Article Cite This: Chem. Mater. XXXX, XXX, XXX−XXX
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Self-Healing Hydrogel with a Double Dynamic Network Comprising Imine and Borate Ester Linkages Yongsan Li,† Lei Yang,‡ Yuan Zeng,† Yuwei Wu,§ Yen Wei,† and Lei Tao*,† †
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The Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Tsinghua University, Beijing 100084, P. R. China ‡ Cancer Institute & Hospital, Peking Union Medical College & Chinese Academy of Medical Science, Beijing 100021, P. R. China § The 2nd Dental Center, Peking University School and Hospital of Stomatology, Beijing 100101, P. R. China S Supporting Information *
ABSTRACT: A self-healing hydrogel enriched with properties from a doubledynamic network (DDN) that has been prepared via two dynamic linkages (imine and borate ester) by using a single polymeric cross-linker. The fourcomponent Ugi reaction was used for easily synthesizing multifunctional poly(ethylene glycol) (MF-PEG) with a benzaldehyde group and phenylboronic acid group at each end of the chain. This MF-PEG simultaneously cross-linked with poly(vinyl alcohol) through the borate ester and glycol chitosan via an imine to generate a self-healing hydrogel with a unique DDN structure in seconds under mild conditions (pH ≈ 7, 25 °C). The prepared hydrogel showed enhanced strength and mucoadhesive abilities because of the complimentary interpenetrating dynamic networks. The DDN hydrogel showed satisfying biocompatibility and was further used in an in vivo mouse model. The hydrogel was injected to successfully deliver an antitumor drug and achieved a superior performance compared to traditional delivery methods. To the best of our knowledge, this is the first report of using the Ugi reaction to prepare a DDN self-healing hydrogel. We hereby propose a general strategy for the facile preparation of self-healing materials with improved properties. The strategy also opens a new avenue for synthesizing multifunctional/reinforced materials with the combination of dynamic chemistry and multicomponent reactions.
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INTRODUCTION Dynamic chemistry opens new opportunities to develop smart materials. Dynamic linkages in material structures can be broken and restored under certain conditions, leading to new materials with novel properties/functions.1−7 For example, thermosetting resins that are normally unrecoverable can be transformed into recyclable thermoplastic materials by including dynamic linkages in the resin networks.8−13 Moreover, hydrogels constructed with dynamic linkages normally possess interesting self-healing ability and can spontaneously repair internal/surface damages without external assistance.14−18 Varieties of self-healing hydrogels via different dynamic linkages have been developed and utilized in areas including as 3D cell matrix, drug carriers, and for tissue engineering.19−23 A self-healing hydrogel constructed via a dynamic imine linkage has been used as a new type of injectable hydrogel for drug delivery.24−27 Nowadays, selfhealing hydrogels are attracting more and more research attention. The development of new self-healing hydrogels via a different dynamic chemistry is of significance in fundamental research and has a high direct practical application value. A double-network (DN) hydrogel was introduced by Gong and co-workers in 2003.28 Two networks in the DN hydrogels complement each other to maintain structural integrity under external forces, resulting in hydrogels with remarkably reinforced mechanical strength, toughness, and ductility. © XXXX American Chemical Society
