Impact of bile salts and a medium chain fatty acid on the physical properties of self-emulsifying drug delivery systems.

The aim of this study was the evaluation of the influence of bile salts and fatty acids, important components of intestinal fluids, on physical characteristics of self-emulsifying drug delivery systems (SEDDS) such as size, polydispersity (PDI), zeta potential (Zp), turbidity (T%), cloud point temperature (CPT) and drug release. At this purpose, nonionic (ni-SEDDS) and cationic (c-SEDDS) were emulsified in aqueous media containing increasing concentrations of bile salts (BS) and decanoate (Dec). Zp of ni-SEDDS and c-SEDDS became highly negative at 15 mM BS and Dec. Size of ni-SEDDS decreased of 112 nm and of 76 nm at 15 mM BS and Dec, respectively. Size of c-SEDDS decreased of 53 nm at 15 mM BS, but it was not affected by 15 mM Dec. PDI and T% of ni- and c-SEDDS were lowered as well. CPT of ni-SEDDS increased from 70 °C to 97 °C and 84 °C at 15 mM BS and Dec. CPT of c-SEDDS decreased from above 100 °C to 80 °C and to 85 °C at 1.5 mM BS and at 5 mM Dec, respectively. Generally, BS had a more pronounced effect on SEDDS Zp, size, PDI, T %, and CPT than Dec. The release of the model drug quinine was accelerated by BS and Dec. As BS and fatty acids affect the physical characteristics and drug release behavior of SEDDS, their impact should be addressed during the development process.

Effects of excipients on the interactions of self-emulsifying drug delivery systems with human blood plasma and plasma membranes.

Due to its versatility in formulation and manufacturing, self-emulsifying drug delivery systems (SEDDS) can be used to design parenteral formulations. Therefore, it is necessary to understand the effects of excipients on the behavior of SEDDS formulations upon parenteral administration, particularly their interactions with blood plasma and cell membranes. In this study, we prepared three neutrally charged SEDDS formulations composed of medium-chain triglycerides as the oil phase, polyoxyl-35 castor oil (EL35) and polyethylene glycol (15)-hydroxystearate (HS15) as the nonionic surfactants, medium-chain mono- and diglycerides as the co-surfactant, and propylene glycol as the co-solvent. The cationic surfactant, didodecyldimethylammonium bromide (DDA), and the anionic surfactant, sodium deoxycholate (DEO), were added to the neutral SEDDS preconcentrates to obtain cationic and anionic SEDDS, respectively. SEDDS were incubated with human blood plasma and recovered by size exclusion chromatography. Data showed that SEDDS emulsion droplets can bind plasma protein to different extents depending on their surface charge and surfactant used. At pH 7.4, the least protein binding was observed with anionic SEDDS. Positive charges increased protein binding. SEDDS stabilized by HS15 can adsorb more plasma protein and induce more plasma membrane disruption activity than SEDDS stabilized by EL35. These effects were more pronounced with the HS15 + DDA combination. The addition of DDA and DEO to SEDDS increased plasma membrane disruption (PMD) activities, and DDA (1% w/w) was more active than DEO (2% w/w). PMD activities of SEDDS were concentration-dependent and vanished at appropriate dilution ratios.

Promotion of Th17 Polarized Immunity via Co-Delivery of Mincle Agonist and Tuberculosis Antigen Using Silica Nanoparticles.

Adjuvants and immunomodulators that effectively drive a Th17-skewed immune response are not part of the standard vaccine toolkit. Vaccine adjuvants and delivery technologies that can induce Th17 or Th1/17 immunity and protection against bacterial pathogens, such as tuberculosis (TB), are urgently needed. Th17-polarized immune response can be induced using agonists that bind and activate C-type lectin receptors (CLRs) such as macrophage inducible C-type lectin (Mincle). A simple but effective strategy was developed for codelivering Mincle agonists with the recombinant Mycobacterium tuberculosis fusion antigen, M72, using tunable silica nanoparticles (SNP). Anionic bare SNP, hydrophobic phenyl-functionalized SNP (P-SNP), and cationic amine-functionalized SNP (A-SNP) of different sizes were coated with three synthetic Mincle agonists, UM-1024, UM-1052, and UM-1098, and evaluated for adjuvant activity in vitro and in vivo. The antigen and adjuvant were coadsorbed onto SNP via electrostatic and hydrophobic interactions, facilitating multivalent display and delivery to antigen presenting cells. The cationic A-SNP showed the highest coloading efficiency for the antigen and adjuvant. In addition, the UM-1098-adsorbed A-SNP formulation demonstrated slow-release kinetics in vitro, excellent stability over 12 months of storage, and strong IL-6 induction from human peripheral blood mononuclear cells. Co-adsorption of UM-1098 and M72 on A-SNP significantly improved antigen-specific humoral and Th17-polarized immune responses in vivo in BALB/c mice relative to the controls. Taken together, A-SNP is a promising platform for codelivery and proper presentation of adjuvants and antigens and provides the basis for their further development as a vaccine delivery platform for immunization against TB or other diseases for which Th17 immunity contributes to protection.

