Tunable diblock copolypeptide hydrogel depots for local delivery of hydrophobic molecules in healthy and injured central nervous system

Many hydrophobic small molecules are available to regulate gene expression and other cellular functions. Locally restricted application of such molecules in the central nervous system (CNS) would be desirable in many experimental and therapeutic settings, but is limited by a lack of innocuous vehicles able to load and easily deliver hydrophobic cargo. Here, we tested the potential for diblock copolypeptide hydrogels (DCH) to serve as such vehicles. In vitro tests on loading and release were conducted with cholesterol and the anti-cancer agent, temozolomide (TMZ). Loading of hydrophobic cargo modified DCH physical properties such as stiffness and viscosity, but these could readily be tuned to desired ranges by modifying DCH concentration, amino acid composition or chain lengths. Different DCH formulations exhibited different loading capacities and different rates of release. For example, comparison of different DCH with increasing alanine contents showed corresponding increases in both cargo loading capacity and time for cargo release. In vivo tests were conducted with tamoxifen, a small synthetic hydrophobic molecule widely used to regulate transgene expression. Tamoxifen released from DCH depots injected into healthy or injured CNS efficiently activated reporter gene expression in a locally restricted manner in transgenic mice. These findings demonstrate the facile and predictable tunability of DCH to achieve a wide range of loading capacities and release profiles of hydrophobic cargos while retaining CNS compatible physical properties. In addition, the findings show that DCH depots injected into the CNS can efficiently deliver small hydrophobic molecules that regulate gene expression in local cells.     

负载DMOG的光交联明胶水凝胶的骨组织工程研究

目的：探讨负载DMOG(Dimethyloxallyl Glycine)的光交联明胶(Gelatin Methacryloyl,GelMA)水凝胶的促成骨分化的作用以及对大鼠颅骨骨缺损修复的效果。方法：制备GelMA-DMOG水凝胶后,扫描电镜下观察其表面特征,体外检测其降解时间;将小鼠成骨前体细胞(MC3T3-E1)培养于GelMA和GelMA-DMOG水凝胶表面,荧光观察细胞骨架形态,CCK-8法检测其细胞毒性;成骨诱导后,ALP,茜素红染色和qRT-PCR检测其对MC3T3-E1细胞成骨向分化的影响;构建大鼠颅骨骨缺损模型,4周和8周后观察GelMA和GelMA-DMOG水凝胶对骨缺损修复的效果。结果：与GelMA水凝胶相比,GelMA-DMOG水凝胶孔径大小、分布及降解时间并没有明显差异;两组水凝胶对MC3T3-E1细胞增殖无明显影响;与培养在96孔板上的对照组相比,GelMA组略微促进MC3T3-E1细胞成骨向分化,而GelMA-DMOG组明显增强了细胞的成骨向分化和成骨相关基因Runx2、ALP和OCN的表达;大鼠颅骨骨缺损体内实验发现与GelMA组相比,GelMA-DMOG水凝胶处理组具有明显的促成骨成血管作用和较好的骨缺损修复效果。结论：GelMA-DMOG水凝胶相对于GelMA材料自身的理化性能没有改变,且体外和体内实验显示该材料对于骨缺损修复具有较好的促进作用,为骨组织工程治疗骨缺损的临床应用开辟了新途径。     

Bioresorbable hydrogels prepared by photo-initiated crosslinking of diacrylated PTMC-PEG-PTMC triblock copolymers as potential carrier of antitumor drugs

PTMC-PEG-PTMC triblock copolymers were prepared by ring-opening polymerization of trimethylene carbonate (TMC) in the presence of dihydroxylated poly(ethylene glycol) (PEG) with Mn of 6000 and 10,000 as macro-initiator. The copolymers with different PTMC block Lengths and the two PEGs were end functionalized with acryloyl chloride. The resulting diacrylated PEG-PTMC-DA and PEG-DA were characterized by using NMR, GPC and DSC. The degree of substitution of end groups varied from 50.0 to 65.1%. Hydrogels were prepared by photo-crosslinking PEG-PTMC-DA and PEG-DA in aqueous solution using a water soluble photo-initiator under visible light irradiation. The effects of PTMC and PEG block lengths and degree of substitution on the swelling and weight loss of hydrogels were determined. Higher degree of substitution leads to higher crosslinking density, and thus to lower degree of swelling and weight loss. Similarly, higher PTMC block length also leads to lower degree of swelling and weight loss. Freeze dried hydrogels exhibit a highly porous structure with pore sizes from 20 to 100 µm.The biocompatibility of hydrogels was evaluated by MTT assay, hemolysis test, and dynamic clotting time measurements. Results show that the various hydrogels present outstanding cyto- and hemo-compatibility. Doxorubicin was taken as a model drug to evaluate the potential of PEG-PTMC-DA and PEG-DA hydrogels as drug carrier. An initial burst release was observed in all cases, followed by slower release up to more than 90%. The release rate is strongly dependent on the degree of swelling. The higher the degree of swelling, the faster the release rate. Finally, the effect of drug loaded hydrogels on SKBR-3 tumor cells was evaluated in comparison with free drug. Similar cyto-toxicity was obtained for drug loaded hydrogels and free drug at comparable drug concentrations. Therefore, injectable PEG-PTMC-DA hydrogels with outstanding biocompatibility and drug release properties could be most promising as bioresorbable carrier of hydrophilic drugs.     

