Comparison of the effect of different chitosan salts and N-trimethyl chitosan chloride on the permeability of intestinal epithelial cells (Caco-2)

Dimethyl Sulfoxide (DMSO) as a Potential Source of Interference in Research Related to Sulfur Metabolism-A Preliminary Study

Dimethyl sulfoxide (DMSO), an organosulfur compound, is widely used as the gold standard solvent in biological research. It is used in cell culture experiments and as a component of formulations in in vivo studies. Unfortunately, parameters related to sulfur metabolism are often not taken into account when using DMSO. Therefore, in this work we aim to show that the addition of DMSO to the culture medium (even in amounts commonly considered acceptable) alters some parameters of sulfur metabolism. For this study, we used three cell lines: a commercially available Caco-2 line (HTB-37, ATCC) and two lines created as part of our early studies (likewise previously described in the literature) to investigate the anomalies of sulfur metabolism in mucopolysaccharidosis. As the negative effects of DMSO on the cell membrane are well known, additional experiments with the partial loading of DMSO into polymerosomes (poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide), PEG-PLGA) were performed to eliminate these potentially disruptive effects. The results show that DMSO is a source of interference in studies related to sulfur metabolism and that there are not just simple effects that can be corrected in the final result by subtracting control values, since complex synergisms are also observed.

Efficacy of oral insulin nanoparticles for the management of hyperglycemia in a rat model of diabetes induced with streptozotocin

Insulin is the cornerstone of treatment in type 1 diabetes mellitus. However, because of its protein structure, insulin has to be administered via injection, and many attempts have been made to create oral formulations, especially using nanoparticles (NPs). The aim of this study was to compare the hypoglycemic effect of insulin-loaded NPs to that of subcutaneous insulin in an in vivo rat model of diabetes. We used biodegradable D-α-tocopherol polyethylene glycol succinate-emulsified, chitosan-capped poly(lactic-co-glycolic acid) NPs loaded with soluble human insulin in a dose of 20 IU/kg body weight, and examined the physical characteristics of NPs in vivo and in vitro. Serum glucose levels were reduced after 6 h, but the difference was not significant compared to subcutaneous insulin; at 12 h and 24 h, insulin levels were significantly higher in rats treated with NPs than in rats treated with subcutaneous insulin. There was no significant difference in serum insulin levels at 12 h and 24 h compared to non-diabetic rats. Our findings suggest that chitosan-based NPs are able to maintain good glycemic control for up to 24 h and can be considered a potential carrier for oral insulin delivery.

Chitosan scaffolds: Expanding horizons in biomedical applications

Chitosan, a natural polysaccharide from chitin, shows promise as a biomaterial for various biomedical applications due to its biocompatibility, biodegradability, antibacterial activity, and ease of modification. This review overviews "chitosan scaffolds" use in diverse biomedical applications. It emphasizes chitosan's structural and biological properties and explores fabrication methods like gelation, electrospinning, and 3D printing, which influence scaffold architecture and mechanical properties. The review focuses on chitosan scaffolds in tissue engineering and regenerative medicine, highlighting their role in bone, cartilage, skin, nerve, and vascular tissue regeneration, supporting cell adhesion, proliferation, and differentiation. Investigations into incorporating bioactive compounds, growth factors, and nanoparticles for improved therapeutic effects are discussed. The review also examines chitosan scaffolds in drug delivery systems, leveraging their prolonged release capabilities and ability to encapsulate medicines for targeted and controlled drug delivery. Moreover, it explores chitosan's antibacterial activity and potential for wound healing and infection management in biomedical contexts. Lastly, the review discusses challenges and future objectives, emphasizing the need for improved scaffold design, mechanical qualities, and understanding of interactions with host tissues. In summary, chitosan scaffolds hold significant potential in various biological applications, and this review underscores their promising role in advancing biomedical science.

Current Advances in Chitosan Nanoparticles Based Oral Drug Delivery for Colorectal Cancer Treatment

As per the WHO, colorectal cancer (CRC) caused around 935,173 deaths worldwide in 2020 in both sexes and at all ages. The available anticancer therapies including chemotherapy, radiotherapy and anticancer drugs are all associated with limited therapeutic efficacy, adverse effects and low chances. This has urged to emerge several novel therapeutic agents as potential therapies for CRC including synthetic and natural materials. Orally administrable and targeted drug delivery systems are attractive strategies for CRC therapy as they minimize the side effects, enhance the efficacy of anticancer drugs. Nevertheless, oral drug delivery till today faces several challenges like poor drug solubility, stability, and permeability. Various oral nano-based approaches and targeted drug delivery systems have been developed recently, as a result of the ability of nanoparticles to control the release of the encapsulant, drug targeting and reduce the number of dosages administered. The unique physicochemical properties of chitosan polymer assist to overcome oral drug delivery barriers and target the colon tumour cells. Chitosan-based nanocarriers offered additional improvements by enhancing the stability, targeting and bioavailability of several anti-colorectal cancer agents. Modified chitosan derivatives also facilitated CRC targeting through strengthening the protection of encapsulant against acidic and enzyme degradation of gastrointestinal track (GIT). This review aims to provide an overview of CRC pathology, therapy and the barriers against oral drug delivery. It also emphasizes the role of nanotechnology in oral drug targeted delivery system and the growing interest towards chitosan and its derivatives. The present review summarizes the relevant works to date that have studied the potential applications of chitosan-based nanocarrier towards CRC treatment.

Evaluation of quaternization effect on chitosan-HAP composite for bone tissue engineering application

This study attempts to improve the aqueous solubility of chitosan and utilizes it in the fabrication of composites with hydroxyapatite (HAP). The composites were evaluated as a curcumin delivery vehicle for bone regeneration. The chitosan was modified by quaternization, with a quaternization degree of 5 % for low quaternized chitosan (LQC) and 11 % for high quaternized chitosan (HQC). The modified chitosan, at alkaline pH 11, facilitated in situ HAP growth and formed LQC-HAP and HQC-HAP composites. The quaternization weakens intermolecular hydrogen bonds, facilitates interaction with the apatite precursor ions and promotes the growth of HAP. The modification significantly improved drug encapsulation (2.6 fold) but at the cost of a slight decrease in mechanical strength and increase in drug release. The in vitro studies with human osteoblast-like MG-63 cells established that the curcumin-loaded composites, LQC-HAP-C and HQC-HAP-C are biocompatible, encourage proliferation and promote a 2-fold increase in calcium mineralization over drug-free composites. The study exemplifies the reciprocity between quaternization degree and drug load/release properties and also illustrates that the magnitude of the latter reflects bioactivity. Thus, the quaternized chitosan-based HAP composite with tailorable bio-physicochemical properties becomes an interesting drug delivery system in bone regeneration.

