Remineralization potential of fully demineralized dentin infiltrated with silica and hydroxyapatite nanoparticles

Objective

This study investigates the potential of a novel guided tissue regeneration strategy, using fully demineralized dentin infiltrated with silica and hydroxyapatite (HA) nanoparticles (NPs), to remineralize dentin collagen that is completely devoid of native hydroxyapatite.

Methods

Dentin blocks were fully demineralized with 4 N formic acid and subsequently infiltrated with silica and HA NPs. The remineralizing potential of infiltrated dentin was assessed following a twelve week exposure to an artificial saliva solution by means of TEM, EDS and micro-CT. Measurements were taken at baseline and repeated at regular intervals for the duration of the study to quantify the P and Ca levels, the mineral volume percentage and mineral separation of the infiltrated dentin specimens compared to sound dentin and non-infiltrated controls.

Results

Infiltration of demineralized dentin with nano-HA restored up to 55% of the P and Ca levels at baseline. A local increase in the concentration of calcium phosphate compounds over a period of twelve weeks resulted in a higher concentration in P and Ca levels within the infiltrated specimens when compared to the non-infiltrated controls. Remineralization of demineralized dentin with silica NPs by immersion in artificial saliva was the most effective strategy, restoring 20% of the P levels of sound dentin. Micro-CT data showed a 16% recovery of the mineral volume in dentin infiltrated with silica NPs and a significant decrease in the mineral separation to levels comparable to sound dentin.

Significance

Demineralized dentin infiltrated with silica NPs appears to encourage heterogeneous mineralization of the dentin collagen matrix following exposure to an artificial saliva solution.     

Polymer nanoparticles for enhanced immune response: Combined delivery of tumor antigen and small interference RNA for immunosuppressive gene to dendritic cells

In this study, we report on polymer nanoparticles (NPs) that can induce an enhanced immune response in dendritic cell (DC)-based cancer immunotherapy by the combined delivery of tumor antigen and small interference RNA (siRNA) for the immunosuppressive gene to DCs. DCs are specialized antigen-presenting cells (APCs) that capture, process and present antigens and induce an antigen-specific cytotoxic T lymphocyte response. Because the suppressor of cytokine signaling 1 (SOCS1) is a negative regulator of the APC-based immune response, the inhibition of SOCS1 gene expression is essential for DCs to enhance antigen-specific anti-tumor immunity. Multifunctional poly(lactide-co-glycolic acid) (PLGA) NPs that can deliver tumor antigen and siRNA for immunosuppressive SOCS1 genes to DCs simultaneously were fabricated by the emulsion solvent evaporation method. We have found that the encapsulation efficiency of small-sized and hydrophilic SOCS1 siRNA into hydrophobic PLGA matrix is drastically enhanced by the help of a tumor model antigen such as ovalbumin (OVA), and the encapsulation efficiency of siRNA in PLGA (SOCS1 siRNA only) NPs and PLGA (OVA/SOCS1 siRNA) NPs was ∼2% and 57.6%, respectively. PLGA (OVA/SOCS1 siRNA) NPs were efficiently taken up by bone-marrow-derived dendritic cells (BMDCs) and showed no detectable toxic effect. The knockdown of SOCS1 in BMDCs by PLGA (OVA/SOCS1 siRNA) NPs enhanced pro-inflammatory cytokine (tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), IL-12 and IL-2) expression. Additionally, PLGA (OVA/SOCS1 siRNA) NP-treated BMDCs could elicit an immune response through cross-presentation in OVA-specific CD8 T cells that express IL-2 cytokine. Taken together, the combined delivery of NPs that can deliver both tumor antigen and immunosuppressive gene siRNA to BMDCs simultaneously could be a potent strategy to enhance immunotherapeutic effects in BMDC-based cancer therapy.     

