, 0.10 mmol, 100%. MALDI-TOF-MS (matrix: 2,5-dihydroxybenzoic acid) calcd for [M + H]+ 943.40, found 943.27. 2.5. Synthesis of Glycerol Dendron G3 Coupled ZnII-5,10,15tris(4-methacryloyloxyphenyl)-20-(4-aminophenyl)porphyrin (4) (PGP) (Scheme 1). DMT-MM (36 mg, 0.13 mmol) was added to a mixture of compound 3 (94 mg, 0.10 mmol) and glycerol dendron G3 (71 mg, 0.12 mmol) dissolved in DMF (10 mL) and stirred overnight at 45 °C. After the solvent evaporation, the crude product was first purified by straight-phase column chromatography (AcOEt and MeOH) to remove the remaining compound 3 and the remaining DMT-MM. Then, the residue was purified by reversed-phase column chromatography (water/methanol: 40/60 (v/v)) to remove the remaining glycerol dendron G3 and to obtain compound 4 (PGP) as a green solid. Yield: 71 mg, 47 μmol, 47%. MALDI-TOF-MS (matrix: 2,5-dihydroxybenzoic acid) calcd for [M + H]+ 1519.00, found 1520.52. 2.6. Adsorption of PGP at Polystyrene (PS) Particles in Aqueous Media. To prepare PS particles, styrene (760 mg, 7.3 mmol), DVB (40 mg, 0.31 mmol), and KPS (41 mg, 0.15 mmol) were mixed with acetone/water (79.2 g, 45:55 (v/v)) in a 100 mL Schlenk flask. After N2/degas cycles, the emulsifier-free emulsion polymerization was carried out at 80 °C for 24 h with 1000 rpm stirring. After the polymerization, PS particles were washed with methanol three times. After mixing the obtained PS emulsion (1.0 mL, solid content 67 wt %) and PGP dissolved aqueous solution with 10% DMSO (1.0 mL, 0.362 mM), PS particles were collected and washed with water three times by centrifugation. The size and ζ potential of the PS particles were measured using DLS. 2.7. Determination of Critical Aggregation Concentration (CAC) for PGP. PGP aqueous solutions of various PGP concentrations (14.1, 74.1, 90.1, 104, 361, and 643 μM) were prepared. The size distributions for these aqueous solutions were measured using DLS after filtration (0.2 μm). 2.8. Emulsion Polymerization of Styrene with V-50 or VA-57 as an Initiator. The typical procedure is described below. Styrene (500 mg, 4.8 mmol), PGP (6.26 mg, 4.12 μmol), and V-50 (26 mg, 93.6 μmol) were added to water (49.5 g) in a 100 mL Schlenk flask, and emulsion polymerization was carried out at 80 °C for 24 h with stirring at 1000 rpm under N2/degas cycles to prepare P(S-PGP) particles. In the case of VA-057, styrene (1500 mg, 14.4 mmol), PGP (6.26 mg, 4.12 μmol), VA-057 (33 mg, 96.7 μmol), NaOH (7 mg, 175 μmol), and water (48.5 g) were used as ingredients of the emulsion polymerization. As a reference, PS particles were also prepared by emulsion polymerization of styrene under the same conditions without using PGP. Conversions of the polymerization were estimated by gravimetry. 2.9. Microsuspension Polymerization of BMA and Styrene with PGP as a Surfactant. The typical procedure is described below. BMA or styrene (0.2 g), PGP (5 mg, 3.3 μmol), and tetraethylthiuram disulfide (7.2 mg, 2.4 μmol) were mixed, and the solution was mixed with PVA aqueous solution (2 wt %, 1 g). After vortexing for 2 min, the emulsion was placed between glass plates with silicone rubber. The photoinduced polymerization was carried out with a 365 nm LED light (ZUV-C10, OMRON) for 1 h at room temperature. The obtained particles were washed with methanol and water twice. As a reference, microsuspension polymerization of BMA and styrene was demonstrated under the same conditions without using PGP. 2.10. Particle Swelling Test for P(S-PGP) and PS Particles. P(S-PGP) or PS particles, which were prepared by emulsion polymerization (1 mg/mL, 1 μL), were mixed with methanol (1 mL) in a plastic cell for DLS measurement, and the particle sizes were measured every 2 min starting 4 min after the mixing.