Chitosan nanoparticles facilitate improved intestinal permeation and oral pharmacokinetics of the mast cell stabiliser cromoglycate

Cromoglycate is a mast cell stabiliser typically administered via inhalation or intranasally for the treatment of allergy-based respiratory issues. Oral dosing of cromoglycate remains challenging due to its high solubility but low permeability across epithelial membranes in the gastrointestinal tract: effective formulation strategies are clearly needed. Here, we investigate and preclinically develop chitosan-cromoglycate complexes and associated nano/microparticle formulations with muco-adhesive and permeation enhancing capabilities to overcome the biopharmaceutical challenges for oral dosing.The synthesized complexes were optimized with respect to chitosan grade, particle size, and drug loading and demonstrated up to a 9.3-fold enhancement in permeability across a Caco-2 monolayer for chitosan-cromoglycate particles, compared to the pure drug. This increased intestinal permeability led to improved pharmacokinetic performance of cromoglycate, e.g. up to 1.82-fold increase in relative oral bioavailability when dosed to Sprague-Dawley rats in a fasted state. These findings confirm the potential for chitosan particles to serve as an effective oral delivery vehicle for cromoglycate, with additional formulation optimization presenting the opportunity to reduce dosing frequency for treatment of allergy-based respiratory ailments.

N-trimethyl chitosan coated nano-complexes enhance the oral bioavailability and chemotherapeutic effects of gemcitabine

N-trimethyl chitosan (TMC) is a multifunctional polymer that can be used in various nanoparticle forms in the pharmaceutical, nutraceutical and biomedical fields. In this study, TMC was used as a mucoadhesive adjuvant to enhance the oral bioavailability and hence antitumour effects of gemcitabine formulated into nanocomplexes composed of poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs) conjugated with d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS). A central composite design was applied to achieve the optimal formulation. Cellular uptake and drug transportation studies revealed the nanocomplexes permeate over the intestinal cells via adsorptive-mediated and caveolae-mediated endocytosis. Pharmacokinetic studies demonstrated the oral drug bioavailability of the nanocomplexes was increased 5.1-fold compared with drug solution. In pharmacodynamic studies, the formulation reduced tumour size 3.1-fold compared with the drug solution. The data demonstrates that TMC modified nanocomplexes can enhance gemcitabine oral bioavailability and promote the anticancer efficacy.

Improved oral delivery of insulin by PLGA nanoparticles coated with 5β-cholanic acid conjugated glycol chitosan

Oral insulin has been regarded as the best alternative to insulin injection in therapy of diabetes because of its convenience and painlessness. However, several obstacles in the gastrointestinal tract, such as gastric acid and enzyme, greatly reduce the bioavailability of oral insulin. Herein, we report design and preparation of poly (d, l-lactic-co-glycolic acid) nanoparticles (PLGA NPs) coated with 5β-cholanic acid modified glycol chitosan (GC-CA) (GC-CA@PLGA NPs) to improve the oral delivery of insulin. The GC-CA@PLGA NPs with the size of (302.73 ± 5.13 nm) and zeta potential of (25.03 ± 0.31 mV) were synthesized using the double-emulsion method. The insulin-loading capacity and encapsulation efficiency were determined to be 5.77 ± 0.58% and 51.99 ± 5.27%, respectively. Compared with GC-modified PLGA NPs (GC@PLGA NPs) and bare PLGA NPs, the GC-CA@PLGA NPs showed excellent stability and uptake by Caco-2 cells after simulated gastric acid digestion. Further experiment suggests good biocompatibility of GC-CA@PLGA NPs, including hemolysis and cytotoxicity. Inin vivoexperiment, the insulin loaded in the GC-CA@PLGA NPs exhibited a long-term and stable release profile for lowering blood glucose and presented 30.43% bioavailability in oral administration. In brief, we have developed an efficient and safe drug delivery system, GC-CA@PLGA NPs, for significantly improved oral administration of insulin, which may find potential application in the treatment of diabetes.

Formulation strategies to improve the efficacy of intestinal permeation enhancers. Adv Drug Deliv Rev 2021;177:113925. [PMID: 34418495 DOI: 10.1016/j.addr.2021.113925]

The use of chemical permeation enhancers (PEs) is the most widely tested approach to improve oral absorption of low permeability active agents, as represented by peptides. Several hundred PEs increase intestinal permeability in preclinical bioassays, yet few have progressed to clinical testing and, of those, only incremental increases in oral bioavailability (BA) have been observed. Still, average BA values of ~1% were sufficient for two recent FDA approvals of semaglutide and octreotide oral formulations. PEs are typically screened in static in vitro and ex-vivo models where co-presentation of active agent and PE in high concentrations allows the PE to alter barrier integrity with sufficient contact time to promote flux across the intestinal epithelium. The capacity to maintain high concentrations of co-presented agents at the epithelium is not reached by standard oral dosage forms in the upper GI tract in vivo due to dilution, interference from luminal components, fast intestinal transit, and possible absorption of the PE per se. The PE-based formulations that have been assessed in clinical trials in either immediate-release or enteric-coated solid dosage forms produce low and variable oral BA due to these uncontrollable physiological factors. For PEs to appreciably increase intestinal permeability from oral dosage forms in vivo, strategies must facilitate co-presentation of PE and active agent at the epithelium for a sustained period at the required concentrations. Focusing on peptides as examples of a macromolecule class, we review physiological impediments to optimal luminal presentation, discuss the efficacy of current PE-based oral dosage forms, and suggest strategies that might be used to improve them.

Current-Driven Organic Electrochemical Transistors for Monitoring Cell Layer Integrity with Enhanced Sensitivity

In this progress report an overview is given on the use of the organic electrochemical transistor (OECT) as a biosensor for impedance sensing of cell layers. The transient OECT current can be used to detect changes in the impedance of the cell layer, as shown by Jimison et al. To circumvent the application of a high gate bias and preventing electrolysis of the electrolyte, in case of small impedance variations, an alternative measuring technique based on an OECT in a current-driven configuration is developed. The ion-sensitivity is larger than 1200 mV V^-1 dec^-1 at low operating voltage. It can be even further enhanced using an OECT based complementary amplifier, which consists of a p-type and an n-type OECT connected in series, as known from digital electronics. The monitoring of cell layer integrity and irreversible disruption of barrier function with the current-driven OECT is demonstrated for an epithelial Caco-2 cell layer, showing the enhanced ion-sensitivity as compared to the standard OECT configuration. As a state-of-the-art application of the current-driven OECT, the in situ monitoring of reversible tight junction modulation under the effect of drug additives, like poly-l-lysine, is discussed. This shows its potential for in vitro and even in vivo toxicological and drug delivery studies.