A novel animal model to evaluate the ability of a drug delivery system to promote the passage through the BBB

The purpose of this investigation was to explore the potentiality of a novel animal model to be used for the in vivo evaluation of the ability of a drug delivery system to promote the passage through the blood–brain barrier (BBB) and/or to improve the brain localization of a bioactive compound. A Tween 80^®-coated poly-l-lactid acid nanoparticles was used as a model of colloidal drug delivery system, able to trespass the BBB. Tacrine, administered in LiCl pre-treated rats, induces electrocorticographic seizures and delayed hippocampal damage. The toxic effects of tacrine-loaded poly-l-lactid acid nanoparticles (5 mg/kg), a saline solution of tacrine (5 mg/kg) and an empty colloidal nanoparticle suspension were compared following i.p. administration in LiCl-pre-treated Wistar rats. All the animals treated with tacrine-loaded nanoparticles showed an earlier outcome of CNS adverse symptoms, i.e. epileptic onset, with respect to those animals treated with the free compound (10 min vs. 22 min respectively). In addition, tacrine-loaded nanoparticles administration induced damage of neuronal cells in CA1 field of the hippocampus in all treated animals, while the saline solution of tacrine only in 60% of animals. Empty nanoparticles provided similar results to control (saline-treated) group of animals. In conclusion, the evaluation of time-to-onset of symptoms and the severity of neurodegenerative processes induced by the tacrine–lithium model of epilepsy in the rat, could be used to evaluate preliminarily the capability of a drug delivery system to trespass (or not) the BBB in vivo.     

Reactive oxygen species generation by copper(II) oxide nanoparticles determined by DNA damage assays and EPR spectroscopy

Copper(II) oxide nanoparticles (^NPCuO) have many industrial applications, but are highly cytotoxic because they generate reactive oxygen species (ROS). It is unknown whether the damaging ROS are generated primarily from copper leached from the nanoparticles, or whether the nanoparticle surface plays a significant role. To address this question, we separated nanoparticles from the supernatant containing dissolved copper, and measured their ability to damage plasmid DNA with addition of hydrogen peroxide, ascorbate, or both. While DNA damage from the supernatant (measured using an electrophoresis assay) can be explained solely by dissolved copper ions, damage by the nanoparticles in the presence of ascorbate is an order of magnitude higher than can be explained by dissolved copper and must, therefore, depend primarily upon the nanoparticle surface. DNA damage is time-dependent, with shorter incubation times resulting in higher EC₅₀ values. Hydroxyl radical (^?OH) is the main ROS generated by ^NPCuO/hydrogen peroxide as determined by EPR measurements; ^NPCuO/hydrogen peroxide/ascorbate conditions generate ascorbyl, hydroxyl, and superoxide radicals. Thus, ^NPCuO generate ROS through several mechanisms, likely including Fenton-like and Haber-Weiss reactions from the surface or dissolved copper ions. The same radical species were observed when ^NPCuO suspensions were replaced with the supernatant containing leached copper, washed ^NPCuO, or dissolved copper solutions. Overall, ^NPCuO generate significantly more ROS and DNA damage in the presence of ascorbate than can be explained simply from dissolved copper, and the ^NPCuO surface must play a large role.     

Cyrene™ as an Alternative Sustainable Solvent for the Preparation of Poly(lactic-co-glycolic acid) Nanoparticles

Toxic and environmental harmful organic solvents are widely applied to prepare poly(lactic-co-glycolic acid) (PLGA)-based nanoparticles (NP) in standard preparation methods. Alternative non-toxic solvents suffer from disadvantages like high viscosity and plasticizing effects. To overcome these hurdles, Cyrene? as a new sustainable, non-toxic and low viscous solvent was used to formulate PLGA NPs. A new preparation method was developed and optimized. Small sized blank NPs around 220 nm with a narrow size distribution and highly negative charge (<?23 mV) were obtained. To test the application for drug delivery, the lipophilic model drug atorvastatin was encapsulated in high drug loads with comparable physicochemical characteristics as the blank NPs, and a total drug release within 24 h. No changes of the crystallinity or plasticizing effects could be observed. Highly purified NPs were obtained with a residual Cyrene? content <2.5%. Finally, the biocompatibility of Cyrene? itself and of the NPs formed in the presence of Cyrene? was demonstrated in a hen's egg test. Conclusively, the use of Cyrene? as solvent offers a simple, fast and non-toxic procedure for preparation of PLGA NPs as drug delivery systems circumventing the downsides of standard methods.     