3. RESULTS AND DISCUSSION We synthesized PGP from 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (compound 1) as a starting material (Scheme 1). The amino groups in compound 1 were reacted with methacryloyl chloride to introduce polymerizable groups, and a three methacryloyl substituted porphyrin (compound 2) was collected by column chromatography. The introduction of a ZnII ion into compound 2 afforded compound 3 and resulted in a blue shift in the fluorescent spectrum due to the formation of a metalloporphyrin (Figure S1 in Supporting Information). Finally, the coupling reaction between the remaining amino group of compound 3 and the carboxylic acid at the PGD core yielded PGP. The introduction of PGD resulted in higher water solubility compared to the originally hydrophobic porphyrin, which has low water solubility, as shown in Figure 1.
Figure 1. Photographs of aqueous solutions containing compound 1 (a) and PGP (b).
To confirm the amphiphilic property of PGP, its adsorption onto poly(styrene-co-DVB) (P(S-DVB)) particles was investigated in a dispersed aqueous system, where the P(S-DVB) particles were synthesized via emulsifier-free emulsion polymerization with KPS in an acetone/water mixture (45:55 v/v) at 80 °C for 24 h. After mixing the aqueous solution of PGP containing 10% DMSO with the P(S-DVB) emulsion, the particles maintained a high stability. In addition, the diameter slightly increased (dn ca. 166 nm) from the original particle size (dn ca. 148 nm) (Figure S2), indicating that PGP was adsorbed on the P(S-DVB) particles via hydrophobic interactions and C
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Langmuir Scheme 2. Emulsion Polymerization in the Presence of PGP for Multifunctional Polymer Particles
Figure 2. Particle size distributions (a, b) and SEM images (c, d) of PS particles prepared via emulsion polymerization using VA-057 as an initiator without (a, c) and with (b, d) PGP in aqueous media.
π−π stacking in the aqueous medium. Furthermore, to confirm the amphiphilic property using a different method, we prepared styrene droplets using PGP as the surfactant in an aqueous medium. After homogenization, stable styrene droplets were successfully formed (Figure S3), indicating that the PGP was amphiphilic, and the use of PGP resulted in a high colloidal stability due to steric hindrance derived from the PGD group. We further demonstrated the application of PGP as a functional surfactant in emulsion polymerization (Scheme 2). First, we investigated the critical aggregation concentration (CAC) of PGP, and various concentrations of PGP in an aqueous solution (i.e., 14.1, 74.1, 90.1, 104, 361, and 643 μM) were employed. The size of PGP in the aqueous media was determined using DLS, and the size was nearly constant (volume-average particle size (dv) ca. 78 nm) at concentrations greater than 74.1 μM. In contrast, the size decreased to dv ca. 11 nm, according to a shift of the main peak to a smaller size, as the concentration of PGP was decreased to 14.1 μM (Figure S4). These results indicate that the CAC is between 14.1 and 74.1 μM. The CAC value was clearly small compared to the previously reported cationic surfmer based on alkyl ammonium
(1.0 mM)44 and anionic surfmer based on alkylbenzenesulfonate (ca. 3.2−6.0 mM).45 The emulsion polymerization of styrene was carried out with PGP and V-50 as the surfactant and cationic initiator, respectively, in an aqueous medium at 80 °C for 24 h and with 85 μM PGP, which is higher than the CAC. In these conditions, a small part of styrene seems to be solubilized in the hydrophobic region of the PGP aggregates, which may work as main polymerization loci in the emulsion polymerization. The obtained P(S-PGP) particles exhibited high stability, and the average dv was ca. 110 nm (polydispersity index (PDI) 0.139) at 77% conversion, which was smaller than that of the PS particles prepared without PGP (dv 319 nm, PDI 0.003, conversion 17%) (Figure S5); the polymerization without PGP resulted in an even lower conversion. This result indicated that the PGP effectively acted as a surfactant in the emulsion polymerization of styrene. The successful synthesis of stable P(S-PGP) particles via emulsion polymerization with PGP was also achieved when the initiator was changed to VA-057 with 2 equiv of NaOH. In this case, the size of the particles (dv 155 nm, PDI 0.091, conversion 71%) was much smaller than that of the PS (dv 587 nm, PDI 0.048, conversion 42%) prepared in D
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Langmuir the absence of PGP (Figure 2). The higher conversion attained in the emulsion polymerization of styrene with PGP implies that PGP enhanced the particle stability, which led to an increase in the number of polymer particles.1,46 After washing by centrifugation, the PS particles prepared using PGP exhibited fluorescence with an emission peak located at 620 nm (the excitation wavelength was 420 nm) (Figure 3), indicating that the PGP was copolymerized with the PS particles during the emulsion polymerization.