Characterization of Different Salt Forms of Chitooligosaccharides and Their Effects on Nitric Oxide Secretion by Macrophages

In this paper, chitooligosaccharides in different salt forms, such as chitooligosaccharide lactate, citrate, adipate, etc., were prepared by the microwave method. They were characterized by SEM, FTIR, NMR, etc., and the nitric oxide (NO) expression was determined in RAW 264.7 cells. The results showed that pure chitooligosaccharide was an irregular spherical shape with rough surface, and its different salt type products are amorphous solid with different honeycomb sizes. In addition to the characteristic absorption peaks of chitooligosaccharides, in FTIR, the characteristic absorption of carboxyl group, methylene group, and aromatic group in corresponding acid appeared. The characteristic absorption peaks of carbon in carboxyl group, hydrogen and carbon in methyl, methylene group, and aromatic group in corresponding acid also appeared in NMR. Therefore, the sugar ring structure and linking mode of chitooligosaccharides did not change after salt formation of chitooligosaccharides. Different salt chitooligosaccharides are completely different in promoting NO secretion by macrophages, and pure chitooligosaccharides are the best.

A Review on Chitosan's Uses as Biomaterial: Tissue Engineering, Drug Delivery Systems and Cancer Treatment

Chitosan, derived from chitin, is a biopolymer consisting of arbitrarily distributed β-(1-4)-linked D-glucosamine and N-acetyl-D-glucosamine that exhibits outstanding properties- biocompatibility, biodegradability, non-toxicity, antibacterial activity, the capacity to form films, and chelating of metal ions. Most of these peculiar properties are attributed to the presence of free protonable amino groups along the chitosan backbone, which also gives it solubility in acidic conditions. Moreover, this biopolymer can also be physically modified, thereby presenting a variety of forms to be developed. Consequently, this polysaccharide is used in various fields, such as tissue engineering, drug delivery systems, and cancer treatment. In this sense, this review aims to gather the state-of-the-art concerning this polysaccharide when used as a biomaterial, providing information about its characteristics, chemical modifications, and applications. We present the most relevant and new information about this polysaccharide-based biomaterial's applications in distinct fields and also the ability of chitosan and its various derivatives to selectively permeate through the cancer cell membranes and exhibit anticancer activity, and the possibility of adding several therapeutic metal ions as a strategy to improve the therapeutic potential of this polymer.

Antioxidant and Anti-Inflammatory Properties of Cherry Extract: Nanosystems-Based Strategies to Improve Endothelial Function and Intestinal Absorption

Cherry fruit has a high content in flavonoids. These are important diet components protecting against oxidative stress, inflammation, and endothelial dysfunction, which are all involved in the pathogenesis of atherosclerosis, which is the major cause of cardiovascular diseases (CVD). Since the seasonal availability of fresh fruit is limited, research has been focused on cherry extract (CE), which also possesses a high nutraceutical potential. Many clinical studies have demonstrated the nutraceutical efficacy of fresh cherries, but only a few studies on CE antioxidant and anti-inflammatory activities have been carried out. Here, the results concerning the antioxidant and anti-inflammatory activities of CE are reviewed. These were obtained by an in vitro model based on Human Umbilical Vein Endothelial Cells (HUVEC). To clarify the CE mechanism of action, cells were stressed to induce inflammation and endothelial dysfunction. Considering that antioxidants' polyphenol compounds are easily degraded in the gastrointestinal tract, recent strategies to reduce the degradation and improve the bioavailability of CE are also presented and discussed. In particular, we report on results obtained with nanoparticles (NP) based on chitosan derivatives (Ch-der), which improved the mucoadhesive properties of the chitosan polymers, as well as their positive charge, to favor high cellular interaction and polyphenols intestinal absorption, compared with a non-mucoadhesive negative surface charged poly(lactic-co-glycolic) acid NP. The advantages and safety of different nanosystems loaded with natural CE or other nutraceuticals are also discussed.

Uptake in the Central Nervous System of Geraniol Oil Encapsulated in Chitosan Oleate Following Nasal and Oral Administration

The pharmacological activities of geraniol include anticancer and neuroprotective properties. However, its insolubility in water easily induces separation from aqueous formulations, causing administration difficulties. Here we propose new emulsified formulations of geraniol by using the amphiphilic polymer chitosan-oleate (CS-OA) as surfactant to combine mucoadhesive and absorption enhancer properties with stabilization effects on the oil dispersion. The formulation based on CS-OA 2% (w/w) (G-CS-OA-2.0%) showed viscosity values compatible with oral and nasal administration to rats, and mean diameter of the dispersed phase of 819 ± 104 nm. G-CS-OA-2.0% oral administration sensibly increases the geraniol bioavailability with respect to coarse emulsions obtained without CS-OA (AUC values in the bloodstream were 42,713 ± 1553 µg∙mL⁻¹∙min and 2158 ± 82 µg∙mL⁻¹∙min following administration of 50 mg/kg or 1 mg/kg, respectively), and enhances the aptitude of geraniol to reach the central nervous system from the bloodstream (AUC values in the cerebrospinal fluid were 7293 ± 408 µg∙mL⁻¹∙min and 399 ± 25 µg∙mL⁻¹∙min after oral administration of 50 mg/kg or 1 mg/kg, respectively). Moreover, relevant geraniol amounts were detected in the cerebrospinal fluid following the G-CS-OA-2% nasal administration (AUC values in the cerebrospinal fluid were 10,778 ± 477 µg∙mL⁻¹∙min and 5571 ± 290 µg∙mL⁻¹∙min after nasal administration of 4 mg/kg or 1 mg/kg, respectively).

Potential of chitosan-based carrier for periodontal drug delivery

Periodontal diseases are chronic infectious diseases and are a major oral health burden. With the progress in the understanding of etiology, epidemiology and pathogenesis of periodontal diseases coupled with the understanding of the polymicrobial synergy in the dysbiotic oral microbial flora, several new therapeutic targets have been identified. The strategies to curb bacterial growth and production of factors that gradually destroy the tissue surrounding and supporting the teeth have been the cornerstone for inhibiting periodontitis. Systemic administration of antibiotics for the treatment of periodontitis have shown several drawbacks including: inadequate antibiotic concentration at the site of the periodontal pocket, a rapid decline of the plasma antibiotic concentration to sub-therapeutic levels, the development of microbial resistance due to sub-therapeutic drug levels and peak-plasma antibiotic concentrations which may be associated with various side effects. These obvious disadvantages have evoked an interest in the development of localized drug delivery systems that can provide an effective concentration of antibiotic at the periodontal site for the duration of the treatment with minimal side effects. A targeted sustained release device which could be inserted in the periodontal pocket and prolong the therapeutic levels at the site of action at a much lower dose is the need of the hour. Chitosan, a deacetylated derivative of chitin has attracted considerable attention owing to its special properties including antimicrobial efficacy, biodegradability, biocompatibility and non-toxicity. It also has the propensity to act as hydrating agent and display tissue healing and osteoinducting effect. The aim of this review is to shine a spotlight on the chitosan based devices developed for drug delivery application in the effective treatment of various periodontal disorders. The chitosan based carriers like fibers, films, sponge, microparticles, nanoparticles, gels that have been designed for sustained release of drug into the periodontal pocket are highlighted.

