RESEARCH ARTICLE – Pharmaceutics, Drug Delivery and Pharmaceutical Technology

Bioactive Self-Assembling Lipid-Like Peptides as Permeation Enhancers for Oral Drug Delivery CHRISTINA KARAVASILI,1 MARIOS SPANAKIS,2 DIONYSIA PAPAGIANNOPOULOU,3 IOANNIS S. VIZIRIANAKIS,2 DIMITRIOS G. FATOUROS,1 SOTIRIOS KOUTSOPOULOS4 1

School of Pharmacy, Aristotle University of Thessaloniki, Department of Pharmaceutical Technology, Thessaloniki GR-54124, Greece School of Pharmacy, Aristotle University of Thessaloniki, Department of Pharmacology and Molecular Biology, Thessaloniki GR-54124, Greece 3 School of Pharmacy, Aristotle University of Thessaloniki, Department of Pharmaceutical Chemistry, Thessaloniki GR-54124, Greece 4 Center for Biomedical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 2

Received 14 November 2014; revised 12 April 2015; accepted 16 April 2015 Published online 20 May 2015 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/jps.24484 ABSTRACT: 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 C 2015 Wiley Periodicals, Inc. and the American Pharmacists Association facilitate oral delivery of diagnostic and therapeutic molecules.  J Pharm Sci 104:2304–2311, 2015 Keywords: lipid-like peptides; surfactant; designed tunable peptides; oral absorption; epithelial delivery; Caco-2 cells; absorption enhancer; formulation; intestinal absorption; macromolecular drug delivery; everted sacs

INTRODUCTION The oral bioavailability of many drugs including hydrophilic small molecules and biomacromolecules such as proteins and peptides is inhibited by poor absorption by the intestinal epithelial barrier. To facilitate the uptake of orally administered therapeutic molecules, permeation enhancers are coadministered. Such permeation enhancers may be low molecular mass chemical compounds (e.g., bile salts, fatty acids, lysolecithins)1,2 that enter the blood circulation and may cause systemic toxic side effects,2 or macromolecules (e.g., peptides such as zonula occluden toxin and melittin, polyacrylates, and chitosan derivatives)3–5 which do not enter the circulation but remain at the site where drug absorption takes place for prolonged periods of time, thus allowing for intestinal permeation of unwanted compounds.2 Furthermore, some permeation enhancers disrupt the epithelial cell membrane which may lead to the undesirable influx of solutes, undigested food components, Correspondence to: S. Koutsopoulos (Telephone: +617-752-2042; Fax: +617258-5239, E-mail: [email protected]) Marios Spanakis’ present address is Computational BioMedicine Laboratory Institute of Computer Science Foundation for Research and Technology-Hellas (Forth), P.O. Box 1385, Heraklion GR-70013, Crete, Greece. This article contains supplementary material available from the authors upon request or via the Internet at http://wileylibrary.com. Journal of Pharmaceutical Sciences, Vol. 104, 2304–2311 (2015)  C 2015 Wiley Periodicals, Inc. and the American Pharmacists Association

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metabolites of intestinal microorganisms, and bile salts.2 These shortcomings have necessitated the discovery of novel biocompatible, non-toxic agents that are highly efficient and specific for the transport of therapeutic compounds through the epithelial barrier of the intestine. Despite intense research conducted on natural and synthetic materials, these challenges have not been resolved yet. Molecular design and synthesis of biologically inspired biomolecules including lipids, peptides, oligonucleotides, and polysaccharides have significantly advanced the field of biomedicine.6,7 Depending on the amino acid sequence, synthetic, self-assembling peptides form hydrogels or nanovesicles with applications in biomedicine as permissive biological scaffolds for regenerative medicine and drug delivery.8–13 A class of self-assembling peptides was designed to mimic the lipids of biological membranes.14,15 When dissolved in electrolyte solutions such as biological fluids, lipid-like peptides self-assemble and form stable nanovesicles or micelles similar to lipids and other chemical surfactants.14–16 Previously, we showed that the ac-A6 K-CONH2 , KA6 -CONH2 , ac-A6 D-COOH, and DA6 -COOH lipid-like peptides formed nanovesicles, which are similar to liposomes, and we showed that they may be used for the formulation and controlled delivery of hydrophilic and hydrophobic compounds.13 Short, lipid-like peptides are non-toxic, non-immunogenic, and they are amenable to molecular design enabling