Many high-performance super-hydrogels have been fabricated according to the DN principle, suggesting that the combination of two networks is a general strategy to improve the properties of the hydrogels.29−32 Therefore, the combination of two dynamic networks appears as a feasible approach to prepare self-healing hydrogels with added value. To verify this concept, we report here a double-dynamic-network (DDN) self-healing hydrogel cross-linked by two dynamic linkages (Scheme 1). Imine and borate ester are well-known dynamic linkages.33−37 In neutral aqueous solutions, the fracture-regeneration balance of imine can form spontaneously. Many selfhealing hydrogels have been successfully developed via imine bond and utilized in biomedical areas.24,25,35 Meanwhile, the linkages between phenylboronic acid (PBA) and diol are normally stable under alkaline conditions and tend to decompose with decreased pH. The dynamic balance between PBA−diol linkages and PBA has also been employed to prepare self-healing hydrogels at neutral condition.22,38−42 For example, Anderson and co-workers reported a four-arm PBAterminated poly(ethylene glycol) (PEG) (PEG-PBA) and a four-arm diol-containing PEG (PEG-diol). These two polymers were mixed at pH 7 to successfully produce a Received: April 2, 2019 Revised: July 3, 2019
A
DOI: 10.1021/acs.chemmater.9b01301 Chem. Mater. XXXX, XXX, XXX−XXX
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Chemistry of Materials
can effectively introduce more than two functional components into polymer structures in one step, thus improving the synthesis efficiency. Here, we efficiently modified PEG with PBA and benzaldehyde groups via the Ugi reaction to easily prepare a telechelic multifunctional PEG (MF-PEG). This MF-PEG was used to simultaneously cross-link poly(vinyl alcohol) (PVA) and glycol chitosan (GC) via borate ester and imine linkages, respectively, resulting in a biocompatible self-healing hydrogel constructed by two dynamic networks. The resulting hydrogel had enhanced mechanical properties and adhesion ability because of the double-crosslinked dynamic networks. When used in an in vivo mouse model to deliver an antitumor drug, this hydrogel achieved a superior performance compared to traditional delivery methods. These results suggest that the DDN is a straightforward strategy to explore new self-healing hydrogels with improved properties for possible bioapplications.
Scheme 1. Schematic Illustration of a DDN Hydrogel with Imine and Borate Ester Linkages
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hydrogel via dynamic PBA−diol linkages. The resulting hydrogel is soft and moldable, and can be injected through a 21 G needle.22 These results suggest the potential of imine and borate ester in developing new smart biomaterials. However, a self-healing hydrogel constructed with both imine and borate ester linkages has been rarely reported. The Ugi reaction, introduced by Ivar Karl Ugi in 1959, involves an amine, a carboxylic acid, an aldehyde, and an isocyanide to rapidly generate α-aminoacyl amide derivatives with high yields.43 The Ugi reaction has been broadly studied to develop pharmaceutical and chemical libraries.44−47 Recently, the Ugi reaction has been used in polymer chemistry to prepare many elegant multifunctional (co)polymers.48−54 The Ugi reaction is superior to traditional two-component reactions in synthesizing multifunctional polymers because it
RESULT AND DISCUSSION Preparation of the MF-PEG. Briefly, PBA and acetalprotected benzaldehyde groups were simultaneously linked at both ends of the carbonylated PEG via the Ugi reaction followed by a simple hydrolyzation to achieve the target MFPEG (Figure 1a). First, a PEG derivative with terminal carboxylic acid (PEG-COOH) (Figure 1a,b) was prepared by a simple reaction between commercial PEG (Mn ≈ 2000 g mol−1) and o-phthalic anhydride. The integral ratio between the ester group (4.29 ppm) and the PEG moiety (3.88−2.98 ppm) was around 4/180, in agreement with the theoretical value (4/176). The MALDI-TOF analysis of the PEG-COOH confirmed that both PEG chain ends have been completely modified (Figure S1b). Then, the resulting PEG-COOH was
Figure 1. Preparation and NMR spectra (DMSO-d6, 400 M) of the PEG derivatives. (a) Reaction conditions: (i) carboxylic acid/aldehyde/amine/ isocyanide = 1:4:4:4, 45 °C, 24 h and (ii) 2 M HCl, 35 °C, 1 h. 1H and 11B NMR spectra of (b) PEG-COOH, (c) PEG intermediate, and (d) MFPEG. B
DOI: 10.1021/acs.chemmater.9b01301 Chem. Mater. XXXX, XXX, XXX−XXX
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Chemistry of Materials
Figure 2. (a) Gelation process of a DDN hydrogel. (b) Gelation times of the different hydrogels using the tube-inversion method. (c) Storage moduli of the hydrogels from the rheology tests. (d) Storage moduli and loss moduli of the different hydrogels. (e) SEM images of each hydrogel.