Intestinal Drug Absorption Enhancement by Aloe vera Gel and Whole Leaf Extract: In Vitro Investigations into the Mechanisms of Action

The co-administration of absorption enhancing agents with macromolecular drugs (e.g., protein and peptide drugs) has been identified as a means to improve the oral bioavailability of these drugs. Absorption-enhancing agents of natural origins have received a great deal of attention due to their sustainable production, in support of green chemistry. In previous studies, certain parts of the Aloe vera leaf (e.g., gel and whole leaf extract) have shown a potential to enhance drug permeation across the intestinal epithelial barrier. The mechanism of the drug-absorption-enhancement action and the capacity for absorption-enhancement of the A. vera gel and whole leaf, were investigated in this study. A clear decrease in transepithelial electrical resistance (TEER) of Caco-2 cell monolayers exposed to A. vera gel and wholeleaf extract, in various concentrations, indicated the opening of tight junctions between the epithelial cells. The transport of Fluorescein isothiocyanate (FITC)-dextran, with a molecular weight of 4 kDa (FD-4), could be enhanced across the Caco-2 cell monolayers, by the A. vera gel and whole-leaf extract, but not the FITC-dextran with larger molecular weights (i.e., 10, 20, and 40 kDa), which indicated a limited drug absorption enhancement capacity, in terms of the molecular size. Accumulation of FD-4 between the Caco-2 cells (and not within the cells), after treatment with the A. vera gel and whole-leaf extract was shown with a confocal laser scanning microscopy (CLSM) imaging, indicating that the paracellular transport of FD-4 occurred after the interaction of the A. vera gel and whole-leaf extract, with the epithelial cell monolayers. Furthermore, changes in the F-actin distribution in the cytoskeleton of the Caco-2 cell monolayers was observed by means of a fluorescence staining, which confirmed tight junction modulation as the mechanism of action for the absorption enhancement effect of the A. vera gel and whole-leaf extract.

Drug Bioavailability Enhancing Agents of Natural Origin (Bioenhancers) that Modulate Drug Membrane Permeation and Pre-Systemic Metabolism

Many new chemical entities are discovered with high therapeutic potential, however, many of these compounds exhibit unfavorable pharmacokinetic properties due to poor solubility and/or poor membrane permeation characteristics. The latter is mainly due to the lipid-like barrier imposed by epithelial mucosal layers, which have to be crossed by drug molecules in order to exert a therapeutic effect. Another barrier is the pre-systemic metabolic degradation of drug molecules, mainly by cytochrome P450 enzymes located in the intestinal enterocytes and liver hepatocytes. Although the nasal, buccal and pulmonary routes of administration avoid the first-pass effect, they are still dependent on absorption of drug molecules across the mucosal surfaces to achieve systemic drug delivery. Bioenhancers (drug absorption enhancers of natural origin) have been identified that can increase the quantity of unchanged drug that appears in the systemic blood circulation by means of modulating membrane permeation and/or pre-systemic metabolism. The aim of this paper is to provide an overview of natural bioenhancers and their main mechanisms of action for the nasal, buccal, pulmonary and oral routes of drug administration. Poorly bioavailable drugs such as large, hydrophilic therapeutics are often administered by injections. Bioenhancers may potentially be used to benefit patients by making systemic delivery of these poorly bioavailable drugs possible via alternative routes of administration (i.e., oral, nasal, buccal or pulmonary routes of administration) and may also reduce dosages of small molecular drugs and thereby reduce treatment costs.

Targeted thrombolysis by using c-RGD-modified N,N,N-Trimethyl Chitosan nanoparticles loaded with lumbrokinase

Lumbrokinase (LK) has strong fibrinolytic and thrombolytic activities, but it has a short half-life, can be easily inactivated, and may cause hemorrhage as a side effect. This study develops a potential thrombolytic therapy by fabricating N,N,N-Trimethyl Chitosan (TMC) nanoparticles modified with the cyclic Arg-Gly-Asp-Phe-Lys peptide (c-RGD) and loaded with LK (i.e. c-RGD-LK-NPs). The binding of c-RGD to platelet membrane GPIIb/IIIa receptors is expected to enable targeted delivery of the c-RGD-conjugated TMC to the thrombus. The synthesized c-RGD-LK-NPs had a mean particle size of 232.0 nm, zeta potential of 19.8 mV, entrapment efficiency of 52.7% ± 2.5%, and loading efficiency of 17.4% ± 0.65%. Transmission electron microscopy showed that they were generally spherical. The c-RGD-LK-NPs gave a cumulative in vitro LK release of 80.6% over 8 h, and the activity of LK was close to 80%, indicating that the nanoparticles protected the activity of LK. In vitro blood clot lysis assays were carried out and in vivo thrombolysis effect was tested in Sprague-Dawley rats carotid artery thrombus model. In all cases, the c-RGD-LK-NPs showed superior performance compared with the free LK and the unmodified TMC nanoparticles loaded with LK. The c-RGD-LK-NPs reagent is expected to be potentially useful in treating thromboembolic diseases.

Protoporphyrin IX-modified chitosan-g-oligo(NiPAAm) polymeric micelles: from physical stabilization to permeability characterization in vitro

Two main hurdles persist towards the more extensive bench-to-bed side translation of non-parenteral polymeric micelles. The first pertains to their thermodynamically-driven disassembly under uncontrolled dilution conditions in the biological milieu and upon interaction with biomacromolecules (e.g., proteins). The second is related to the relatively poor understanding of the pathways by which polymeric micelles improve the bioavailability of the payload by mucosal routes (e.g., intestinal). In this work, a chitosan-g-oligo(N-isopropylacrylamide) (CS-g-oligo(NiPAAm)) copolymer was modified with non-cytotoxic amounts of protoporphyrin IX (PP), a planar molecule of amphiphilic character that undergoes self-aggregation in water by forming π-π stacked supramolecular structures, to induce micellization under disfavored conditions and to serve as a fluorescent tracer for the measurement of the micelle permeability across a model of the intestinal epithelium in vitro. Findings indicated that the conjugation of PP amounts as low as 2% w/w induced the formation of micelles at temperatures below the lower critical solution temperature of oligo(NiPAAm) (30-32 °C). Moreover, permeability studies conducted at both 4 °C and 37 °C strongly suggested that despite the relatively large size of the micelles (200-300 nm), they cross the epithelial monolayer mainly by a paracellular pathway due to the opening of tight junctions. Complementary uptake studies by flow cytometry indicated that no endocytosis, though due to passive or facilitated diffusion, some internalization takes place.