Are nanoparticles potential male reproductive toxicants? A literature review

The rapid advancement of nanotechnology has prompted the need to investigate the health effects of nanoparticles and nanomaterials. The current focus of health and safety investigations has targeted routes of exposure and potential deposition, translocation, and adverse effects in primary and major secondary target organs. Few studies have looked at deposition in reproductive organs, and even fewer have assessed potential adverse effects on germline cells. This review summarizes the current published research on deposition/translocation of nanoparticles to the testes and male germline cells, and the potential cytotoxic effects. Six research articles were identified. Three articles pertained to deposition/translocation of nanoparticles in the testes, two pertained to cytotoxicity of nanoparticles on male germline cells, and one study assessed deposition and bioaccumulation of nanoparticles in the testes, and potential for adverse reproductive outcomes in successive offspring. While research into the potential reproductive toxicity of nanoparticles is still in its infancy, the identified research suggests that nanoparticles cross the blood testes barrier and deposit in the testes, and that there is potential for adverse effects on sperm cells. Suggestions for future research strategies are outlined.     

二氢卟酚纳米光敏剂对CAL-27细胞的光动力杀伤效应

目的:研究新合成的超支化聚醚酯-二氢卟酚e6纳米光敏剂[hyperbranched poly(ether-ester)-Chlorin e6 nano-photosensitizer,HPEE-ce6]的体外光动力疗法(photodynamic therapy,PDT)对人舌癌CAL-27细胞(human oral tonguecancer CAL-27 cells)的杀伤作用。方法:合成HPEE-ce6后,通过激光共聚焦显微镜观察CAL-27细胞对HPEE-ce6的内摄作用。以游离二氢卟酚e6(Chlorin e6,ce6)为对照组,CAL-27细胞经激光PDT处理(630 nm连续激光照射,功率密度100 mW/cm2、能量密度12 J/cm2、光照600 s),继续孵育细胞24h后,应用MTT法检测HPEE-ce6对CAL-27细胞的光动力杀伤效率。采用SAS 6.12软件包对数据进行统计学处理。结果:HPEE和ce6共价结合,生成直径为50 nm左右的纳米粒子,HPEE-ce6以胞吞方式进入细胞,主要分布于细胞质内。MTT比色法表明,HPEE-ce6对CAL-27细胞的PDT杀伤作用显著强于ce6(P<0.05)。结论:HPEE-ce6对CAL-27细胞具有良好的光动力杀伤作用,且PDT杀伤效率高于ce6。     

酸敏性葡聚糖纳米凝胶的制备与释药性质考察

目的制备具有酸敏特性的聚（甲基丙烯酸缩水甘油酯修饰葡聚糖,dex GMA）/（丙烯酸,AAc）纳米凝胶,研究其降解和释药性质。方法乳液聚合法制备poly(dex GMA/AAc)纳米凝胶,测定不同pH值下的粒度分布,以红霉素（EM）为药物模型,动态透析法测定纳米凝胶在不同pH值下的释药性质。结果poly(dex GMA/AAc)纳米凝胶的平均粒径约为100 nm,包裹率、载药率分别为90.7%和1.06%。在无酶人工胃液 (SGF) 2 h纳米凝胶的药物累积释放率分别为7.0%,之后在无酶人工肠液(SIF)里4 h 内增加到37.0%。结论poly(dex GMA/AAc)纳米凝胶具有酸敏特性,在SGF里释放少量药物,在SIF里凝胶溶胀、降解,药物释放量明显增大。poly(dex GMA/AAc)纳米凝胶是潜在的结肠靶向载体。     

甘草次酸丙烯酸树脂纳米粒的制备及其体外评价

目的:制备和评价甘草次酸丙烯酸树脂E100纳米粒。方法:采用改良乳化-溶剂扩散法制备甘草次酸丙烯酸树脂E100纳米粒,通过考察载体与药物的比例、乳化剂的用量和搅拌速度等对纳米粒径、药物的包封率和载药量的影响,初步筛选处方。动态激光散射法测定粒径,透射电子显微镜观察外观形态。利用透析袋法,在含0.5%SDS的pH溶液中进行体外释放试验。结果:优化处方制备的纳米粒大小均匀,粒径约为(75.0±11.3)nm,包封率为(83.05±5.16)%,载药量为(29.22±1.60)%。甘草次酸的体外释放具有明显的pH依赖性。结论:改良乳化-溶剂扩散法制备了包封率高、大小均匀的pH依赖性甘草次酸纳米粒。     

超临界流体沉降技术在微粒制剂领域的应用最新进展

综述近年来超临界流体沉降技术在药剂学微粒制剂领域的应用研究新进展,其中包括药物微粉化及纳米粒混悬液、微囊和微球的制备.