regenerated aldehyde group was clearly visible in the final MF-PEG (9.86 ppm, Figure 1d). The MF-PEG also had a clear signal in the 11B spectrum (Figure 1d, inset). The MALDITOF analysis confirmed the structure of the desired MF-PEG (Figure S1d). These results indeed indicate a smooth preparation of the target multifunctional polymer. Preparation of the DDN Hydrogel. The MF-PEG was mixed with GC or PVA to obtain two hydrogels under mild conditions (pH ≈ 7, 25 °C) (Figure S2c). However, when the PEG intermediate with PBA but no aldehyde at the chain ends was used, a hydrogel could only be formed with PVA but not with GC (Figure S2c). Similarly, a PEG derivative with terminal benzaldehydes (DA-PEG, prepared as previously described,14 Figure S2a,b) only generated a hydrogel with GC. The gelation mechanism was tested by small molecule model reactions (Figure S3). When PBA and glycerol were mixed at different pH (∼6, 7, 8), the peaks of borate ester could be identified in the 1H NMR spectra (Figure S3a). Similarly, the generation of imine at different pH was tested by mixing benzaldehyde and glucosamine (Figure S3b). The integral areas of borate ester and imine grew with increased pH values, confirming that both borate ester and imine are pH sensitive dynamic linkages. Thus, these results suggest the MF-PEG can cross-link GC or PVA to form hydrogels with different dynamic linkages: an imine between the aldehyde and the amine groups in GC or a borate ester between PBA and the diol groups in PVA.
used as the carboxylic acid component for the Ugi reaction with 4-(diethoxymethyl) benzaldehyde, 4-aminophenylboronic acid, and cyclohexyl-isocyanide in methanol (Figure 1a). The molar ratio of each component was PEG-COOH/4(diethoxymethyl)benzaldehyde/4-aminophenylboronic acid/ cyclohexyl-isocyanide = 1:4:4:4. Excess small molecular reagents were added to guarantee the complete reaction of the carboxyl acid groups in the polymer. The mixture was kept at 45 °C for 24 h. Then, the PEG intermediate was easily purified by simple precipitation in diethyl ether. The specific peak of the Ugi structure (6.36 ppm) could be clearly identified in the 1H NMR spectrum (Figure 1c). The integral ratio between the methine in the Ugi structures and the ester groups at the PEG chain ends (I6.36/I4.43 = 2/4.02) was consistent with the theoretical value (2/4). This suggests that the carboxyl acid groups have been nearly completely modified by the Ugi reaction (∼99%). The PEG intermediate was clearly seen in the 11B NMR spectrum (Figure 1c, inset), whereas PEG-COOH was not detected (Figure 1b, inset), suggesting the successful inclusion of PBA in the polymer structure after the Ugi modification. The MALDI-TOF analysis of the PEG intermediate confirmed the highly efficient conversion of the carboxyl acid groups (Figure S1c). Then, the MF-PEG target was obtained after the deprotection of the acetal groups in the PEG intermediate in a 2 M HCl aqueous solution (35 °C, 1 h). The acetal groups in the PEG intermediate (5.35 ppm, Figure 1c) completely disappeared after hydrolysis (Figure 1d, ∼99%). The C
DOI: 10.1021/acs.chemmater.9b01301 Chem. Mater. XXXX, XXX, XXX−XXX