Enhancement of drug permeability across blood brain barrier using nanoparticles in meningitis

The central nervous system, one of the most delicate microenvironments of the body, is protected by the blood-brain barrier regulating its homeostasis. Blood-brain barrier is a highly complex structure that tightly regulates the movement of ions of a limited number of small molecules and of an even more restricted number of macromolecules from the blood to the brain, protecting it from injuries and diseases. However, the blood-brain barrier also significantly precludes the delivery of drugs to the brain, thus, preventing the therapy of a number of neurological disorders. As a consequence, several strategies are currently being sought after to enhance the delivery of drugs across the blood-brain barrier. Within this review a brief description of the structural and physiological features of the barriers and the recently born strategy of brain drug delivery based on the use of nanoparticles are described. Finally, the future technological approaches are described. The strong efforts to allow the translation from preclinical to concrete clinical applications are worth the economic investments.

The Effect of Commonly Used Excipients on the Epithelial Integrity of Human Cervicovaginal Tissue

Pharmaceutical excipients are widely used in vaginal drug products. The epithelial integrity of the cervicovaginal tissue is important for HIV-1 prevention. However, the effects of excipients on cervicovaginal epithelium remain unknown. This study aims at assessing the effects of vaginal product excipients on the integrity of human cervicovaginal epithelium and on a lead HIV prevention antiretroviral drug, tenofovir (TFV). In the current study, nine excipients commonly used in vaginal formulations were incubated for 6 h with excised human ectocervical tissue. The effects of the excipients were examined by measuring the transepithelial electrical resistance (TEER), epithelial morphology, paracellular/transcellular permeability, and cell viability. The efficacy of TFV for preventing HIV-1 infection in the ex vivo cultured ectocervix was also tested. We found that disodium ethyl-enediaminetetraacetate (EDTA), sorbic acid, and benzoic acid had no effect on the tissue TEER. Butylated hydroxyanisole, glycerin, propylene glycol, methylparaben, and propylparaben slightly to moderately decreased tissue TEER, whereas citric acid significantly decreased the TEER in a time-dependent manner. Tissue morphology observed post-exposure strongly correlated with TEER data; however, a less strong correlation was observed between paracellular permeability and TEER data after exposure to different excipients. In addition, treatment with EDTA, methylparaben, and propylene glycol at tested levels had no effect on the efficacy of TFV in preventing tissue HIV-1 infection. In conclusion, the combined measurements of TEER, morphology, permeability, and viability using human cervicovaginal tissue represent a clinically relevant platform for safety evaluation of excipients and formulated products for HIV-1 prevention.

The efficiency and mechanism of N-octyl-O, N-carboxymethyl chitosan-based micelles to enhance the oral absorption of silybin

This study demonstrates the preparation of a silybin-loaded N-octyl-O, N-carboxymethyl chitosan micelle (OCC-SLB) to enhance the oral absorption efficiency of silybin (SLB) and investigate the related mechanisms of enhancement. Firstly, the physicochemical properties of OCC and OCC-SLB micelles, including critical micelle concentration (CMC), particle size, zeta potential, drug-loading, etc., were determined. Results of pharmacokinetic studies on rats then confirmed a desirable enhancement in the oral bioavailability of SLB by OCC-SLB micelles compared with a stock SLB suspension solution. Subsequently, uptake studies on the Caco-2 cell line demonstrated that OCC-SLB micelles effectively accumulated SLB or rhodamine-123 into cells through clathrin and caveolae-mediated endocytosis and the inhibition of P-glycoprotein (P-gp) efflux. In addition, results of the Caco-2 transport study further clarified that OCC-SLB micelles enhanced the permeability of SLB via tight junction opening and clathrin-mediated transcytosis across the endothelium. These findings indicated the OCC micelle platform as a potential delivery vehicle for oral administration of P-gp substrates such as SLB.

In-vitro and in-vivo cytotoxicity and efficacy evaluation of novel glycyl-glycine and alanyl-alanine conjugates of chitosan and trimethyl chitosan nano-particles as carriers for oral insulin delivery

PURPOSE

The aim of this research work was to explore the possibility of providing multifunctional oral insulin delivery system by conjugating several types of dipeptides on chitosan and trimethyl chitosan to be used as drug carriers.

METHOD

Conjugates of Glycyl-glycine and alanyl-alanine of chitosan and trimethyl chitosan (on primary alcohol group of polymer located on carbon 6) were synthesized and nanoparticles containing insulin were prepared for oral delivery. Preparation conditions of nanoparticles were optimized and their performance to enhance the permeability of insulin as well as cytotoxicity of nanoparticles in Caco-2 cell line was evaluated. To evaluate the efficacy of orally administered nanoparticles, nanoparticles with the most permeability enhancing ability were studied in male Wistar rats as animal model by measuring insulin and glucose Serum levels.

RESULT

Structural study of all the conjugates by infrared spectroscopy and nuclear magnetic resonance confirmed the successful formation of the conjugates with the desirable substitution degree. By optimizing preparation conditions, nanoparticles with expected size (157.3-197.7 nm), Zeta potential (24.35-34.37 mV), polydispersity index (0.365-0.512), entrapment efficiency (70.60-86.52%) and loading capacity (30.92-56.81%), proper morphology and desirable release pattern were obtained. Glycyl-glycine and alanyl-alanine conjugate nanoparticles of trimethyl chitosan showed 2.5-3.3 folds more effective insulin permeability in Caco-2 cell line than their chitosan counterparts. In animal model, oral administration of glycyl-glycine and alanyl-alanine conjugate nanoparticles of trimethyl chitosan demonstrated reasonable increase in Serum insulin level with relative bioavailability of 17.19% and 15.46% for glycyl-glycine and alanyl-alanine conjugate nanoparticles, respectively, and reduction in Serum glucose level compared with trimethyl chitosan nanoparticles (p < 0.05).

CONCLUSION

It seems that glycyl-glycine and alanyl-alanine conjugate nanoparticles of trimethyl chitosan have met the aim of this research work and have been able to orally deliver insulin with more than one mechanism in animal model. Hence, they are promising candidates for further research studies.

Chitosan hydrochloride has no detrimental effect on bladder urothelial cancer cells

Bladder cancer is among the most common and aggressive human malignant carcinomas, thus targeting and removal of bladder cancer cells is still a challenge. Although it is well known that chitosan hydrochloride (CH-HCl) causes desquamation of normal urothelial cells, its effect on cancer urothelial cells has not been recognized yet. In this in vitro study, we analyzed the cytotoxicity of 0.05% CH-HCl on three urothelial models: two cancer urothelial models, i.e. invasive and papillary urothelial neoplasms, and a normal urothelial model. The cytotoxicity of CH-HCl was evaluated with viability tests, transepithelial resistance (TER) measurements, and electron microscopy. TER measurements showed that 15-minute treatment with CH-HCl caused no reduction in TER of the cancer models, whereas the TER of the normal urothelial model significantly decreased. Furthermore, after CH-HCl treatment, the viability of cancer cells was reduced by only 5%, whereas the viability of normal cells was reduced by 30%. Ultrastructural analysis revealed necrotic cell death in all cases. We have demonstrated that although CH-HCl increases the mortality of cancer urothelial cells, it increases the mortality of normal urothelial cells even more so. However, shorter 2-minute CH-HCl treatment only temporarily increases the permeability of normal urothelial model, i.e. disrupts tight junctions and reduces TER without comprising cell viability, and enables the complete recovery of the permeability barrier after 24h. Overall, our results suggest that CH-HCl cannot be used as a self-sufficient anticancer agent for urothelial bladder cancer treatment; nevertheless a possibility of its use as an enhancer of cytostatic treatment is discussed.

