| Environment stimuli-responsive polymer nanoparticle is a kind of intelligent material, which is able to undergo relatively large and abrupt physical or chemical changes in response to small external changes in the environmental conditions. Over the past decade, various responsive polymer nanoparticles have been explored as carries for drug delivery, biotechnology, genetic engineering, catalyst carriers as well as sensor applications. Although covalent responsive polymer nanoparticle has shown good performance,its preparation usually involves delicate design, multistep synthesis with low yield. Additionally, it is different to control size of nanoparticle and avoid aggregation. So the design of stimuli-responsive nanoparticles with optimizing properties to satisfy different applications is still an attractive issue at present.In this paper,we concentrated on develop a series of supramolecular nanoparticles (SNPs) by ionic self-assembly (ISA), which presents a promising solution to design various responsive materials with improved performance. ISA mainly employs the coulomb interaction to bind the oppositely charged tectonic units together, and complex architectures can be precisely tailored by selection of various functional constituents according to different applications. In addition, SNPs show favorable dispersion due to electrostatic repulsion of charge distributed surface. In this paper, self-assembly process, stimuli-responsive behaviors of SNPs as well as their applications in controlled release and fluorescence labeling were investigated in detail.At first, photoresponsive SNPs were fabricated by employing chitosan hydrochloride (CHC) and the photosensitive 4-oxo-4-(pyren-4-ylmethoxy) butanoic acid (PYBA) through ISA. The spherical nanoparticles structure and photosensitive properties were investigated by 1H NMR, optical photography, dynamic light scattering, SEM and fluorescent probe. A model guest, Nile red dye was loaded in the photosensitive SNPs. With UV light irradiation, dissociation and shrinkage of the SNPs occurred and release of loaded Nile red owing to breaking of chemical bonds in the PYBA. The result shows that 70% of the Nile red molecules were released out from the NPs with 1200 mW·cm-2 intensity of UV light for 50s irradiation. However, 13% of the Nile red molecules were released with 50 mW·cm-2 intensity of UV light for 180s irradiation. The releasing rate of Nile red molecules can be adjusted by changing UV light intensity. Moreover, near infrared laser irradiation can also control the release of Nile red molecules from PYBA-CHC nanoparticles by caused dissociation of nanoparticles.For real-time acquisition of crucial data of the guest molecules released from the delivery carriers,fluorescent SNPs were prepared through ISA of anthracene derivative (AN) and CHC. The AN-CHC nanoparticles show significant blue fluorescence due to introduction of AN. Then, antihypertensive drug Nicardipine was loaded in AN-CHC. Satisfactory DL (up to 35%) as well as high EE (up to 90%) was obtained, suggesting the high effective drug encapsulation capability of AN-CHC. Upon loading the drug, the strong blue fluorescence of AN-CHC was quenched due to fluorescence resonance energy transfer (FRET) and electron-transfer (ET). With release of drug in vitro, the fluorescence was recovered again. The recovered fluorescence intensity was heavily depend on accumulative drug release of AN-CHC, so one can readily monitor the drug release from FNPs by measuring fluorescence recovery in real-time. Moreover, AN-CHC exhibits the different release behavior upon the pH value. Drug release was easier at pH 7.4 than at pH 5.0, which suitable for controlling and monitoring the release of drug molecules in neutral physiological conditions (such as blood with pH 7.4).ISA technology is successful applied to fabricate polymer SNPs with mono-responsive property in above studies, such as photo or pH responsive. Nevertheless, SNPs with multi-responsive properties or functions have received much attention because of diversified environment change in practical applications. For tumor tissue caused interior stimulus of local temperature increase and extracellular pH decrease, we present a pH and thermo dual responsive SNPs as the anticancer drug doxorubicin (DOX) carriers for targeted delivery. These dual responsive nanoparticles were prepared based on ISA complexes of thermo sensitive poly (ionic liquids-co-N-isopropylacrylamide) with deoxycholic acid (DA). The aid of DA not only enables the nanoparticles with pH responsive property but also endows them with controllability in size and well dispersion in solution. These nanoparticles dissociate at pH5.2 for protonated DA molecules departing from ionic complexes. Additionally, LCST of nanoparticles solution is pH dependent, which is incline to decrease at weak acid environment. The in vitro release results show that DOX loaded nanoparticles stably disperse at pH 7.4, 37℃with few amount of drug release (ca.30%), and began to release large amount of drug release (more than 80%) at pH 5.2, 43℃to achieve targeting drug release. In cell cytotoxic activity study, DOX loaded nanoparticles show a significant effect on tumor inhibition.With unique chemical and physical properties, gold nanoparticles (GNPs) have attracted increasing interest in developing multifunctional materials with SNPs in biological and sensing applications. Based on SNPs of poly (ionic liquids-co-N-isopropylacrylamide) and deoxycholic acid (DA), a series GNPs loaded SNPs were further developed with different proportion of N-isopropylacrylamide. Then Nile dye molecules were loaded in SNPs to fabricate fluorescent probe. Under 808nm near infrared laser irradiation, the GNPs in SNPs can rapidly convert the laser energy into environmental heat due to strong Surface Plasmon Resonance (SPR), and high temperature induce squeezing the hydrophobic core of SNPs and facilitating fluorescence enhancement of encapsulated Nile red. The fluorescence intensity of Nile red can increase 15-fold after 15 min irradiation, which can effectively improve sensitivity of fluorescent probe. |
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