Figure 4. Optical (a, b) and confocal laser scanning (c, d) microscopy images of PBMA particles prepared by microsuspension polymerization using tetraethylthiuram disulfide as a photoinitiator without (a, c) and with (b, d) PGP in aqueous media. Figure 3. Fluorescent spectra of PS particles (1 mg/mL in water, excitation wavelength 428 nm, 10 °C) prepared via emulsion polymerization using VA-057 without (a) and with (b) PGP.
surfactant led to the further functionalization of the obtained particles. The PGP localized in the shell region may be more hydrophilic due to the PGD group, and the three polymerizable groups of PGP may have resulted in a cross-linked shell region. Therefore, we first performed a swelling test with the P(S-PGP) particles in methanol by mixing the P(S-PGP) aqueous emulsion (1 μL, 1 mg/mL) with methanol (1 mL); methanol is a good solvent for PGP but a poor solvent for PS. The size of the P(S-PGP) particles in methanol (dv 141 nm, PDI 0.158) was greater than that in the aqueous phase (dv 110 nm, PDI 0.139) (Figure 5). In addition, according to a time course, the P(S-PGP) particle size remained nearly the same only directly after being mixed with methanol (Figure S9). In contrast, the PS reference particles did not exhibit an increase in particle size after being mixed with methanol (Figure 5). These results indicate that the increase in the size of the P(S-PGP) particles was not caused by particle aggregation. However, the PGP localized shell region of the P(S-PGP) particles swelled with methanol. This swelling property was exploited for drug loading in the shell layer using rhodamine B as a model compound. After removing the supernatant, the P(S-PGP) particles were mixed with a rhodamine B methanol solution (20 μL, 1 mM). After the addition of water (1 mL) and further centrifugation, the P(S-PGP) particles were red due to the rhodamine B. The rhodamine B concentrations in the supernatant were 103 and 30 μM after mixing with the PS and P(S-PGP) particles, respectively, which, in the case of the P(S-PGP) particles, was clearly less than the original concentration of rhodamine B (125 μM), indicating that the rhodamine B was effectively loaded into the P(S-PGP) particles. To obtain direct evidence of rhodamine B loading into the PGP localized in the shell region, confocal laser scanning microscopy observation was performed using micrometer-sized P(S-PGP) particles prepared by microsuspension polymerization (Figure S10). The results indicated that the fluorescent signals derived from the PGP and rhodamine B (excitation and fluorescent spectra are shown in Figure S11) were both only observed in the shell region of the P(S-PGP) particles, and the fluorescent regions derived from both compounds were completely concordant, indicating that rhodamine B was successfully loaded into only the shell layer of
To expand the application of PGP, a microsuspension polymerization of BMA was also performed using PGP as a cosurfactant, in which micrometer-sized BMA droplets with high colloidal stability were prepared by homogenization with PVA as a stabilizer. After photopolymerization using tetraethylthiuram disulfide as a photoinitiator at room temperature, micrometer-sized spherical P(BMA-PGP) particles were obtained and confirmed using an optical micrograph (Figure S6). In addition, the fluorescent peak corresponding to PGP was observed with the prepared P(BMA-PGP) (Figure S7). Therefore, a fluorescence microscopy image was successfully obtained when the PGP was used as a cosurfactant in the microsuspension polymerization of BMA (Figure S6). In contrast, the PBMA particles prepared in the absence of PGP were not observed in the