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Chemistry of Materials Then, a DDN hydrogel was simply prepared by mixing PVA, GC, and MF-PEG aqueous solutions. The two dynamic linkages quickly generated under mild conditions (pH ≈ 7, 25 °C) led to the rapid formation of a double network hydrogel in several seconds (Figure 2a, Supporting Information Video). Correlation between Hydrogel Structures and Properties. The three components (PVA, GC, and MF-PEG) in the DDN hydrogel offer more tunable properties than other two-component hydrogels. Typically, different hydrogels with the same solid content (5.0 wt %) and the same amount of MF-PEG (2.5 wt %) were prepared by changing the ratios of GC and PVA. These hydrogels were named Gel 1 (PVA/GC: 2.5/0 wt %; amine/aldehyde: 0, diol/PBA: 18.2), Gel 2 (PVA/ GC: 2.0/0.5 wt %; amine/aldehyde: 1.6, diol/PBA: 14.5), Gel 3 (PVA/GC: 1.5/1.0 wt %; amine/aldehyde: 3.2, diol/PBA: 10.9), Gel 4 (PVA/GC: 1.0/1.5 wt %; amine/aldehyde: 4.8, diol/PBA: 7.3), Gel 5 (PVA/GC: 0.5/2.0 wt %; amine/ aldehyde: 6.4, diol/PBA: 3.6), and Gel 6 (PVA/GC: 0/2.5 wt %; amine/aldehyde: 8.0, diol/PBA: 0), respectively. The gelation time of these hydrogels, tested by the tube-inversion method, ranged from several seconds to several hundred seconds depending on the PVA/GC ratio (Figure 2b). More PVA resulted in a faster gelation time, indicating the quicker formation of the borate ester network compared to the imine network. The prepared hydrogels were kept for 3 h prior to rheological measurements. The storage moduli (G′s) of these hydrogels increased then decreased with the increasing amount of GC (Figure 2c,d; Figure S4). The scanning electron microscopy (SEM) images of these hydrogels confirmed that the DDN hydrogels (Gel 2−Gel 5) have denser internal networks than the single dynamic network (SDN) hydrogels (Gel 1, Gel 6) (Figure 2e). These results suggest that the interpenetrating networks in the DDN hydrogels effectively reduce the structural defects in the hydrogels. Thus, DDN hydrogels have more compact and more homogenous internal structures than the SDN hydrogels. As a result, the hydrogel with the densest internal structure had the highest storage modulus (Gel 4, G′ ≈ 5.7 kPa). Besides their strength, the mucoadhesive ability of hydrogels was tested using porcine intestinal mucosa as a model (Figure 3a). DDN hydrogels (Gel 2−Gel 5) have a stronger mucoadhesive ability than SDN hydrogels (Gel 1, Gel 6) (Figure 3b). Gel 4 has the strongest adhesive ability among all DDN hydrogels (Figure 3c). The mucoadhesive ability of PVA, GC, and PVA/GC solutions was also tested (Figure S5). The mucoadhesive strength of the PVA/GC mixture is higher than the sum of those of PVA and GC. This suggests a possible synergic effect between PVA and GC for adhesion, which might be caused by the multiple hydrogen bonding and/or polymeric entanglement between PVA and GC. These results confirm that the combination of two dynamic networks is valid to improve the properties of the hydrogels. Self-Healing Ability of DDN Hydrogels. The DDN hydrogels have self-healing and self-adapting properties from the two dynamic linkages. Gel 4, with the highest storage modulus among all hydrogels, was put in a syringe and pushed through a needle into a tree-shaped mold (Figure 4a1,a2). After 1 h, the hydrogel fragments assembled as the tree shape with a uniform structure (Figure 4a3,a4). This tree-shaped hydrogel was put into a syringe again and pushed through a needle into a star-shape mold (Figure 4a5,a6), and changed to the star shape without external assistance after 1 h (Figure 4a7,a8). The transformation from
Figure 3. (a) Schematic illustration of the mucoadhesive test. (b) Mucoadhesive strength evolution with the location on the hydrogel. (c) Mucoadhesive strength vs different hydrogels.
