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Cancer is the most important leading cause of death worldwide, with about 10 million deaths caused by cancer in 2020. In situ gel drug delivery systems have attracted much attention in the field of pharmacy and biotechnology due to their good histo-compatibility, excellent injectability, high drug delivery capacity, slow-release drug delivery, and less influence by the in vivo environment. Meanwhile, in situ gel can be combined with chemotherapy, photo-thermal therapy, chemokinetic therapy, immunotherapy and so on to deliver drugs into the tumor site in a less invasive way without surgical operation, forming a semi-solid gel reservoir in the tumor site to realize in situ tumor combined therapy. In this paper, the author summarized the research progress of anti-tumor in situ gel delivery system in the past 10 years, introduced its commonly used polymer materials, classification principles and specific application examples, and finally summarized and discussed the key issues, in order to provide reference for the development of new anti-tumor drug delivery system in the future.
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Embolotherapy is a common method for clinical intervention in the treatment of diseases including aneurysms, arteriovenous malformations and solid tumors, and embolic agents are a decisive factor affecting the effect of embolization. Although various embolic agents like coils, microspheres, and Onyx have been used clinically, there are still some treatment limitations: such as weak blood vessel penetration, easy to aggregate, poor mechanical properties, adhesion to catheters, and the need for toxic solvents (e.g. dimethyl sulfoxide). In recent years, a number of studies have found that in situ hydrogels have good application prospects in the field of vascular embolization. When low viscosity precursor solution is injected into the targeted blood vessel via microcatheters, it will undergo a sol-gel transition through physical and/or chemical cross-linking to form hydrogel to block blood flow. In addition, these in situ hydrogels can load drugs by pore embedding, electrostatic interaction, chemical bonding, etc., and have excellent sustained-release properties. This review summarizes the research progress of injectable in situ hydrogel vascular embolic agents in the past ten years, with a view to provide references for the development of new embolic agents in the future.
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In this study, a novel oral drug delivery system based on linolenic acid-modified chitosan (CS-LA) micelle was developed to improve the oral bioavailability of doxorubicin (DOX), which was proven by its in vivo intestinal absorption in rats. The DOX-loaded CS-LA micelles (CS-LA@DOX) were prepared by the dialysis method. The synthesized micelle material was identified by proton nuclear magnetic resonance spectroscopy (1H-NMR) and Fourier transform infrared spectroscopy (FT-IR). A series of the micelle properties, including particle size distribution, zeta potential, encapsulation efficiency (EE), drug loading (DL), micromorphology, polymorphy, and critical micelle concentration (CMC) were characterized or tested. The in vitro release of micelles was observed by the dialysis method, and the absorption-promoting effect of micelles was investigated by intestinal circulation experiments in rats. The animal welfare and experimental procedures were in accordance with the regulations of the Animal Ethics Committee of Guilin Medical University. The results of 1H-NMR and FT-IR showed that CS and LA were covalently bound via an amide linkage. The DOX encapsulated in the micelle core was in an amorphous state. The as-prepared micelles in the transmission electron microscope (TEM) image showed regular spherical shapes and uniform sizes with a series of excellent characteristics including (119.2 ± 2.1) nm of mean particle size [polymer dispersity index (PDI), 0.190 ± 0.08], +12.1 mV of zeta potential, (70.23 ± 0.74) % of EE, (8.77 ± 0.02) % of DL and 51.75 μg·mL-1 of CMC. Compared with the reference, DOX hydrochloride, the proposed micelle drug delivery system showed an obvious sustained-release effect in vitro release; and enhanced drug absorption in the small intestine of rats.