fluorescence micrograph because the PBMA particles were not fluorescent. The most interesting factor in the microsuspension polymerization of BMA with PGP is whether PGP was located at the particle/water interface due to its amphiphilic property. XPS measurements of the Zn 2p3 orbital were performed for the P(BMA-PGP) and PBMA particles, and the resulting peak derived from Zn 2p3 of the metalloporphyrin was only observed for P(BMA-PGP), indicating that PGP was contained in the shell layer (Figure S8). To obtain direct evidence, the P(BMAPGP) particles prepared by microsuspension polymerization were observed using confocal laser scanning microscopy, and a strong fluorescent intensity was confirmed only in the particle shell region. PGP can be copolymerized only in the monomer droplets because a hydrophobic initiator was used in the polymerization; therefore, only adsorbed PGP at the monomer/water interface was able to be copolymerized. These results strongly support the conclusion that PGP exhibits interfacial activity and is localized at the interface after copolymerization with BMA in the microsuspension polymerization system, leading to a core−shell morphology with a PGP-rich shell region (Figure 4). The discovery of the formation of a core−shell morphology in the obtained polymer particles when PGP was used as a E
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Figure 5. Particle size distributions of the PS (a) and P(S-PGP) (b) particles prepared by emulsion polymerization using VA-057 as an initiator without (a) and with (b) PGP in aqueous media.
Figure 6. Confocal laser scanning microscopy images of P(S-PGP) particles (top) and PS particles (bottom) after rhodamine B loading.
the P(S-PGP) particles (Figure 6). The loading of rhodamine B was not observed for the PS particles. The results indicate that the hydrophobic interaction as well as π−π interaction between rhodamine B and the PS matrix was negligible. Therefore, drug loading only occurred in the shell layer of the P(S-PGP) particles. The interaction between PGP and rhodamine B was also investigated by UV measurements (Figure S12). The UV spectra were unchanged after the addition of rhodamine B, and the peak wavelength was completely the same. The results indicate that the rhodamine B loading into the PGP-rich shell region happened in the swollen state and was finally trapped via the shrinking of the shell region.
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4. CONCLUSIONS PGP was successfully prepared for use as a novel multifunctional surfactant. The obtained surfactant was amphiphilic with high water solubility. In addition, this surfactant was successfully applied as a functional surfactant in emulsion and microsuspension polymerization systems to prepare multifunctional polymer particles from simple monomer species. The
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.langmuir.5b02865. Part of the experimental section including styrene droplet formation with PGP, fluorescent measurements, and interaction between PGP and rhodamine B. Materials including fluorescent spectra for 2, 3, and PS, P(S-PGP), PBMA, and P(BMA-PGP) particles, particle size
obtained particles exhibited high stability without coagulation, indicating that PGP acted as an effective stabilizer. In addition, based on confocal laser scanning microscopy results, the polymer particles spontaneously formed a core−shell morphology with a PGP-rich shell region. The shell region exhibited drug loading capability. Therefore, the use of a designed PGP as a surfactant enabled the synthesis of multifunctional polymer particles with high stability, fluorescence, and drug loading capability.