S-Protected Thiolated Chitosan versus Thiolated Chitosan as Cell Adhesive Biomaterials for Tissue Engineering.

Chitosan (Ch) and different Ch derivatives have been applied in tissue engineering (TE) because of their biocompatibility, favored mechanical properties, and cost-effectiveness. Most of them, however, lack cell adhesive properties that are crucial for TE. In this study, we aimed to design an S-protected thiolated Ch derivative exhibiting high cell adhesive properties serving as a scaffold for TE. 3-((2-Acetamido-3-methoxy-3-oxopropyl)dithio) propanoic acid was covalently attached to Ch via a carbodiimide-mediated reaction. Low-, medium-, and high-modified Chs (Ch-SS-1, Ch-SS-2, and Ch-SS-3) with 54, 107 and 140 µmol of ligand per gram of polymer, respectively, were tested. In parallel, three thiolated Chs, namely Ch-SH-1, Ch-SH-2, and Ch-SH-3, were prepared by conjugating N-acetyl cysteine to Ch at the same degree of modification to compare the effectiveness of disulfide versus thiol modification on cell adhesion. Ch-SS-1 showed better cell adhesion capability than Ch-SS-2 and Ch-SS-3. This can be explained by the more lipophilic surfaces of Ch-SS as a higher modification was made. Although Ch-SH-1, Ch-SH-2, and Ch-SH-3 were shown to be good substrates for cell adhesion, growth, and proliferation, Ch-SS polymers were superior to Ch-SH polymers in the formation of 3D cell cultures. Cryogels structured by Ch-SS-1 (SSg) resulted in homogeneous scaffolds with tunable pore size and mechanical properties by changing the mass ratio between Ch-SS-1 and heparin used as a cross-linker. SSg scaffolds possessing interconnected microporous structures showed good cell migration, adhesion, and proliferation. Therefore, Ch-SS can be used to construct tunable cryogel scaffolds that are suitable for 3D cell culture and TE.

Synthesis and evaluation of sulfosuccinate-based surfactants as counterions for hydrophobic ion pairing.

Hydrophobic ion pairing is a promising strategy to raise the lipophilic character of therapeutic peptides and proteins. In past studies, docusate, an all-purpose surfactant with a dialkyl sulfosuccinate structure, showed highest potential as hydrophobic counterion. Being originally not purposed for hydrophobic ion pairing, it is likely still far away from the perfect counterion. Thus, within this study, docusate analogues with various linear and branched alkyl residues were synthesized to derive systematic insights into which hydrophobic tail is most advantageous for hydrophobic ion pairing, as well as to identify lead counterions that form complexes with superior hydrophobicity. The successful synthesis of the target compounds was confirmed by FT-IR, 1H-NMR, and 13C-NMR. In a screening with the model protein hemoglobin, monostearyl sulfosuccinate, dioleyl sulfosuccinate, and bis(isotridecyl) sulfosuccinate were identified as lead counterions. Their potential was further evaluated with the peptides and proteins vancomycin, insulin, and horseradish peroxidase. Dioleyl sulfosuccinate and bis(isotridecyl) sulfosuccinate significantly increased the hydrophobicity of the tested peptides and proteins determined as logP or lipophilicity determined as solubility in 1-octanol, respectively, in comparison to the gold standard docusate. Dioleyl sulfosuccinate provided an up to 8.3-fold higher partition coefficient and up to 26.5-fold higher solubility in 1-octanol than docusate, whereas bis(isotridecyl) sulfosuccinate resulted in an up to 6.7-fold improvement in the partition coefficient and up to 44.0-fold higher solubility in 1-octanol. The conjugation of highly lipophilic alkyl tails to the polar sulfosuccinate head group allows the design of promising counterions for hydrophobic ion pairing. STATEMENT OF SIGNIFICANCE: Hydrophobic ion pairing enables efficient incorporation of hydrophilic molecules into lipid-based formulations by forming complexes with hydrophobic counterions. Docusate, a sulfosuccinate with two branched alkyl tails, has shown highest potential as anionic hydrophobic counterion. As it was originally not purposed for hydrophobic ion pairing, its structure is likely still far away from the perfect counterion. To improve its properties, analogues of docusate with various alkyl tails were synthesized in the present study. The investigation of different alkyl residues allowed to derive systematic insights into which tail structures are most favorable for hydrophobic ion pairing. Moreover, the lead counterions dioleyl sulfosuccinate and bis(isotridecyl) sulfosuccinate bearing highly lipophilic alkyl tails provided a significant improvement in the hydrophobicity of the resulting complexes.