Figure 4. (a) Transformation experiment of Gel 4; (b) G′ and G″ of pieces of Gel 4 over time. (c) Ratio of G′s between self-healed and original Gel 4 hydrogels. The G′ of the original Gel 4 hydrogel is referred to as 100%. Data are represented as mean ± SD, n = 3.
tree-shape to star-shape qualitatively demonstrates the selfhealing and self-adapting ability of Gel 4. During the transformation experiment, a few pieces from the hydrogel mold were taken out for rheology analyses. After the first injection, the G′ of the Gel 4 hydrogel in the tree-shape mold dropped to 2.6 kPa. G′ gradually recovered and reached 5.6 kPa after about 45 min, which is very close to the original value for Gel 4 (G′ ≈ 5.7 kPa) (Figure 4b). This test was repeated; after each injection, the recovered hydrogels have nearly the same strength as the original hydrogel (Figures 4c, S6). These quantitative results confirm the excellent selfhealing ability of the Gel 4 hydrogel. D
DOI: 10.1021/acs.chemmater.9b01301 Chem. Mater. XXXX, XXX, XXX−XXX
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The biosafety of Gel 4 was tested in vivo. The Gel 4 hydrogel was injected under the skin of Balb/c mice (5-weekold females, 18−21 g; Figure S10). During a 4-day observation period, no inflammation or edema was noticed in the visual and anatomy observations (Figure S10a1,a2). Pathological analyses indicated that the tissue around the Gel 4 hydrogel was nearly the same as normal tissue and that the Gel 4 hydrogel does not cause allergic reactions (Figure S10b). Furthermore, the Gel 4 under the skin gradually degraded and only ∼8 wt % hydrogel remained after 18 days (Figure S11a,b). The mice injected with Gel 4 behaved normally during the 18day experiment. No diseased tissue was found around the injected hydrogel from the histological analyses (Figure S11c). These results confirmed that Gel 4 is a safe implantable material. Drug Delivery via a DDN Hydrogel for Tumor Therapy. A PBA-containing polymer has been used to deliver doxorubicin (Dox) because PBA moieties in the polymer structure can form the dynamic donor−acceptor coordination with the amino group of Dox.40,55,56 Here, an aqueous solution of Dox hydrochloride (Dox·HCl) and MF-PEG was prepared and adjusted to pH ≈ 7 by NaOH. This favors the hydrogel preparation at neutral condition and the formation of the donor−acceptor complex between PBA end groups in MFPEG and Dox. Gel 4 was used here as a typical DDN hydrogel to deliver Dox. The in vitro release of Dox from Gel 4 was studied (Figure S12). The cumulative concentration of Dox reached ∼93% after 21 days. This suggests that Gel 4 effectively prevents the sudden release of water-soluble Dox and instead achieves a gradual release of Dox. Next, an in vivo experiment was designed to simulate the postoperative chemotherapy for tumor using the Dox-loaded Gel 4 hydrogel. Pieces of human hepatocarcinoma tumor (MHCC97H) (∼50 mm3) marked with green fluorescent protein (GFP) were implanted under the armpit of the mice to mimic an incompletely resected tumor. Then, the Dox-loaded Gel 4 hydrogel (Dox-gel, 200 μL, Dox: 0.19 mg/mL) was injected at the tumor bed. A Dox saline solution (200 μL, Dox: 0.19 mg/mL) was used as the control either via intravenous administration (Dox-vein) or via direct injection at the tumor bed (Dox-situ). A saline solution injected in situ at the tumor bed served as the blank. During a 24-day period, no significant weight loss was observed in all groups (Figure S13). Optical and fluorescent images were recorded after the implantation of the tumor seeds (day-1, D1) and at the end of the treatments (day-24, D24), respectively (Figure 6a). In the Dox-gel group, the GFP signal in the tumor was very weak on D24. On the contrary, the GFP signals significantly increased in the blank (Figure 6a, saline) and the controls (Figure 6a, Dox-situ, Dox-vein). These results preliminarily suggest that the Dox in Gel 4 has a better tumor inhibition activity than Dox administered in solution. The tumors were removed on D24 and their size was measured. The tumor sizes were ranked as follows: saline ≈ Dox-vein > Dox-situ > Doxgel (Figure 6b). The tumor weights after different treatments also followed the same order (Figure 6c). These results confirmed the superior therapy results of the Dox-gel among all treatments. The drugs only have a therapeutic effect at certain concentrations. Therefore, according to the curves of tumor volumes throughout the experiment (Figure 6d), Dox-vein hardly inhibited any tumor growth, suggesting that intravenous
The shear-thinning properties of all hydrogels were also studied. The loss moduli (G″s) of all hydrogels became higher than G′ when the strain was more than 100% (Figure S7. For Gel 1, the critical strain is ∼1000%). This illustrates the breakage of the hydrogel networks under large strains. During the following step-changing experiments, the decreased storage moduli of all hydrogels under large strains (200% for Gel 2−6; 1000% for Gel 1) rapidly returned to the original level under a small strain (1%) (Figure S8). This suggests that the single or double dynamic networks confer self-healing properties to the hydrogels. Cytotoxicity and Biosafety of DDN Hydrogels. Subsequently, possible applications as new biomaterials for the DDN hydrogels were investigated. The cytotoxicity of the three components of the DDN hydrogels (PVA, GC, and MFPEG) was evaluated with the cell counting kit-8 assay (CCK8) for SMMC-7721 human hepatoma cells (Figure 5a).
