Pharmaceutical nanoparticles and the mucin biopolymer barrier

Multiresponsive Nanogels for the Selective Delivery of Antimicrobial Drugs to Mucosal Tissues

Effective drug delivery to bacterially infected mucosa remains a challenge due to the combined obstacles of the mucosal barrier, pH variations, and high concentrations of glutathione. However, polysaccharide-based responsive nanogels (NGs) can take advantage of these conditions to deliver specific antimicrobials. We explored the critical features of pH- and redox-responsive NGs to increase drug penetration, residence time, and efficacy in the infected mucosa. We prepared multifunctional NGs using hydroxypropyl cellulose as a template for the cross-linking of methacrylic acid with N,N'-bis(acryloyl)cystamine (BAC) or N,N'-methylenebis(acrylamide) (BIS). Studies of NG-mucin binding and the antibacterial efficacy of doxycycline-loaded NGs revealed the interplay between the response to pH and redox clues. Specifically, higher BAC composition increased mucus binding and controlled release in reductive conditions, while higher BIS composition yielded NGs with higher doxycycline-mediated antibacterial efficacy against Staphylococcus aureus. The findings reveal the potential of multiresponsive NGs in effective antimicrobial delivery in infected mucosa.

Development of Eudragit® Nanoparticles for Intranasal Drug Delivery: Preliminary Technological and Toxicological Evaluation

Intranasal administration has assumed in the last years an increasing value as an alternative strategy for the systemic adsorption of drugs, as an alternative to oral and parenteral routes thanks to the high vascularized nasal mucosa. Nevertheless, different drug features may restrict its absorption through the nasal mucosa with an insufficient diffusion to the systemic circulation. Several technological strategies are under investigation to improve drug absorption during nasal formulation design and production. The use of bioadhesive polymers can be considered a valid approach to pursue the aforementioned goal. Based on this consideration, Eudragit® Retard RS100 and RL100 resins were selected as positively charged copolymers to prepare polymeric NPs with potential mucoadhesive properties suitable for intranasal application. NPs were produced by the Quasi-emulsion Solvent Evaporation (QESD) method and loaded with diclofenac acid (DIC) or its epolamine salt (DIEP). Preliminary investigations were performed to obtain the optimized blank formulation and drugs loaded NPs evaluating different parameters that can affect particles size and polydispersity. The optimized formulations unloaded and loaded with DIC and DIEP were further evaluated for their thermotropic behavior by differential scanning calorimetry. Mucoadhesive evaluation was assessed by measuring variation in zeta potential and by turbidimetric assay after incubation of particles with mucin in simulated nasal fluid (SNF) at 37 °C at different time points (0, 1 and 24 h) compared to the pure suspensions. Stability of DIC and DIEP loaded NPs was also evaluated in SNF to predict potential aggregation phenomena after nasal administration. Finally, in vivo experiments showed absence of toxicity on the nasal mucosa of mice.

Oral 4-(N)-stearoyl gemcitabine nanoparticles inhibit tumor growth in mouse models

In spite of recent advances in targeted tumor therapy, systemic chemotherapy with cytotoxic agents remains a vital cancer treatment modality. Gemcitabine is a nucleoside analog commonly used in the treatment of various solid tumors, but an oral gemcitabine dosage form remain unavailable. Previously, we developed the 4-(N)-stearoyl gemcitabine solid lipid nanoparticles (GemC18-SLNs) by incorporating 4-(N)-stearoyl gemcitabine (GemC18), an amide prodrug of gemcitabine, into solid lipid nanoparticles. GemC18-SLNs, when administered intravenously, showed strong antitumor activity against various human and mouse tumors in mouse models. In the present study, we defined the plasma pharmacokinetics of gemcitabine when GemC18-SLNs were given orally to healthy mice and evaluated the antitumor activity of GemC18-SLNs when given orally in mouse models of lung cancer. In mice orally gavaged with GemC18-SLNs, plasma gemcitabine concentration followed an absorption phase and then clearance phase, with a Tmax of ~2 h. The absolute oral bioavailability of gemcitabine in the GemC18-SLNs was ~70% (based on AUC0-24 h values). In mice with pre-established tumors (i.e. mouse TC-1 or LLC lung cancer cells), oral GemC18-SLNs significantly inhibited the tumor growth and increased mouse survival time, as compared to the molar equivalent dose of gemcitabine hydrochloride or GemC18 in vegetable oil or in Tween 20. Immunohistostaining revealed that oral GemC18-SLNs also have significant antiproliferative, antiangiogenic, and proapoptotic activity in LLC tumors. Formulating a lipophilic amide prodrug of gemcitabine into solid lipid nanoparticles may represent a viable approach toward developing a safe and efficacious gemcitabine oral dosage form.