ASSOCIATED CONTENT
S Supporting Information *
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(12) Klinger, D.; Landfester, K. Stimuli-responsive microgels for the loading and release of functional compounds: Fundamental concepts and applications. Polymer 2012, 53 (23), 5209−5231. (13) Kitayama, Y.; Kagawa, Y.; Minami, H.; Okubo, M. Preparation of Micrometer-Sized, Onionlike Multilayered Block Copolymer Particles by Two-Step AGET ATRP in Aqueous Dispersed Systems: Effect of the Second-Step Polymerization Temperature. Langmuir 2010, 26 (10), 7029−7034. (14) Kitayama, Y.; Yorizane, M.; Minami, H.; Okubo, M. Iodine Transfer Polymerization (ITP with CHI3) and Reversible Chain Transfer Catalyzed Polymerization (RTCP with Nitrogen Catalyst) of Methyl Methacrylate in Aqueous Microsuspension Systems: Comparison with Bulk System. Macromolecules 2012, 45 (5), 2286−2291. (15) Zetterlund, P. B.; Alam, M. N.; Minami, H.; Okubo, M. Nitroxide-mediated controlled/living free radical copolymerization of styrene and divinylbenzene in aqueous miniemulsion. Macromol. Rapid Commun. 2005, 26 (12), 955−960. (16) Takimoto, K.; Takano, E.; Kitayama, Y.; Takeuchi, T. Synthesis of Monodispersed Submillimeter-Sized Molecularly Imprinted Particles Selective for Human Serum Albumin Using Inverse Suspension Polymerization in Water-in-Oil Emulsion Prepared Using Microfluidics. Langmuir 2015, 31 (17), 4981−4987. (17) Langer, R. Drug delivery and targeting. Nature 1998, 392 (6679), 5−10. (18) Stuart, M. A. C.; Huck, W. T. S.; Genzer, J.; Muller, M.; Ober, C.; Stamm, M.; Sukhorukov, G. B.; Szleifer, I.; Tsukruk, V. V.; Urban, M.; Winnik, F.; Zauscher, S.; Luzinov, I.; Minko, S. Emerging applications of stimuli-responsive polymer materials. Nat. Mater. 2010, 9 (2), 101−113. (19) Bae, Y.; Kataoka, K. Intelligent polymeric micelles from functional poly(ethylene glycol)-poly(amino acid) block copolymers. Adv. Drug Delivery Rev. 2009, 61 (10), 768−784. (20) Horcajada, P.; Chalati, T.; Serre, C.; Gillet, B.; Sebrie, C.; Baati, T.; Eubank, J. F.; Heurtaux, D.; Clayette, P.; Kreuz, C.; Chang, J. S.; Hwang, Y. K.; Marsaud, V.; Bories, P. N.; Cynober, L.; Gil, S.; Ferey, G.; Couvreur, P.; Gref, R. Porous metal-organic-framework nanoscale carriers as a potential platform for drug delivery and imaging. Nat. Mater. 2010, 9 (2), 172−178. (21) Kataoka, K.; Harada, A.; Nagasaki, Y. Block copolymer micelles for drug delivery: design, characterization and biological significance. Adv. Drug Delivery Rev. 2001, 47 (1), 113−131. (22) Veiseh, O.; Gunn, J. W.; Zhang, M. Q. Design and fabrication of magnetic nanoparticles for targeted drug delivery and imaging. Adv. Drug Delivery Rev. 2010, 62 (3), 284−304. (23) Biju, V. Chemical modifications and bioconjugate reactions of nanomaterials for sensing, imaging, drug delivery and therapy. Chem. Soc. Rev. 2014, 43 (3), 744−764. (24) Oh, J. K.; Drumright, R.; Siegwart, D. J.; Matyjaszewski, K. The development of microgels/nanogels for drug delivery applications. Prog. Polym. Sci. 2008, 33 (4), 448−477. (25) Ryu, J. H.; Chacko, R. T.; Jiwpanich, S.; Bickerton, S.; Babu, R. P.; Thayumanavan, S. Self-Cross-Linked Polymer Nanogels: A Versatile Nanoscopic Drug Delivery Platform. J. Am. Chem. Soc. 2010, 132 (48), 17227−17235. (26) Davis, M. E.; Chen, Z.; Shin, D. M. Nanoparticle therapeutics: an emerging treatment modality for cancer. Nat. Rev. Drug Discovery 2008, 7 (9), 771−782. (27) Li, W. W.; Yoon, J. A.; Matyjaszewski, K. Dual-Reactive Surfactant Used for Synthesis of Functional Nanocapsules in Miniemulsion. J. Am. Chem. Soc. 2010, 132 (23), 7823−7825. (28) Guyot, A.; Goux, A. Styrene emulsion polymerization in the presence of a maleate-functional surfactant. J. Appl. Polym. Sci. 1997, 65 (12), 2289−2296. (29) Greene, B. W.; Sheetz, D. P.; Filer, T. D. In-Situ Polymerization of Surface-Active Agents on Latex Particles.1. Preparation and Characterization of Styrene/Butadiene Latexes. J. Colloid Interface Sci. 1970, 32 (1), 90−95.