Polyaminated pullulan, a new biodegradable and cationic pullulan derivative for mucosal drug delivery.

AIM: To prepare new polycationic pullulan derivatives exhibiting highly mucoadhesive and sustained drug release properties. METHODS: Hydroxy groups of pullulan were activated with mesyl chloride followed by conjugation with low-molecular weight polyamines. Pullulan-tris(2-aminoethyl)amine (Pul-TAEA) and pullulan-polyethyleneimine (Pul-PEI) were evaluated regarding swelling behaviour, mucoadhesive properties and potential to control drug release. RESULTS: Pul-TAEA and Pul-PEI exhibited excellent swelling properties at pH 6.8 showing 240- and 370-fold increase in weight. Compared to unmodified pullulan, Pul-TAEA and Pul-PEI displayed 5- and 13.3-fold increased dynamic viscosity in mucus. Mucoadhesion studies of Pul-TAEA and Pul-PEI on intestinal mucosa showed a 6- and 37.8-fold increase in tensile strength, and a 72- and 120-fold increase in mucoadhesion time compared to unmodified pullulan, respectively. Due to additional ionic interactions between cationic groups on polyaminated pullulans and an anionic model drug, a sustained drug release was achieved. CONCLUSIONS: Polyaminated pullulans are promising novel mucoadhesive excipients for mucosal drug delivery.

Charge-Converting Nanoemulsions as Promising Retinal Drug and Gene Delivery Systems.

AIM: This study aimed to develop phosphatase-responsive ζ potential converting nanocarriers utilizing polyphosphate-coated cell-penetrating peptide (CPP)-decorated nanoemulsions (NEs) as a novel gene delivery system to retinal cells. METHODS: Poly-l-lysine (PLL) was first conjugated with oleylamine (OA) only at its carboxylic end to form the amphiphilic PLL-oleylamine (PLOA) conjugate. Afterward, NEs were loaded with PLOA prior to being coated with tripolyphosphate (TPP) to generate PLOA/TPP NEs. A plasmid containing a reporter gene for green fluorescent protein plasmid (pGFP) was complexed with cationic surfactants forming hydrophobic ion pairs that were loaded in the oily core of NEs. Phosphate removal, ζ potential conversion, and cytotoxicity of the system were evaluated. Cellular uptake and transfection efficiency were investigated in 661W photoreceptor-like cells via microscopic analysis, fluorescence spectroscopy, and flow cytometry. RESULTS: Dephosphorylation of PLOA/TPP NEs triggered by alkaline phosphatase (ALP) resulted in the exposure of positive amine groups on the surface of NE droplets and a notable conversion of the ζ potential from -22.4 to +8.5 mV. Cellular uptake of PLOA/TPP NEs performed on 661W photoreceptor-like cells showed a 3-fold increase compared to control NEs. Furthermore, PLOA/TPP NEs also showed low cytotoxicity and high transfection efficacy with ∼50% of cells transfected. CONCLUSIONS: Polyphosphate-coated CPP-decorated NEs triggered by ALP could be a promising nanosystem to efficiently deliver drugs and genetic materials to photoreceptor-like cells and other retinal cells for potential treatments of retinal diseases.

Size shifting of solid lipid nanoparticle system triggered by alkaline phosphatase for site specific mucosal drug delivery.