Oral uptake of nanoparticles: human relevance and the role of in vitro systems

Nanoparticles (NPs) present in environment, consumer and health products, food and medical applications lead to a high degree of human exposure and concerns about potential adverse effects on human health. For the general population, the exposure through contact with the skin, inhalation and oral uptake are most relevant. Since in vivo testing is only partly able to study the effects of human oral exposure, physiologically relevant in vitro systems are being developed. This review compared the three routes taking into account the estimated concentration, size of the exposed area, morphology of the involved barrier and translocation rate. The high amounts of NPs in food, the large absorption area and the relatively high translocation rate identified oral uptake as most important portal of entry for NPs into the body. Changes of NP properties in the physiological fluids, mechanisms to cross mucus and epithelial barrier, and important issues in the use of laboratory animals for oral exposure are mentioned. The ability of in vitro models to address the varying conditions along the oro-gastrointestinal tract is discussed, and requirements for physiologically relevant in vitro testing of orally ingested NPs are listed.

Targeting tumor microenvironment: crossing tumor interstitial fluid by multifunctional nanomedicines

Introduction: The genesis of cancer appears to be a complex matter, which is not simply based upon few genetic abnormalities/alteration. In fact, irregular microvasculature and aberrant interstitium of solid tumors impose significant pathophysiologic barrier functions against cancer treatment modalities, hence novel strategies should holistically target bioelements of tumor microenvironment (TME). In this study, we provide some overview and insights on TME and important strategies used to control the impacts of such pathophysiologic barriers.

Methods: We reviewed all relevant literature for the impacts of tumor interstitium and microvasculature within the TME as well as the significance of the implemented strategies.

Results: While tumorigenesis initiation seems to be in close relation with an emergence of hypoxia and alterations in epigenetic/genetic materials, large panoplies of molecular events emerge as intricate networks during oncogenesis to form unique lenient TME in favor of tumor progression. Within such irregular interstitium, immune system displays defective surveillance functionalities against malignant cells. Solid tumors show multifacial traits with coadaptation and self-regulation potentials, which bestow profound resistance against the currently used conventional chemotherapy and immunotherapy agents that target solely one face of the disease.

Conclusion: The cancerous cells attain unique abilities to form its permissive microenvironment, wherein (a) extracellular pH is dysregulated towards acidification, (b) extracellular matrix (ECM) is deformed, (c) stromal cells are cooperative with cancer cells, (d) immune system mechanisms are defective, (e) non-integrated irregular microvasculature with pores (120-1200 nm) are formed, and (h) interstitial fluid pressure is high. All these phenomena are against cancer treatment modalities. As a result, to control such abnormal pathophysiologic traits, novel cancer therapy strategies need to be devised using multifunctional nanomedicines and theranostics.

Liposomes coated with thiolated chitosan enhance oral peptide delivery to rats

The aim of the present study was the in vivo evaluation of thiomer-coated liposomes for an oral application of peptides. For this purpose, salmon calcitonin was chosen as a model drug and encapsulated within liposomes. Subsequently, the drug loaded liposomes were coated with either chitosan-thioglycolic acid (CS-TGA) or an S-protected version of the same polymer (CS-TGA-MNA), leading to an increase in the particle size of about 500 nm and an increase in the zeta potential from approximately -40 mV to a maximum value of about +44 mV, depending on the polymer. Coated liposomes were demonstrated to effectively penetrate the intestinal mucus layer where they came in close contact with the underlying epithelium. To investigate the permeation enhancing properties of the coated liposomes ex vivo, we monitored the transport of fluoresceinisothiocyanate-labeled salmon calcitonin (FITC-sCT) through rat small intestine. Liposomes coated with CS-TGA-MNA showed the highest effect, leading to a 3.8-fold increase in the uptake of FITC-sCT versus the buffer control. In vivo evaluation of the different formulations was carried out by the oral application of 40 μg of sCT per rat, either encapsulated within uncoated liposomes, CS-TGA-coated liposomes or CS-TGA-MNA-coated liposomes, or given as a solution serving as negative control. The blood calcium level was monitored over a time period of 24h. The highest reduction in the blood calcium level, to a minimum of 65% of the initial value after 6h, was achieved for CS-TGA-MNA-coated liposomes. Comparing the areas above curves (AAC) of the blood calcium levels, CS-TGA-MNA-coated liposomes led to an 8.2-fold increase compared to the free sCT solution if applied orally in the same concentration. According to these results, liposomes coated with S-protected thiomers have demonstrated to be highly valuable carriers for enhancing the oral bioavailability of salmon calcitonin.