Immunization with Recombinant TcdB-Encapsulated Nanocomplex Induces Protection against Clostridium difficile Challenge in a Mouse Model

Clostridium difficile is considered to be one of the major cause of infectious diarrhea in healthcare systems worldwide. Symptoms of C. difficile infection are caused largely by the production of two cytotoxins: toxin A (TcdA) and toxin B (TcdB). Vaccine development is considered desirable as it would decrease the mounting medical costs and mortality associated with C. difficile infections. Biodegradable nanoparticles composed of poly-γ-glutamic acid (γ-PGA) and chitosan have proven to be a safe and effective antigen delivery system for many viral vaccines. However, few studies have used this efficient antigen carrier for bacterial vaccine development. In this study, we eliminated the toxin activity domain of toxin B by constructing a recombinant protein rTcdB consists of residues 1852-2363 of TcdB receptor binding domain. The rTcdB was encapsulated in nanoparticles composed of γ-PGA and chitosan. Three rounds of intraperitoneal vaccination led to high anti-TcdB antibody responses and afforded mice full protection mice from lethal dose of C. difficile spore challenge. Protection was associated with high levels of toxin-neutralizing antibodies, and the rTcdB-encapsulated NPs elicited a longer-lasting antibody titers than antigen with the conventional adjuvant, aluminum hydroxide. Significant reductions in the level of proinflammatory cytokines and chemokines were observed in vaccinated mouse. These results suggested that polymeric nanocomplex-based vaccine design can be useful in developing vaccine against C. difficile infections.

A novel nanoemulsion-based method to produce ultrasmall, water-dispersible nanoparticles from chitosan, surface modified with cell-penetrating peptide for oral delivery of proteins and peptides

A simple and reproducible water-in-oil (W/O) nanoemulsion technique for making ultrasmall (<15 nm), monodispersed and water-dispersible nanoparticles (NPs) from chitosan (CS) is reported. The nano-sized (50 nm) water pools of the W/O nanoemulsion serve as “nano-containers and nano-reactors”. The entrapped polymer chains of CS inside these “nano-reactors” are covalently cross-linked with the chains of polyethylene glycol (PEG), leading to rigidification and formation of NPs. These NPs possess excessive swelling properties in aqueous medium and preserve integrity in all pH ranges due to chemical cross-linking with PEG. A potent and newly developed cell-penetrating peptide (CPP) is further chemically conjugated to the surface of the NPs, leading to development of a novel peptide-conjugated derivative of CS with profound tight-junction opening properties. The CPP-conjugated NPs can easily be loaded with almost all kinds of proteins, peptides and nucleotides for oral delivery applications. Feasibility of this nanoparticulate system for oral delivery of a model peptide (insulin) is investigated in Caco-2 cell line. The cell culture results for translocation of insulin across the cell monolayer are very promising (15%–19% increase), and animal studies are actively under progress and will be published separately.

Chitosan-coated mesoporous MIL-100(Fe) nanoparticles as improved bio-compatible oral nanocarriers

Nanometric biocompatible Metal-Organic Frameworks (nanoMOFs) are promising candidates for drug delivery. Up to now, most studies have targeted the intravenous route, related to pain and severe complications; whereas nanoMOFs for oral administration, a commonly used non-invasive and simpler route, remains however unexplored. We propose here the biofriendly preparation of a suitable oral nanocarrier based on the benchmarked biocompatible mesoporous iron(III) trimesate nanoparticles coated with the bioadhesive polysaccharide chitosan (CS). This method does not hamper the textural/structural properties and the sorption/release abilities of the nanoMOFs upon surface engineering. The interaction between the CS and the nanoparticles has been characterized through a combination of high resolution soft X-ray absorption and computing simulation, while the positive impact of the coating on the colloidal and chemical stability under oral simulated conditions is here demonstrated. Finally, the intestinal barrier bypass capability and biocompatibility of CS-coated nanoMOF have been assessed in vitro, leading to an increased intestinal permeability with respect to the non-coated material, maintaining an optimal biocompatibility. In conclusion, the preservation of the interesting physicochemical features of the CS-coated nanoMOF and their adapted colloidal stability and progressive biodegradation, together with their improved intestinal barrier bypass, make these nanoparticles a promising oral nanocarrier.

Intestinal permeation enhancers for oral peptide delivery

Intestinal permeation enhancers (PEs) are one of the most widely tested strategies to improve oral delivery of therapeutic peptides. This article assesses the intestinal permeation enhancement action of over 250 PEs that have been tested in intestinal delivery models. In depth analysis of pre-clinical data is presented for PEs as components of proprietary delivery systems that have progressed to clinical trials. Given the importance of co-presentation of sufficiently high concentrations of PE and peptide at the small intestinal epithelium, there is an emphasis on studies where PEs have been formulated with poorly permeable molecules in solid dosage forms and lipoidal dispersions.

New insights into the nature of the Cibacron brilliant red 3B-A – Chitosan interaction

Cibacron brilliant red 3B-A (CBR) has been introduced to determine chitosan (CS) concentrations in solution, and several studies applied it to measure chitosan content in pharmaceutical formulations. So far, studies have relied on the absorbance band shift to 570 nm to determine the extent of the CBR – CS interaction. In this study, we show that CBR forms micro- to nanometer sized aggregates with CS, depending on their charge ratio and that other photophysical changes in CBR are induced by this interaction. We found that, besides the bathochromic band shift, aggregation induces emission at 600 nm and emission quenching at 360 nm. We compared changes CS induced in absorbance and fluorescence emission of CBR with the CS monomer glucosamine and poly(allylamine) hydrochloride, which both contain amino groups, and found that similar but less intense photophysical changes also occur. Furthermore, CS-induced circular dichroism in CBR suggests a twisted, chiral structure of these aggregates that should match with the previously published in silico simulations of the structure of CS in solution. The low linear charge density of CS and its chiral conformation are considered responsible for the enhanced photophysical response of CBR interacting with the polycation.

Low Dosage of Chitosan Supplementation Improves Intestinal Permeability and Impairs Barrier Function in Mice

The purpose of this study was to explore relationships between low dose dietary supplementation with chitosan (COS) and body weight, feed intake, intestinal barrier function, and permeability in mice. Twenty mice were randomly assigned to receive an unadulterated control diet (control group) or a dietary supplementation with 30 mg/kg dose of chitosan (COS group) for two weeks. Whilst no significant differences were found between the conditions for body weight or food and water intake, mice in the COS group had an increased serum D-lactate content (P < 0.05) and a decreased jejunal diamine oxidase (DAO) activity (P < 0.05). Furthermore, mice in COS group displayed a reduced expression of occludin and ZO-1 (P < 0.05) and a reduced expression of occludin in the ileum (P < 0.05). The conclusion drawn from these findings showed that although 30 mg/kg COS-supplemented diet had no effect on body weight or feed intake in mice, this dosage may compromise intestinal barrier function and permeability. This research will contribute to the guidance on COS supplements.