distributions obtained from DLS measurements, XPS measurements for PBMA and P(BMA-PGP), particle size vs time plot in the particle swelling test, SEM images for PS and P(S-PGP) particles, excitation and fluorescent spectra of rhodamine B, and UV−vis spectra for investigation of the interaction between PGP and rhodamine B (PDF)
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[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was partially supported by a Grant-in-Aid for Young Scientific Research (B) from the Japan Society for the Promotion of Science (JSPS) (given to Y.K.) and also partially supported by the Support Program from a Grant-in-Aid for Scientific Research (Grant 25288054) from JSPS. This work was performed in part under the Cooperative Research Program of “Network Joint Research Center for Materials and Devices” with Prof. Takehiko Wada at Tohoku University, Japan. The authors thank SYSTEM INSTRUMENTS Co., Ltd. (Tokyo, Japan) for their financial support.
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REFERENCES
(1) Gilbert, R. G. Emulsion Polymerization: A Mechanistic Approach; Elsevier Science & Technology Books: Amsterdam, 1995. (2) Ferguson, C. J.; Hughes, R. J.; Nguyen, D.; Pham, B. T. T.; Gilbert, R. G.; Serelis, A. K.; Such, C. H.; Hawkett, B. S. Ab initio emulsion polymerization by RAFT-controlled self-assembly. Macromolecules 2005, 38 (6), 2191−2204. (3) Okubo, M.; Sugihara, Y.; Kitayama, Y.; Kagawa, Y.; Minami, H. Emulsifier-Free, Organotellurium-Mediated Living Radical Emulsion Polymerization of Butyl Acrylate. Macromolecules 2009, 42 (6), 1979− 1984. (4) Kitayama, Y.; Moribe, H.; Kishida, K.; Okubo, M. Emulsifier-free, organotellurium-mediated living radical emulsion polymerization (emulsion TERP) of methyl methacrylate with dimethyl ditelluride as the catalyst. Polym. Chem. 2012, 3, 1555−1559. (5) Tonnar, J.; Lacroix-Desmazes, P. Use of sodium iodide as the precursor to the control agent in ab initio emulsion polymerization. Angew. Chem., Int. Ed. 2008, 47 (7), 1294−1297. (6) Fowler, C. I.; Jessop, P. G.; Cunningham, M. F. Aryl Amidine and Tertiary Amine Switchable Surfactants and Their Application in the Emulsion Polymerization of Methyl Methacrylate. Macromolecules 2012, 45 (7), 2955−2962. (7) Colver, P. J.; Colard, C. A. L.; Bon, S. A. F. Multilayered Nanocomposite Polymer Colloids Using Emulsion Polymerization Stabilized by Solid Particles. J. Am. Chem. Soc. 2008, 130 (50), 16850− 16851. (8) Rieger, J.; Stoffelbach, F.; Bui, C.; Alaimo, D.; Jerome, C.; Charleux, B. Amphiphilic poly(ethylene oxide) macromolecular RAFT agent as a stabilizer and control agent in ab initio batch emulsion polymerization. Macromolecules 2008, 41 (12), 4065−4068. (9) Asua, J. M. Miniemulsion Polymerization. Prog. Polym. Sci. 2002, 27 (7), 1283−1346. (10) Ma, G. H.; Sone, H.; Omi, S. Preparation of uniform-sized polystyrene-polyacrylamide composite microspheres from a W/O/W emulsion by membrane emulsification technique and subsequent suspension polymerization. Macromolecules 2004, 37 (8), 2954−2964. (11) Landfester, K. Miniemulsion Polymerization and the Structure of Polymer and Hybrid Nanoparticles. Angew. Chem., Int. Ed. 2009, 48 (25), 4488−4507. G
DOI: 10.1021/acs.langmuir.5b02865 Langmuir XXXX, XXX, XXX−XXX
Article