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RESEARCH ARTICLE – Pharmaceutics, Drug Delivery and Pharmaceutical Technology

modifications in the number, type, and order of amino acids on the peptide chain.17 The ease and low cost of large-scale production and the wide scope of modification allow for the synthesis of tailor-made sequences with tunable properties. The discovery of amphiphilic, lipid-like peptides has opened new avenues for applications in biotechnology for the stabilization of membrane proteins more efficiently than commercial detergents18–20 and in nanotechnology for the construction of energy conversion devices.21 In this work, we set out to investigate the biological properties of lipid-like peptides to enhance the permeability of the intestinal epithelium. As a model for our study, we used human colorectal adenocarcinoma Caco-2 cells. The effectiveness of Caco-2 cell monolayers in evaluating the transport enhancing properties of bioactive molecules has been widely demonstrated.22–24 To further confirm the in vitro results, we studied ex vivo the effect of ac-A6 D-COOH lipid-like peptides, which showed the highest permeability of fluorescein isothiocyanate (FITC)-dextran across cell monolayers, on the intestinal absorption of macromolecules using the everted gut sac method.25

MATERIALS AND METHODS Lipid-Like, Self-Assembling Peptides The amphiphilic peptides acetyl-AAAAAAK-CONH2 (acA6 K-CONH2 ), KAAAAAA-CONH2 (KA6 -CONH2 ), acetylAAAAAAD-COOH (ac-A6 D-COOH), and DAAAAAA-COOH (DA6 -COOH) were purchased from SynBioSci (Livermore, CA). Peptides were received in powder, dispersed in phosphate buffer saline (PBS; 100 mM KH2 PO4 , 10 mM Na2 HPO4 , 137 mM NaCl, 2.7 mM KCl at pH 7.4) and sonicated for 10 min using a bath sonicator to facilitate solubilization and dispersion and stored at room temperature. Mass Spectroscopy The peptides dissolved in deionized water were characterized by electrospray ionization-quadrupole-time-of-flight (ESIQ-TOF) mass spectrometry. Each peptide sample was loaded onto a Zorbax 300 Extend-C18 column (Agilent Technologies, Palo Alto, California) and an Agilent 1200 chromatography system coupled to Agilent 6510 Q-TOF (spray voltage of 3.8 kV, gas temperature of 275°C, nebulizer gas at 10 psi, and a drying gas of 4 L/min). Positive ion data-dependent acquisition range in the scan mode was 100–1799 m/z and for the MS/MS mode 100–2000 m/z. The charge priority of MS/MS acquisition was +2 (charges), +3, >+3, unknown, +1. Data were collected and analyzed using the Agilent MassHunter software (Agilent, Technologies). Peptide identification, assignment, and possible amino acid chemical modifications were performed by inspection of the MS/MS spectra and by using the ProteinProspector software (http://prospector.ucsf.edu/). Cell Viability Assay Caco-2 cells (passage 40) were cultured at 37°C in growth medium [i.e., Dulbecco’s modified Eagle medium (DMEM)], supplemented with 10% (v/v) fetal bovine serum, 1% (w/v) nonessential amino acids, and 100 :g/mL penicillin and streptomycin) in 5% (v/v) CO2 humidified atmosphere. The medium was changed every 2–3 days until cells reached 80% confluency in culture and then cells were trypsinized and subcultured. The effect of lipid-like peptides on cell viability and DOI 10.1002/jps.24484