We aim to prepare a size-shifting nanocarrier for site-targeting mucosal drug delivery that can penetrate through mucus gel layer and remain close to the absorption membrane. As nanocarriers can be engineered to penetrate mucus but they can also back diffuse into outer mucus regions, a size shifting to micron range once they have reached the absorption membrane would prevent back-diffusion effect and extend drug release over a long period of time. For this purpose, we loaded solid lipid nanoparticles (SLN) with a phosphate ester surfactant and octadecylamine. Alkaline phosphatase (AP), a membrane bound enzyme was for the first time utilized as an in situ partner for triggering the size conversion at epithelial cell surface. Having the size of ~120 nm, SLN with hydrophilic and phosphate-decorated shells were shown to penetrate through mucus gel and form aggregates above cell layer surface. Aggregates of 5-8 µm were formed due to interparticle interactions induced by enzymatic phosphate removal after ~30 min in contact with isolated AP. The developed SLN system could be a potential tool for mucosal drug delivery to AP-expressing tissues like colon, lung, cervix, vagina and some mucus-secreting tumors.

Polyphosphate coatings: A promising strategy to overcome the polycation dilemma.

AIM: It was the aim of this study to develop a zeta potential changing drug delivery system by decorating lipid-based nanocarriers with a polycationic cell penetrating peptide (CPP) and subsequently masking these cationic substructures with polyphosphates. METHODS: In order to anchor the CPP poly-l-lysine (PLL) on the surface of the oily droplets of an o/w nanoemulsion, stearic acid was covalently attached to the peptide. The resulting CPP-decorated oily droplets were coated with phytic acid and tripolyphosphate. The elimination of these polyphosphates due to cleavage by alkaline phosphatase was monitored by the release of monophosphate from the surface of the nanocarriers, by the change in zeta potential and by cellular uptake studies on Caco-2 cells. RESULTS: Polyphosphate coated PLL-decorated nanocarriers exhibited a pronounced conversion of zeta potential from -14.1 mV to +4.2 mV in case of tripolyphosphate coated nanocarriers and from -9.9 mV to -2.6 mV in case of phytic acid coated nanocarriers. The cellular uptake on Caco-2 cells of the polyphosphate coated nanocarriers was 4-fold improved compared to the control nanocarriers. Furthermore, confocal images showed that the majority of nanodroplets distributed in cytoplasm not being internalized into lysosomes. CONCLUSION: Polyphosphate coating of CPP-decorated nanocarriers seems to be a promising and simple strategy to overcome the polycation dilemma.

Solidification of self-emulsifying drug delivery systems (SEDDS): Impact on storage stability of a therapeutic protein.

Four solidification methods for self-emulsifying drug delivery systems (SEDDS) were compared to evaluate the impact of solidification on storage stability of an incorporated protein. Papain was loaded in SEDDS via hydrophobic ion pairing (HIP). Liquid SEDDS (l-SEDDS) were either solidified by adsorption to solid excipients such as magnesium-aluminometasilicate via wet granulation (ssilica-SEDDS) and carbohydrates via lyophilisation (scarbo-SEDDS) or by incorporation of high-melting PEG-surfactants (sPEG-SEDDS) and triglycerides (soil-SEDDS) in SEDDS preconcentrates. L- and s-SEDDS were compared regarding intrinsic emulsion properties, solid-state form of papain, enzyme stability and activity during storage. HIP with deoxycholate showed a precipitation efficiency of 82% and papain maintained 90% of its initial activity. Incorporated papain was present in an amorphous state, confirming a molecular dispersion in all preconcentrates. In comparison to l-SEDDS each solidification method investigated improved the storage stability of incorporated papain. Neither precipitation nor phase separation was observed for s-SEDDS. sPEG-SEDDS demonstrated with 87.8% the highest enzymatic activity and displayed according to the following rank order: sPEG-SEDDS > soil-SEDDS > ssilica-SEDDS > scarbo-SEDDS > l-SEDDS the highest remaining papain activity after 30 days of storage. This work clearly demonstrates that solidified SEDDS can provide a significantly improved storage stability for therapeutic proteins compared to corresponding liquid formulations.

The Effect of Counterions in Hydrophobic Ion Pairs on Oral Bioavailability of Exenatide.