Controlled release of fragrances from polymers I. Thermodynamic analysis

The feasibility of preparation of novel controlled release systems for the delivery of fragrances was investigated. The thermodynamic interactions of model substances which are typical constituents of fragrances with various copolymers were analyzed in the presence of a surrounding fluid. Conditions of favorable release were established by estimating the fragrance partition coefficient. Infinite dilution Flory interaction parameters of various fragrances in contact with a polymer or a surrounding fluid were determined. Generalized expressions were derived for the liquid lattice site sizes of various fragrance compounds.     

Thiol-ene crosslinking polyamidoamine dendrimer-hyaluronic acid hydrogel system for biomedical applications

A series of alkene functionalized polyamidoamine (PAMAM) dendrimers were synthesized to prepare in situ forming hydrogels with varied gelation time and mechanical properties through crosslinking with thiolated hyaluronic acid (HS-HA). By varying the alkenyl groups on the dendrimers, the gelation time displayed a large range from 8 seconds to 18 hours, and the modulus of the hydrogels ranged from 36 to 183 Pa under experimental conditions. Investigation by ¹H-NMR spectroscopy revealed that the gelation time and the stiffness of the hydrogels were governed by the degree of electron deficiency of alkenyl groups on the dendrimers. This research provided a systematic study on the relationship between chemical structures versus gelation time and mechanical properties of hydrogels, which could guide the way to synthesize in situ forming hydrogels with designated gelation time and stiffness for biomedical applications. Further, a RGD peptide was attached to the PAMAM dendrimers to enhance cell attachment and proliferation. Viability assays of Human Umbilical Vein Endothelial Cells (HUVEC) in the synthesized hydrogels demonstrated the biocompatibility of the hydrogels after 48 hours of culturing, and the RGD peptide improved the viability of HUVEC cells in hydrogels. We believe the PAMAM/HA hydrogel system is a tuneable and biocompatible system for diverse biomedical applications.     

Drug delivery systems based on biocompatible imino-chitosan hydrogels for local anticancer therapy

A series of drug delivery systems were prepared by chitosan hydrogelation with citral in the presence of an antineoplastic drug: 5-fluorouracil. The dynamic covalent chemistry of the imine linkage allowed the obtaining of supramolecular tridimensional architectures in which the drug has been homogenously dispersed. Fourier-transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WXRD) and polarized light microscopy (POM) measurements were used in order to follow the hydrogelation and drug encapsulation processes. The ability of the prepared systems to release the drug has been investigated by UV–Vis spectroscopy using a calibration curve and by fitting the results with different mathematic models. To mimic the behavior of the hydrogel matrix in bio-environmental conditions in view of applications, their enzymatic degradability was monitored in the presence of lysozyme. The in vivo side effects of the systems, in terms of their influence on the blood elements, biochemical and immune parameters were monitored on white Swiss mice by intraperitoneal administration of the injectable obtained hydrogels. All the characteristics of the obtained systems, such as micro-porous morphology, uniform drug encapsulation, enzymatic degradability, lack of side effects, other than the one of the drug itself, along with their ability to release the drug in a sustained manner proved that these material meet the requirements for the development of drug delivery systems, making them suitable for being applied in intraperitoneal chemotherapy.     

局部应用重组人Ⅲ型胶原蛋白水凝胶对糖尿病患者创面愈合的影响

目的探讨局部应用重组人Ⅲ型胶原蛋白水凝胶治疗糖尿病合并下肢难愈性创面的效果及其对创面炎症反应的影响。 方法选择2020年9月至2021年6月北京市化工职业病防治院医疗部收治的糖尿病合并下肢难愈性创面患者20例作为研究对象,采用随机数字表法分为试验组与对照组,每组各10例。在实施基础抗糖尿病治疗基础上,试验组局部外敷重组人Ⅲ型胶原蛋白水凝胶,对照组给予常规清创换药治疗,比较2组创面愈合率及创面组织肿瘤坏死因子-α(TNF-α)、白细胞介素-1β(IL-1β)、白细胞介素6(IL-6)及基质金属蛋白酶9(MMP-9)水平。 结果2组患者治疗后创面面积均较治疗前缩小,试验组患者治疗后7、14 d的创面愈合率分别为(34.00±2.53)%、(73.90±13.00)%,明显高于对照组(23.30±3.89)%、(48.30±6.30)%,差异均有统计学意义(t＝1.330、2.640,P<0.05);治疗后14 d,2组患者创面中TNF-α、IL-1β、IL-6、MMP-9水平较治疗前均降低,差异均有统计学意义(P<0.05),且试验组患者创面中TNF-α、IL-1β、IL-6、MMP-9的含量[(87.60±8.78)、(71.70±10.30)、(79.80±13.60)、(11.27±2.45)ng/L]均分别低于对照组[(111.60±9.86)、(81.10±8.03)、(96.90±14.50)、(15.05±2.82)ng/L],差异均有统计学意义(t＝－5.740、－2.260、－2.720、3.200,P<0.05)。 结论局部应用重组人Ⅲ型胶原蛋白水凝胶治疗糖尿病合并下肢难愈性创面,可有效提高创面愈合率,降低创面炎症反应,临床治疗效果显著。     