Influence of Surface Chemistry of Poly(Amidoamine) Dendrimers on Caco-2 Cell Monolayers

The objective of this research was to investigate the effect of surface charge of poly(amidoamine), PAMAM, dendrimers on the integrity, paracellular permeability, and viability of Caco-2 cell monolayers by monitoring the transepithelial electrical resistance (TEER), mannitol permeability, and leakage of lactate dehydrogenase (LDH) enzyme, respectively. Neutral PAMAMOH, generations 2-4 (G2-G4), and anionic PAMAM-COOH (G-0.5-G4.5) dendrimers were incubated with Caco-2 cell monolayers at donor concentrations of 0.1, 1.0, and 10.0 mM for 90, 150, and 210 min. Neutral G2-G4 and anionic G-0.5, G0.5, G1.5 and G4.5 dendrimers did not cause any significant change in TEER or mannitol permeability across Caco-2 cell monolayers. Anionic G2.5 and G3.5 dendrimers, however, caused an incubation time-dependant decline in TEER values and up to a 6-fold increase in mannitol permeability. All anionic PAMAM-COOH dendrimers caused an incubation time-, concentration-, and generation-dependant LDH leakage that was not observed with neutral PAMAM-OH dendrimers. These studies suggest a size and/or charge “window” where anionic dendrimers may enhance paracellular transport across Caco-2 cell monolayers further confirming their potential as drug carriers and permeation enhancers for oral drug delivery.

Spray Dried Chitosan Microparticles for Intravesical Delivery of Celecoxib: Preparation and Characterization

PURPOSE

Chitosan microparticles containing celecoxib (CB), were developed as chemoprevention of bladder cancer. Furthermore two inclusion complexes of CB with methyl-β-cyclodextrin (C1 and C2) were prepared to improve the solubility of the drug.

METHODS

C1 and C2 were obtained by freeze-drying and characterized in the solid state and in solution. Microparticles loaded with CB or C1 or C2 were prepared by spray drying and fully characterized.

RESULTS

The yield and encapsulation efficiencies of microparticles depended by both the viscosity and the presence of the inclusion complex in the feed medium nebulised. Generally, the microparticles exhibited a spherical shape with mean diameter of approximately 2 μm which was compatible with local intravesical administration using a catheter. The CB release studies from the microparticles allowed us to identify both immediate release systems (microparticles including the complexes) and prolonged release systems (microparticles including CB alone). The latter exhibited good adhesion to the bladder mucosa, as highlighted by a mucoadhesion study. Histological studies revealed a desquamation of the superficial cells when the bladder mucosa was treated with microparticles loaded with CB, while the morphology of the urothelium did not change when it was treated with microparticles loaded with the inclusion complex.

CONCLUSION

A new CB intravesical formulation than can easily be administered with a catheter and is able to release the drug at the target site for several hours was realized. This new delivery system could be a good alternative to classic oral CB administration.

Manufacturing Techniques and Surface Engineering of Polymer Based Nanoparticles for Targeted Drug Delivery to Cancer

The evolution of polymer based nanoparticles as a drug delivery carrier via pharmaceutical nano/microencapsulation has greatly promoted the development of nano- and micro-medicine in the past few decades. Poly(lactide-co-glycolide) (PLGA) and chitosan, which are biodegradable and biocompatible polymers, have been approved by both the Food & Drug Administration (FDA) and European Medicine Agency (EMA), making them ideal biomaterials that can be advanced from laboratory development to clinical oral and parental administrations. PLGA and chitosan encapsulated nanoparticles (NPs) have successfully been developed as new oral drug delivery systems with demonstrated high efficacy. This review aims to provide a comprehensive overview of the fabrication of PLGA and chitosan particulate systems using nano/microencapsulation methods, the current progress and the future outlooks of the nanoparticulate drug delivery systems. Especially, we focus on the formulations and nano/micro-encapsulation techniques using top-down techniques. It also addresses how the different phases including the organic and aqueous ones in the emulsion system interact with each other and subsequently influence the properties of the drug delivery system. Besides, surface modification strategies which can effectively engineer intrinsic physicochemical properties are summarised. Finally, future perspectives and potential directions of PLGA and chitosan nano/microencapsulated drug systems are outlined.

Nanoparticle based insulin delivery system: the next generation efficient therapy for Type 1 diabetes

Diabetic cases have increased rapidly in recent years throughout the world. Currently, for type-1 diabetes mellitus (T1DM), multiple daily insulin (MDI) injections is the most popular treatment throughout the world. At this juncture, researchers are trying to develop different insulin delivery systems, especially through oral and pulmonary route using nanocarrier based delivery system. This next generation efficient therapy for T1DM may help to improve the quality of life of diabetic patients who routinely employ insulin by the subcutaneous route. In this paper, we have depicted various next generation nanocarrier based insulin delivery systems such as chitosan-insulin nanoparticles, PLGA-insulin nanoparticles, dextran-insulin nanoparticles, polyalkylcyanoacrylated-insulin nanoparticles and solid lipid-insulin nanoparticles. Modulation of these insulin nanocarriers may lead to successful oral or pulmonary insulin nanoformulations in future clinical settings. Therefore, applications and limitations of these nanoparticles in delivering insulin to the targeted site have been thoroughly discussed.

Chitosan-based mucosal adjuvants: Sunrise on the ocean

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Metabolism and safety profile of chitosan and its derivatives on mucosal application.

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Mechanisms of chitosan as potent mucosal adjuvant.

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Different types and forms of chitosan in pre-clinical applications.

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Clinical perspectives.

Mucosal vaccination, which is shown to elicit systemic and mucosal immune responses, serves as a non-invasive and convenient alternative to parenteral administration, with stronger capability in combatting diseases at the site of entry. The exploration of potent mucosal adjuvants is emerging as a significant area, based on the continued necessity to amplify the immune responses to a wide array of antigens that are poorly immunogenic at the mucosal sites. As one of the inspirations from the ocean, chitosan-based mucosal adjuvants have been developed with unique advantages, such as, ability of mucosal adhesion, distinct trait of opening the junctions to allow the paracellular transport of antigen, good tolerability and biocompatibility, which guaranteed the great potential in capitalizing on their application in human clinical trials. In this review, the state of art of chitosan and its derivatives as mucosal adjuvants, including thermo-sensitive chitosan system as mucosal adjuvant that were newly developed by author's group, was described, as well as the clinical application perspective. After a brief introduction of mucosal adjuvants, chitosan and its derivatives as robust immune potentiator were discussed in detail and depth, in regard to the metabolism, safety profile, mode of actions and preclinical and clinical applications, which may shed light on the massive clinical application of chitosan as mucosal adjuvant.