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proliferation was studied using the MTT assay26 (i.e., 3-(4,5dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, Trevigen Inc., Gaithersburg, MD). Caco-2 cells grown to a density of 4 × 103 cells/cm2 in 96-well plates were incubated for 3, 24, and 48 h in growth medium containing 0.2 or 1.0 mg/mL of lipidlike peptides. Then, 10 :L of the MTT reagent were added and the plates were incubated for 3 h at 37°C. Absorbance of the R formazan product was determined at 600 nm with a Teknika ELISA plate reader after 1 h. Transepithelial Resistance and Cell Monolayer Permeability Caco-2 cells were seeded at a density of 2 × 105 cells/cm2 on 24-well Transwell inserts (0.4 :m pore size; Corning, Corning, NY) and the medium was changed every 2–3 days in both sides of the membrane. Formation of cell monolayer was confirmed microscopically. Then, the growth medium was replaced with 10 mM Hank’s balanced salt solution/[4-(2-hydroxyethyl)1-piperazineethanesulfonicacid] (HBSS/HEPES) buffer pH 7.4 with and without 0.2 or 1.0 mg/mL lipid-like peptides. To study the cell monolayer integrity and permeability, the transepithelial resistance (TEER) of the Caco-2 monolayers was monitored every 30 min for 5 h (Millicell-ERS; Millipore, Bedford, MA). At 180 min, the cell cultures were washed with DMEM to remove the lipid-like peptides, fresh HBSS/HEPES buffer was added, and TEER was measured for 120 min to assess the ability of cells to recover from treatment. For the permeability assay, we used Caco-2 monolayers with TEER values over 400 /cm2 (n = 4). In the apical side of the Transwells containing 0.2 or 1.0 mg/mL of lipid-like peptides in 10 mM HBSS/HEPES pH 7.4, we added 1 mg/mL FITC-dextran MW 4.4 kDa (FD4, 4.4 kDa; Sigma–Aldrich, St. Louis, MO). Samples were withdrawn periodically from the basolateral side and FITC-dextran was measured using a fluorescence plate reader (excitation and emission were 490 and 530 nm, respectively). Results were expressed as mean ± SD cumulative transepithelial transport of FITC-dextran time. The apparent permeability coefficient is Papp = versus   dQ dt (A Co ) in cm/s, where dQ is the cumulative amount of FITC-dextran in the basolateral side at time t, (dQ/dt) in pmol/s is the permeability rate, Co in pmol is the initial concentration of FITC-dextran in the apical side, and A in cm2 is the area The   permeation enhancement ratio  of the monolayer. is R = Papp (peptide) Papp (control) . Student’s t-test was performed to determine whether the differences observed in Papp were statistically significant (t-test, p 0.05). Notably, 48 h after treatment with 0.2 and 1.0 mg/mL ac-A6 D-COOH, we consistently observed a 29% and 20% increase, respectively, in cell numbers compared with the control (containing no peptide). Further work will be required to interpret the effect of ac-A6 D-COOH peptides on Caco-2 cell proliferation. TEER Across Caco-2 Monolayers in the Presence of Lipid-Like Peptides We then set out to explore the ability of lipid-like peptides to facilitate or amplify the bioavailability of therapeutic molecules.