Langmuir (30) Ottewill, R. H.; Satgurunathan, R. Nonionic Lattices in Aqueous-Media 0.1. Preparation and Characterization of Polystyrene Lattices. Colloid Polym. Sci. 1987, 265 (9), 845−853. (31) Saji, T.; Hoshino, K.; Aoyagui, S. Reversible Formation and Disruption of Micelle by Control of the Redox State of the Head Group. J. Am. Chem. Soc. 1985, 107 (24), 6865−6868. (32) Liu, Y. X.; Jessop, P. G.; Cunningham, M.; Eckert, C. A.; Liotta, C. L. Switchable surfactants. Science 2006, 313 (5789), 958−960. (33) Dexter, A. F.; Malcolm, A. S.; Middelberg, A. P. J. Reversible active switching of the mechanical properties of a peptide film at a fluid-fluid interface. Nat. Mater. 2006, 5 (6), 502−506. (34) Minkenberg, C. B.; Florusse, L.; Eelkema, R.; Koper, G. J. M.; van Esch, J. H. Triggered Self-Assembly of Simple Dynamic Covalent Surfactants. J. Am. Chem. Soc. 2009, 131 (32), 11274−11275. (35) Sakai, H.; Matsumura, A.; Yokoyama, S.; Saji, T.; Abe, M. Photochemical switching of vesicle formation using an azobenzenemodified surfactant. J. Phys. Chem. B 1999, 103 (49), 10737−10740. (36) O’Connor, A. E.; Gallagher, W. M.; Byrne, A. T. Porphyrin and Nonporphyrin Photosensitizers in Oncology: Preclinical and Clinical Advances in Photodynamic Therapy. Photochem. Photobiol. 2009, 85 (5), 1053−1074. (37) Ethirajan, M.; Chen, Y. H.; Joshi, P.; Pandey, R. K. The role of porphyrin chemistry in tumor imaging and photodynamic therapy. Chem. Soc. Rev. 2011, 40 (1), 340−362. (38) Hill, J. S.; Kahl, S. B.; Stylli, S. S.; Nakamura, Y.; Koo, M. S.; Kaye, A. H. Selective tumor kill of cerebral glioma by photodynamic therapy using a boronated porphyrin photosensitizer. Proc. Natl. Acad. Sci. U. S. A. 1995, 92 (26), 12126−12130. (39) Yang, S. K.; Shi, X. H.; Park, S.; Ha, T.; Zimmerman, S. C. A dendritic single-molecule fluorescent probe that is monovalent, photostable and minimally blinking. Nat. Chem. 2013, 5 (8), 692−697. (40) Yang, S. K.; Shi, X. H.; Park, S.; Doganay, S.; Ha, T.; Zimmerman, S. C. Monovalent, Clickable, Uncharged, Water-Soluble Perylenediimide-Cored Dendrimers for Target-Specific Fluorescent Biolabeling. J. Am. Chem. Soc. 2011, 133 (26), 9964−9967. (41) Zheng, Y.; Li, S.; Weng, Z.; Gao, C. Hyperbranched polymers: advances from synthesis to applications. Chem. Soc. Rev. 2015, 44 (12), 4091−4130. (42) Wyszogrodzka, M.; Haag, R. Synthesis and Characterization of Glycerol Dendrons, Self-Assembled Monolayers on Gold: A Detailed Study of Their Protein Resistance. Biomacromolecules 2009, 10 (5), 1043−1054. (43) Haag, R.; Sunder, A.; Stumbe, J. F. An approach to glycerol dendrimers and pseudo-dendritic polyglycerols. J. Am. Chem. Soc. 2000, 122 (12), 2954−2955. (44) Cao, N.; Wang, X.; Song, L.; Zhang, Z. C. Nanopore microspheres prepared by a cationic surfmer in the miniemulsion polymerization of styrene. J. Polym. Sci., Part A: Polym. Chem. 2007, 45 (24), 5800−5810. (45) Herold, M.; Brunner, H.; Tovar, G. E. M. Polymer nanoparticles with activated ester surface by using functional surfmers. Macromol. Chem. Phys. 2003, 204 (5−6), 770−778. (46) Kitayama, Y.; Moribe, H.; Minami, H.; Okubo, M. Emulsifierfree, organotellurium-mediated living radical emulsion polymerization of Styrene: Initial stage of polymerization. Polymer 2011, 52 (13), 2729−2734.
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DOI: 10.1021/acs.langmuir.5b02865 Langmuir XXXX, XXX, XXX−XXX