Physical characterisation and component release of poly(vinyl alcohol)-tetrahydroxyborate hydrogels and their applicability as potential topical drug delivery systems

Poly(vinyl alcohol)-tetrahydroxyborate (PVA-THB) hydrogels are dilatant formulations with potential for topical wound management. To support this contention, the physical properties, rheological behaviour and component release of candidate formulations were investigated. Oscillatory rheometry and texture profile analysis were used at room temperature and 37 °C. Results showed that it was possible to control the rheological and textural properties by altering component concentration and modifying the type of PVA polymer used. Hydrogels made using PVA grades with higher degrees of hydrolysis displayed favourable characteristics from a wound healing perspective. In vitro release of borate and PVA were assessed in order to evaluate potential clinical dosing of free species originating from the hydrogel structure. Component diffusion was influenced by both concentration and molecular weight, where relevant, with up to 5% free PVA cumulative release observed after 30 min. The results of this study demonstrated the importance of poly(vinyl alcohol) selection for ensuring appropriate gel formation in PVA-THB hydrogels. The benefits of higher degrees of hydrolysis, in particular, included lower excipient release and reduced bioadhesion. The unique physical characteristics of these hydrogels make them an appealing delivery vehicle for chronic and acute wound management purposes.     

Preparation,characterization and pharmacological evaluation of tolterodine hydrogels for the treatment of overactive bladder

In this study, transdermal gel formulations for tolterodine were developed to investigate the effects of gel matrix and chemical enhancers on drug skin permeation from tolterodine hydrogels. In vitro permeation studies of tolterodine through excised mouse skin were carried out using Franz-type diffusion cells. In the optimum gel formulation, Carbopol 940 was selected as the gel matrix. Compared to gels without enhancer, tolterodine hydrogels with N-methyl pyrrolidone (NMP) showed significant enhancing effect on transdermal permeation of tolterodine (p < 0.05). The results of in vitro percutaneous delivery experiment showed that the relationship of the steady accumulative percutaneous amount (Q, μg cm⁻²) of tolterodine hydrogels and time was Q_4–12h = 770.19t^1/2 − 966.99. Tolterodine permeated at the steady-state speed of 770.19 μg cm⁻² h⁻¹ and its release coincided with Higuchi Equation. The pharmacokinetic properties of the optimized tolterodine formulation were studied in rabbits. The absolute bioavailability of tolterodine was 11.47%. Since the absence of hepatic first-pass metabolism, only a single active compound-tolterodine was detected in the plasma. A skin irritation study was also carried out on rabbits, and the results showed tolterodine hydrogels had no skin irritation. In the pharmacodynamic study, the significant effects of tolterodine hydrogels on the inhibition of pilocarpine-induced rat urinary bladder contraction were last to 12 h, indicating that tolterodine hydrogels could produce prolonged pharmacological responses. In conclusion, tolterodine hydrogels were formulated successfully using Carbopol 940 and NMP and these results helped in finding the optimum formulation for percutaneous drug release. It is quite evident that tolterodine hydrogels may offer a possibility to avoid the first-pass effect, resulting in a single active compound of tolterodine in plasma, which may profit on the patient under the dose control and the reduction of potential adverse effect from two active compounds in the body.     

Gentamicin Release from Photopolymerized PEG Diacrylate and pHEMA Hydrogel Discs and Their In Vitro Antimicrobial Activities

Hydrogels based on poly(ethylene glycol)-diacrylate (PEG-DA) and 2-hydroxyethyl methacrylate (HEMA) were polymerized with cross-linking agent ethylene glycol diacrylate (EGDMA) under mild photoinitiating conditions. PEG-DA and HEMA concentrations of disks with 1 ± 0.3 mm thickness were 30% and 50% w/w and 40% and 60% w/w, respectively. Gentamicin sulphate was incorporated into the hydrogel during photopolymerization and its release kinetics were tested by spectrophotometric method at 255 nm wavelength in phosphate buffer (pH 7.4) and citrate buffer (pH 2.2). The drug release in citrate buffer was faster compared with to phosphate buffer. The release of drug from 40% HEMA containing hydrogel showed Fickian diffusion mechanisms in phosphate buffer (pH 7.4). Antimicrobial efficiency of the samples was tested by agar diffusion method in two different bacterial cultures (Pseudomonas aeruginosa [ATCC 10145], Staphylococcus aureus [ATCC 25923]). Inhibition zone diameter (mm) surrounding each sample was measured after 24 hr incubation of drug loaded disks onto agar plates at 37°C. Inhibition zone formation also confirms that gentamicin sulphate preserves its antimicrobial activity after subjected to photopolymerization conditions.