Figure 5. (a) Cytotoxicity of the three components in the DDN hydrogels using a CCK-8 assay with an SMMC-7721 human hepatoma cell line. Data are represented as mean ± SD, n = 5, *p < 0.05, **p < 0.01, compared with the blank. (b1,b2) Cell viability after a 24 h culture with Gel 4 on the top (b1), and inside Gel 4 (b2).
The cells retained a considerable viability at a high concentration (16 mg/mL) of each component: ∼80% viability in MF-PEG and ∼100% in GC and in PVA. This confirms the low cytotoxicity of all three components of the DDN hydrogels. Next, a piece of the optimal Gel 4 hydrogel was put on the top of cells during culture. After 24 h, a fluorescein diacetate (FDA)/propidium iodide (PI) assay was performed to simultaneously observe live and dead cells (Figure 5b1). The cells had a high viability of ∼99%. Additionally, the cells were embedded in Gel 4 for 3D culture during 24 h (Figure 5b2). Only a few dead cells (red spots) were counted by the FDA/PI double-staining, indicating that most cells survived the 3D culture (∼96% viability). These results suggest that all components as well as the DDN hydrogel are low-toxic to human hepatoma cells. Similar results were obtained when L929 cells, a fibroblast cell line, were used (Figure S9). These validated the excellent cyto-safety of the DDN hydrogels. E
DOI: 10.1021/acs.chemmater.9b01301 Chem. Mater. XXXX, XXX, XXX−XXX
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In contrast, when Dox-gel was used, no obvious growth of the tumor seeds was observed during the whole experiment except for a false positive of increased volumes from the initial injection of the hydrogel (Figure 6d). Pathological analyses indicated that only Dox-gel effectively led to the necrosis of the cancer cells after 24 days (Figure S15). These results confirm the superior therapy result when using Gel 4 as an injectable drug carrier, which directly delivered the drug to the tumor position with a slow release and avoided the rapid clearance from the body experienced by the water-soluble drug. Traditional hydrogels prepared by covalent linkages have to be carefully designed to match the sizes of drugs and hydrogel meshes.57 On the contrary, self-healing hydrogels constructed by dynamic linkages are degradable (caused by the cleavage of the dynamic linkages instead of biodegradation). Thus, selfhealing hydrogels will gradually swell and decompose with fluid exchange. This is of benefit for the diffusion and dissolution of contained drugs to realize complete release. In the current research, the enhanced adhesive ability of Gel 4 is helpful for keeping the drug-loaded hydrogel at the desired site for continuous release.