Development of acid-resistant alginate/trimethyl chitosan nanoparticles containing cationic β-cyclodextrin polymers for insulin oral delivery

In this study, the use of trimethylchitosan (TMC), by higher solubility in comparison with chitosan, in alginate/chitosan nanoparticles containing cationic β-cyclodextrin polymers (CPβCDs) has been studied, with the aim of increasing insulin uptake by nanoparticles. Firstly, TMCs were synthesized by iodomethane, and CPβCDs were synthesized within a one-step polycondensation reaction using choline chloride (CC) and epichlorohydrine (EP). Insulin-CβCDPs complex was prepared by mixing 1:1 portion of insulin and CPβCDs solutions. Then, nanoparticles prepared in a three-step procedure based on the iono-tropic pregelation method. Nanoparticles screened using experimental design and Placket Burman methodology to obtain minimum size and polydispercity index (pdI) and the highest entrapment efficiency (EE). CPβCDs and TMC solution concentration and pH and alginate and calcium chloride solution concentrations are found as the significant parameters on size, PdI, and EE. The nanoparticles with proper physicochemical properties were obtained; the size, PdI, and EE% of optimized nanoparticles were reported as 150.82 ± 21 nm, 0.362 ± 0.036, and 93.2% ± 4.1, respectively. The cumulative insulin release in intestinal condition achieved was 50.2% during 6 h. By SEM imaging, separate, spherical, and nonaggregated nanoparticles were found. In the cytotoxicity studies on Caco-2 cell culture, no significant cytotoxicity was observed in 5 h of incubation, but after 24 h of incubation, viability was decreased to 50% in 0.5 mμ of TMC concentration. Permeability studies across Caco-2 cells had been carried out, and permeability achieved in 240 min was 8.41 ± 0.39%, which shows noticeable increase in comparison with chitosan nanoparticles. Thus, according to the results, the optimized nanoparticles can be used as a new insulin oral delivery system.

N-trimethyl chitosan chloride-coated PLGA nanoparticles overcoming multiple barriers to oral insulin absorption

Although several strategies have been applied for oral insulin delivery to improve insulin bioavailability, little success has been achieved. To overcome multiple barriers to oral insulin absorption simultaneously, insulin-loaded N-trimethyl chitosan chloride (TMC)-coated polylactide-co-glycoside (PLGA) nanoparticles (Ins TMC-PLGA NPs) were formulated in our study. The Ins TMC-PLGA NPs were prepared using the double-emulsion solvent evaporation method and were characterized to determine their size (247.6 ± 7.2 nm), ζ-potential (45.2 ± 4.6 mV), insulin-loading capacity (7.8 ± 0.5%) and encapsulation efficiency (47.0 ± 2.9%). The stability and insulin release of the nanoparticles in enzyme-containing simulated gastrointestinal fluids suggested that the TMC-PLGA NPs could partially protect insulin from enzymatic degradation. Compared with unmodified PLGA NPs, the positively charged TMC-PLGA NPs could improve the mucus penetration of insulin in mucus-secreting HT29-MTX cells, the cellular uptake of insulin via clathrin- or adsorption-mediated endocytosis in Caco-2 cells and the permeation of insulin across a Caco-2 cell monolayer through tight junction opening. After oral administration in mice, the TMC-PLGA NPs moved more slowly through the gastrointestinal tract compared with unmodified PLGA NPs, indicating the mucoadhesive property of the nanoparticles after TMC coating. Additionally, in pharmacological studies in diabetic rats, orally administered Ins TMC-PLGA NPs produced a stronger hypoglycemic effect, with 2-fold higher relative pharmacological availability compared with unmodified NPs. In conclusion, oral insulin absorption is improved by TMC-PLGA NPs with the multiple absorption barriers overcome simultaneously. TMC-PLGA NPs may be a promising drug delivery system for oral administration of macromolecular therapeutics.

Bioactive self-assembling lipid-like peptides as permeation enhancers for oral drug delivery

Amphiphilic, lipid-like, self-assembling peptides are functional biomaterials with surfactant properties. In this work, lipid-like peptides were designed to have a hydrophilic head composed of aspartic acid or lysine and a six alanine residue hydrophobic domain and have a length similar to that of biological lipids. The aim of this work was to examine the potential of using ac-A6 K-CONH2 , KA6 -CONH2 , ac-A6 D-COOH, and DA6 -COOH lipid-like peptides as permeability enhancers to facilitate transport through the intestinal barrier. In vitro transport studies of the macromolecular fluorescent marker fluorescein isothiocyanate (FITC)-dextran (4.4 kDa) through Caco-2 cell monolayers show the permeation enhancement ability of the lipid-like peptides. We observed increased FITC-dextran transport across the epithelial monolayer up to 7.6-fold in the presence of lipid-like peptides. Furthermore, we monitored the transepithelial resistance and performed immunofluorescence studies of the cell tight junctions. Ex vivo studies showed increased mucosal to serosal absorption of FITC-dextran in rat jejunum in the presence of the ac-A6 D-COOH peptide. Furthermore, a small increase in the serosal transport of bovine serum albumin was observed upon addition of ac-A6 D-COOH. Lipid-like peptides are biocompatible and they do not affect epithelial cell viability and epithelial monolayer integrity. Our results suggest that short, lipid-like peptides may be used as permeation enhancers to facilitate oral delivery of diagnostic and therapeutic molecules.

Measuring direct current trans-epithelial electrical resistance in organ-on-a-chip microsystems

Trans-epithelial electrical resistance (TEER) measurements are widely used as real-time, non-destructive, and label-free measurements of epithelial and endothelial barrier function. TEER measurements are ideal for characterizing tissue barrier function in organs-on-chip studies for drug testing and investigation of human disease models; however, published reports using this technique have reported highly conflicting results even with identical cell lines and experimental setups. The differences are even more dramatic when comparing measurements in conventional Transwell systems with those obtained in microfluidic systems. Our goal in this work was therefore to enhance the fidelity of TEER measurements in microfluidic organs-on-chips, specifically using direct current (DC) measurements of TEER, as this is the most widely used method reported in the literature. Here we present a mathematical model that accounts for differences measured in TEER between microfluidic chips and Transwell systems, which arise from differences in device geometry. The model is validated by comparing TEER measurements obtained in a microfluidic gut-on-a-chip device versus in a Transwell culture system. Moreover, we show that even small gaps in cell coverage (e.g., 0.4%) are sufficient to cause a significant (~80%) drop in TEER. Importantly, these findings demonstrate that TEER measurements obtained in microfluidic systems, such as organs-on-chips, require special consideration, specifically when results are to be compared with measurements obtained from Transwell systems.