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The intestinal absorption properties of the main effective components (glycyrrhizic acid, isoliquiritigenin, 6-gingerol, ginsenoside Rb1, atractylode-I) in Lizhong decoction (LZD) extracts were investigated with an in situ single-pass intestinal perfusion model in rats. UPLC-TQ-MS was used to determine the concentration of the five components in the intestinal perfusion. Animal welfare and experimental procedures were in accordance with the regulations of the Animal Ethics Committee of Nanjing University of Chinese Medicine. As evaluation indexes for the intestinal absorption characteristics, the absorption rate constant (Ka) and the apparent permeability coefficient (Peff) of the five main ingredients were analyzed. Results showed that the best absorption sites for glycyrrhizic acid, isoliquiritin and 6-gingerol were the ileum, colon and duodenum, respectively, and the differences between different intestinal segments were statistically significant (P <0.05). There was no notable difference in Ka and Peff between ginsenoside Rb1 and atractylode-I in the different intestinal segments (P > 0.05), suggesting that they were absorbed throughout. The five components were well-absorbed in the whole intestine (Peff > 1.0×10-3 cm·min-1), indicating that LZD is suitable for preparing sustained, controlled release and enteric-coated preparations.
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It is difficult to directly observe the structural transformation inside of soft capsules if their shells are opaque. This study was designed to noninvasively in situ measure the structural characteristics of the soft capsules and internal particle distributions to reveal the intrinsic quality of the soft capsules and develop a new technique for reverse engineering and the physical stability evaluation of the soft capsules. In this research, the CT projection images of soft capsules, namely, propolis soft capsules, were collected via synchrotron radiation X-ray micro computed tomography (SR-μCT). After three-dimensional reconstruction, the structural differences of the soft capsules under long-term test and accelerated test for 6 months were quantitatively analyzed by calculating the three-dimensional structure parameters such as volume, number and distribution of the particles inside and the thickness for the wall of the capsules. There were only a small number of particles evenly distributed in the soft capsules stored under common storage condition without layering. On the other hand, the shell wall of the soft capsule turned thinner locally at the occlusal portion and the particles with strong X-ray absorption were densely distributed at the edge of the capsule wall after the accelerated test. This study revealed that the structural parameters of soft capsules obtained by SR-μCT could be used to evaluate the influence of storage environment on the physical stability of soft capsules. The technology provides a new method for quality control and evaluation for the soft capsules.
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In this paper, a new type of preparation for treatment of initial dry eye disease, thermosensitive in situ gel, was prepared using levocarnitine as a model drug. Poloxamer 407 and poloxamer 188 were used as the gel matrix, and sodium hyaluronate and sodium carboxymethylcellulose were used as bioadhesive materials. Gelation temperature was determined by a rotor method and the prescription was optimized by central composite design-response surface methodology. The pH value, viscosity value and gelation temperature of the optimal prescription were measured. The release of the drug in vitro was examined by dialysis membrane permeation, and retention time of the thermosensitive in situ gel preparation on the rabbit's ocular surface was observed by a slit lamp microscope. The results showed that the dosage of the poloxamer 407 and poloxamer 188 were 20.81% and 3.46%, respectively, and sodium hyaluronate was 0.02%, sodium carboxymethyl cellulose was 0.10% of the optimal formulation of levocarnitine thermosensitive in situ gel. The pH value was 6.90 ± 0.06 at room temperature and the viscosity value started to rise sharply at 27 ℃ of the optimal formulation. The gelation temperature of the optimal preparation before and after dilution by simulated tear fluid were (26.37 ± 0.06) ℃ and (33.57 ± 0.21) ℃, respectively. In the first 240 min, in vitro release rate per unit area of levocarnitine thermosensitive in situ gel was lower than that of solution (P<0.05), and after 600 min, the cumulative release rate of levocarnitine thermosensitive in situ gel could reach more than 80%. The retention time of the thermosensitive in situ gel preparation on rabbit's ocular surface reached about 25 min, at least 5 times as much as that of the solution. The animal experiment was conducted following the National Institutes of Health Guidelines for the use of experimental animals, and approved by the Ethics Committee of the Experimental Animal Center of Beijing University of Chinese Medicine. The levocarnitine thermosensitive in situ gel showed good characteristics and sustained release property and significantly improved the retention time of the drug on the rabbit's ocular surface.