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CONCLUSIONS In summary, we developed a straightforward strategy to facilely prepare multifunctional polymers by using the four-component Ugi reaction. A series of DDN hydrogels constructed via imine and borate ester linkages have been prepared, for the first time. These DDN hydrogels have an enhanced strength and mucoadhesive ability compared to SDN hydrogels. This suggests that the combination of the two dynamic networks is a valid strategy to improve the properties of hydrogels. These DDN hydrogels are self-healing and self-adapting because of the dynamic imine and borate linkages. They are also biocompatible and biosafe. When used as an injectable drugcarrier, a typical DDN hydrogel clearly showed a superior performance than the direct delivery of water-soluble Dox to the tumor by achieving a slow gradual release. This demonstrates the great potential of DDN hydrogels as biomaterials for biological and medical applications, which might prompt other in-depth studies of the dynamic chemistry for the preparation of other DDN hydrogels. At present, applications of dynamic chemistry in material science are continuously bringing new smart materials and renewing cognitions of traditional materials. The strategy of combining multiple dynamic linkages with multicomponent reactions might open new opportunities to manufacture other novel multifunctional smart materials.
Figure 6. (a) Optical and fluorescent images of the mice on day-1 and day-24. (b) Images of the tumors after different treatments. (c) Mass of the tumors after different treatments; data are represented as mean ± SD, n = 5, **p < 0.01, ***p < 0.001. (d) Tumor volume evolution over time, data are represented as mean ± SD, n = 5, *p < 0.05, **p < 0.01.
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EXPERIMENTAL SECTION
Preparation of DDN Hydrogels. A GC aqueous solution (5.0 wt %) was prepared by dissolving 0.5 g of GC in 8.0 g of water; this solution was neutralized using a HCl aqueous solution (37%) followed by adding water to 10 g. A PVA solution was prepared by dissolving PVA (0.5 g) into water (9.5 g). An MF-PEG aqueous solution (5.0 wt %) was prepared by adding MF-PEG (0.5 g) into water (9.0 g), then neutralizing by NaOH, and adding water to 10 g. All DDN hydrogels were prepared through the same procedure using different GC/PVA ratios. For example, to prepare Gel 2, a GC solution (0.1 g) was first mixed with a PVA solution (0.4 g); then an MF-PEG solution (0.5 g) was added. The mixture was stirred vigorously to generate a hydrogel in a few seconds. Cell Culture. SMMC-7721 cells were cultured in RPMI 1640 supplemented with 10% FBS and 1% penicillin at 37 °C in 5% CO2. The medium was changed every day. The cells were harvested with
injection was inefficient to deliver enough Dox to the tumor position. In addition, Dox-vein also resulted in a higher death rate than the other methods (Figure S14) and further indicated the risk of intravenous administration even though it is common in clinical practice. Dox-situ effectively suppressed the growth of the tumor seeds in the early stage of the experiment but lost function in a later stage. This might originate from water-soluble Dox clearing from the body, which negates the advantage of delivering a high concentration of Dox at the desired location via in situ injection. F
DOI: 10.1021/acs.chemmater.9b01301 Chem. Mater. XXXX, XXX, XXX−XXX
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Chemistry of Materials PBS-containing trypsin [0.025 (w/v) %] and EDTA [0.01 (w/v)%], centrifuged, and re-suspended in RPMI-1640 medium. L929 cells were cultured with the same method. Ethical Declaration. All in vivo tests were performed under the technical guidelines for nonclinical studies of cytotoxic antitumor drugs issued by the CFDA and authorized by the ethics committee of the Cancer Hospital, Chinese Academy of Medical Science (Approval number: NCL2018A166).
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.chemmater.9b01301.
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MALDI-TOF of the polymers, gelation mechanism, rheology, biosafety, controlled release tests of the hydrogels (PDF) Rapid formation of a double network hydrogel (MP4)
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Lei Tao: 0000-0002-1735-6586 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This research was supported by the National Science Foundation of China (21574073, 81671829, 81300851, 21788102). The authors thank Prof. Feng Shi (Beijing University of Chemical Technology) for mucoadhesive tests.
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REFERENCES
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DOI: 10.1021/acs.chemmater.9b01301 Chem. Mater. XXXX, XXX, XXX−XXX