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Successful management of disease requires delivery of therapeutic agents in effective concentrations. However, this may be challenging because of low permeability of epithelial (e.g., gastrointestinal tract, eye conjunctiva) and endothelial (e.g., blood brain barrier) layers to many pharmaceuticals. To increase the bioavailability of drugs, various permeation enhancers have been developed, some of which have surfactant properties. In this study, we measured the effect of lipid-like peptides on the transport of FITC-dextran across Transwell filter-grown Caco-2 cell monolayers that represent an in vitro model system to study epithelial permeability.22,23 Reduction of the resistance across the epithelial monolayer indicates that the integrity of the monolayer is compromised. Our results show that the presence of lipid-like peptides did not affect the TEER compared with the control (Figs. 3a and 3b). A small time-dependent decrease in TEER was observed in all samples including the control and is due to a small dilation of the tight junctions in 10 mM HBSS/HEPES buffer, resulting in increased permeability of the monolayer to small ions.33 At 180 min (arrow in Figs. 3a and 3b), cell cultures were washed with DMEM and fresh, peptidefree, HBSS/HEPES buffer was added. In all cases, the TEER returned to 95%–100% of the pretreatment values suggesting that the observed TEER decrease over time is reversible. These results suggest that lipid-like peptides do not compromise the Caco-2 monolayer integrity. Lipid-Like Peptides as Permeation Enhancers To assess the effect of lipid-like peptides on permeability through Caco-2 monolayers, we used FITC-dextran 4.4 kDa, which is a hydrophilic paracellular route transport marker. FITC-dextran transport across monolayers without coapplication of lipid-like peptides is small (Figs. 3c and 3d). Addition of 1.0 mg/mL of ac-A6 D-COOH, DA6 -COOH, ac-A6 KCONH2 , and KA6 -CONH2 lipid-like peptides resulted in 7.6, 6.2, 5.3, and 6.5-fold, respectively, increased FITC-dextran transport through the cell monolayers compared with the control (p < 0.05) (Figs. 3c and 3d; Table 2). Permeation enhancement ratios (R) in this range may result in increased drug transport through the epithelial barrier without compromising the integrity of the intestinal epithelial layer. High FITC-dextran transport values were also observed when 0.2 mg/mL of ac-A6 D-COOH, DA6 -COOH, ac-A6 K-CONH2 , and KA6 -CONH2 peptides were added in the Transwell monolayer cultures resulting in 6.6, 5.2, 5.2, and 5.0-fold, respectively, increased transport compared with the control. Although the

Table 2. Apparent Permeability Coefficient (Papp ) and Enhancement Ratio (R) of FITC-Dextran 4.4 kDa Transport Through Caco-2 Monolayers in the Presence of Lipid-Like Peptides Peptide Control ac-A6 K-CONH2 KA6 -CONH2 Figure 2. Effect of lipid-like peptides on Caco-2 cell viability after 3, 24, and 48 h in culture. Error bars represent the mean ± SD (n = 4). The differences in the number of viable cells at each condition compared with the control are not significant (p > 0.05). DOI 10.1002/jps.24484

ac-A6 D-COOH DA6 -COOH

Concentration (mg/mL)

Papp (10−6 cm/s)

Ratio R

– 0.2 1.0 0.2 1.0 0.2 1.0 0.2 1.0

0.82 ± 0.31 4.27 ± 1.38 4.35 ± 1.77 4.09 ± 1.44 5.36 ± 1.51 5.42 ± 1.59 6.20 ± 1.60 4.30 ± 2.15 5.09 ± 0.82

– 5.2 5.3 5.0 6.5 6.6 7.6 5.2 6.2

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Figure 3. Transepithelial resistance of Caco-2 cell intestinal epithelia in the presence of (a) 0.2 mg/mL and (b) 1.0 mg/mL lipid-like peptides. The arrow indicates the time point at which the peptides were removed from the growth medium and shows the monolayer recovery process. (c and d) Permeation of FITC-dextran from the apical to the basolateral side of Caco-2 cell monolayers at (c) 0.2 mg/mL and (d) 1.0 mg/mL of peptides. Data are shown as mean ± SD (n = 4, p < 0.05 compared with the control).