The aim of this study was to evaluate the potential of n-octadecyl sulfate (SOS) as a counterion for hydrophobic ion pairing (HIP) with exenatide-a potent glucagon-like peptide-1 (GLP-1) analogue in the treatment of diabetes mellitus-to improve its oral bioavailability. Exenatide was ion-paired with SOS and docusate (DOC) serving as the gold standard followed by the incorporation in a self-emulsifying drug delivery system (SEDDS) comprising Capmul MCM EP, Captex 355, Kolliphor RH40, and propylene glycol at a mass ratio of 41:15:40:4. The hydrophobicity of exenatide-SOS and exenatide-DOC was characterized by determining the butanol-water partition coefficient (log Pbutanol/water). Droplet size and zeta potential of the ion pair-loaded SEDDS were characterized followed by intestinal membrane permeability determination on freshly excised rat intestines compared to exenatide solution. Furthermore, the oral bioavailability of exenatide-SOS- and exenatide-DOC-loaded SEDDS was also evaluated in vivo in healthy male Sprague-Dawley rats. Hydrophobic ion pairing increased the log Pbutanol/water of exenatide from -1.9 to 2.0 for exenatide-SOS and to 1.2 for exenatide-DOC. SEDDSs loaded with 0.26% (m/m) exenatide-SOS and 0.17% (m/m) exenatide-DOC had mean droplet size less than 30 nm and negative zeta potential. Ex vivo permeation experiments revealed 3.5-fold and 6.4-fold improvement in membrane permeability of the exenatide-SOS-loaded SEDDS vs. the exenatide-DOC-loaded SEDDS and exenatide solution, respectively. The orally administered exenatide-SOS-loaded SEDDS and exenatide-DOC-loaded SEDDS resulted in relative oral bioavailability vs. subcutaneous injection (SC) of 19.6 and 15.2%, respectively. Within this study, the key role of counterions for oral peptide delivery via HIP could be confirmed, and SOS was identified as a promising surfactant for this purpose.

Oral self-emulsifying delivery systems for systemic administration of therapeutic proteins: science fiction?

Objective: The aim of this study was to develop self-emulsifying drug delivery systems (SEDDS) for oral delivery of therapeutic proteins through hydrophobic ion pairing. Method: Horseradish peroxidase (HRP), a model protein, was ion paired with sodium docusate to increase its hydrophobicity. The formed enzyme - surfactant complex was incorporated into SEDDS, followed by permeation studies across Caco-2 cell monolayer and freshly excised rat intestine. Results: Hydrophobic ion pairs (HIP) were formed between HRP and sodium docusate with the efficiency of 87.49 ± 1.35%. The formed complex maintained 60.97 ± 1.48% of the original enzyme activity. The ion pair was subsequently loaded into SEDDS with a payload of 0.1% (mass per cent, m/m). The obtained emulsion formed by SEDDS had a droplet size in the range from 20 to 200 nm with negative zeta potential. Permeation mechanism of the enzyme was energy-dependent and the encapsulation of the HIP complex in SEDDS enhanced the permeation of the enzyme through the Caco-2 cell monolayer and freshly excised rat intestine by 4 times and 2.5 times compared to the free enzyme, respectively. Conclusion: According to these findings, hydrophobic ion pairing followed by incorporation to SEDDS might be considered as a potential strategy for oral delivery of therapeutic proteins.

Self-emulsifying drug delivery systems and cationic surfactants: do they potentiate each other in cytotoxicity?

OBJECTIVES: The aim of this study was to evaluate the cytotoxicity of self-emulsifying drug delivery systems (SEDDS) containing five different cationic surfactants. METHODS: Cationic surfactants were added in a concentration of 1% and 5% (m/m) to SEDDS comprising 30% Capmul MCM, 30% Captex 355, 30% Cremophor EL and 10% propylene glycol. The resulting formulations were characterized in terms of size, zeta potential, in-vitro haemolytic activity and toxicity on Caco-2 via MTT assay and lactate dehydrogenase release assay. KEY FINDINGS: The evaluated surfactants had in both concentrations a minor impact on the size of SEDDS ranging from 30.2 ± 0.6 to 55.4 ± 1.1 nm, whereas zeta potential changed significantly from -9.0 ± 0.3 to +28.8 ± 1.6 mV. The overall cytotoxicity of cationic surfactants followed the rank order: hexadecylpyridinium chloride > benzalkonium chloride > alkyltrimethylammonium bromide > octylamine > 1-decyl-3-methylimidazolium. The haemolytic activity of the combination of cationic surfactants and SEDDS on human red blood cells was synergistic. Furthermore, cationic SEDDS exhibited higher cytotoxicity of Caco-2 cells compared to SEDDS without cationic surfactants. CONCLUSIONS: According to these results, SEDDS and cationic surfactants seem to bear an additive up to synergistic toxic risk.

Chitosan based micelle with zeta potential changing property for effective mucosal drug delivery.

Mucus permeation, mucoadhesion and cell membrane interaction are properties that a drug carrier needs to deliver macromolecule compounds through the mucus barrier and inside epithelial cells effectively. Herein, we prepared micelles from phosphorylated chitosan-stearic acid conjugates (CSSAP) possessing those properties. Their zeta potential can be shifted from negative to neutral once contacting with alkaline phosphatase (ALP). CSSAP micelles showed effective mucus permeation and cell association, thus could be used as a promising platform for mucosal drug delivery. CSSAP was obtained via two modifications: alkylation of CS with stearic acid (termed CSSA) followed by phosphorylation utilizing phosphorus pentoxide. CSSAP had critical micelle concentration value of 76 µg/mL and phosphate content of 1066 µmol/g polymer. Micelle hydrodynamic size was 50-60 nm. Upon contacting with ALP, the polymeric micelles showed a phosphate release of 626 µmol/g polymer (~60%) and a zeta potential shift from -20 to -9 mV within 30 min. They exhibited 6-times higher mucus permeation capacity than positively charged CSSA micelles. CSSAP micelles association to Caco-2 and HEK 293 cells depended on the ALP activity. On Caco-2 cells, cell association rate after 3 h was 2-times higher compared to association rate in the presence of 0.5% phosphatase inhibitors.

Surface phosphorylation of nanoparticles by hexokinase: A powerful tool for cellular uptake improvement.

The aim of the study was to develop zeta potential changing nanoparticles (NPs) via surface phosphorylation in order to improve their uptake by epithelial cells. Polymeric NPs were formed via in situ gelation between chitosan (CS) and chondroitin sulphate (ChS). Phosphorylation of these NPs was carried out by using hexokinase. The resulting phosphorylated NPs (p-NPs) were characterized in respect of their size and zeta potential. Phosphate release was quantified by incubating the particles with isolated as well as cell-associated intestinal alkaline phosphatase (AP). In parallel, resulting change in zeta potential was monitored. In-vitro mucus permeation of these particles was evaluated on porcine intestinal mucus. Furthermore, toxicity and cellular uptake studies were performed on Caco-2 cells. p-NPs exhibited a mean size of 412 ±â€¯3.24 nm and a zeta potential of -12.4 mV. When these p-NPs were incubated with isolated as well as cell-associated AP, a significant amount of phosphate was released within 4 h and zeta potential raised up to -1.2 mV. p-NPs showed improved mucus permeation in comparison to unmodified NPs. Due to de-phosphorylation by AP, cellular uptake of p-NPs increased almost 2-fold. Moreover, particles displayed no toxicity. Findings of this study show that zeta potential changing p-NPs provide effective mucus permeation and enhanced cellular uptake.

Self-emulsifying drug delivery systems changing their zeta potential via a flip-flop mechanism.

To overcome the mucus layer and cell membrane barrier, self-emulsifying drug delivery systems (SEDDS) exhibiting negative zeta potential, switching to positive values when having reached the cell membrane is a promising approach. Accordingly, a novel conjugate was synthesized by covalent attachment of phosphotyrosine to octadecylamine, which was incorporated into SEDDS. Generated system presented an average diameter of 32 nm and zeta potential of around -12 mV when being diluted 1:100 in 100 mM HEPES buffer pH 7.5 containing 5 mM MgCl2 and 0.2 mM ZnCl2. Incubation of SEDDS with isolated intestinal alkaline phosphatase (IAP) resulting in enzymatic cleavage of phosphate ester moiety caused a shift in zeta potential up to +5.3 mV. As non-toxicity of the developed SEDDS diluted 1:1000 in 25 mM HEPES buffer pH 7.5 containing 5% glucose was observed on Caco-2 cells by employing resazurin assay, this system may provide an inspiring strategy for future zeta potential changing drug delivery systems to master the mucus and membrane barrier.