Caco-2 monolayer model does not include the mucus layer, which is present in some epithelial layers, such absorption enhancement ratios in vitro suggest that these lipid-like peptides may be effective and safe absorption enhancers for delivery of macromolecules. The concentration-independent permeation enhancement of FITC-dextran at low and high lipid-like peptide concentrations suggests saturation of the monolayers with peptide for which the transport capacity reached a ceiling value. Such behavior has been previously observed in the transport of PEG-4000 across Caco-2 cell monolayers,34 when increased concentrations of chitosan glutamate did not increase proportionally the transport of the hydrophilic marker. The transport of FITC-dextran across the epithelium monolayer in the presence of the lipid-like peptides followed the order ac-A6 D-COOH > DA6 -COOH > ac-A6 K-CONH2 > KA6 -CONH2 for the low concentration (0.2 mg/mL), whereas at high concentrations (1 mg/mL), its order was ac-A6 D-COOH > KA6 CONH2 > DA6 -COOH > ac-A6 K-CONH2 . These data might be explained in light of the morphology and the composition of the lipid-like peptides. Previously developed N-acetylated "amino acids and N-acetylated non-"-amino acids considerably enhanced the absorption of calcitonin,35 cromolyn,36 and recombinant human growth hormone in vivo.37 Therefore, we may hypothesize that the higher permeation rates observed in the case of ac-A6 D-COOH might be attributed to N-acetylation of the peptide. In a previous study,13 atomic force microscopy and light scattering analyses of the positively charged lipid-like ac-A6 KCONH2 , KA6 -CONH2 peptide formulations showed individual nanovesicles of approximately 126 and 169 nm, respectively, whereas negatively charged ac-A6 D-COOH and DA6 -COOH peptides self-assembled into nanovesicles that formed clusters with individual nanovesicles of 28 and 44 nm, respectively. Therefore, we cannot exclude the possibility that the large posKaravasili et al., JOURNAL OF PHARMACEUTICAL SCIENCES 104:2304–2311, 2015

itively charged lipid-like peptide nanovesicles accumulate onto the monolayers impeding the permeation of the paracellular marker FITC-dextran, whereas the smaller negatively charged lipid-like nanovesicles do not block the transport of the hydrophilic molecule. Immunocytochemical Studies in the Presence of Lipid-Like Peptides To investigate the effect of lipid-like peptides on cell morphology and tight junctions, we performed immunostaining against E-cadherin, a transmembrane glycoprotein and major component of the adherens junctions, which regulates the formation of tight junctions and Caco-2 monolayer polarity. E-cadherin is used as cell-to-cell junction marker of epithelial adhesion because of its function in the formation of tight junctions.29,38,39 Downregulation of E-cadherin or redistribution of the tight junction complexes away from the apicolateral membrane is correlated with disruption of the cell monolayer integrity allowing free diffusion of small molecules and proteins. Our results show that 0.2 or 1.0 mg/mL lipid-like peptides do not affect the Caco-2 cell morphology and monolayer integrity (Fig. 4). Ecadherin staining is strongly positive in peptide-treated Caco-2 monolayers adding further support to the TEER results, which did not show decreased electrical resistance across the monolayer in the presence of the lipid-like peptides. This suggests that the increased FITC-dextran transport across the Caco-2 monolayers in the presence of lipid-like peptides is not because of cell monolayer compromise and may have involved a transcellular transport mechanism.40 Together, our results show that lipid-like peptides do not affect Caco-2 cell viability and proliferation. Furthermore, they enhance the transport of the probe molecule FITCdextran across Caco-2 monolayers without compromising their integrity. DOI 10.1002/jps.24484

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Figure 4. Caco-2 cell monolayers treated with 0.2 or 1.0 mg/mL lipid-like peptides for 24 h. E-cadherin stains the adherens junctions of the epithelial cell membrane (red). Cell nuclei were stained with DAPI (blue). Scale bar is 50 :m.

Effect of Lipid-Like Peptides on the Intestinal Absorption of Macromolecules The absorption of FITC-dextran 4.4 kDa and 99m Tc-BSA through the intestinal wall was investigated in the presence and the absence of 1.0 mg/mL ac-A6 D-COOH lipid-like peptide using the everted gut sac method. The results of the in vitro studies showed that the presence of ac-A6 D-COOH lipid-like peptides increased the FITC-dextran transport across Caco-2 monolayers more than the transport values observed for FITCdextran in the presence of the other peptides (Table 2). Therefore, for the ex vivo experiments, we set out to study the effect of ac-A6 D-COOH on the intestinal absorption of FITC-dextran (4.4 kDa) and 99m Tc-BSA (66 kDa). Consistent with the Caco-2 monolayer transport studies, the luminal-to-serosal clearance of FITC-dextran and 99m Tc-BSA across jejunum sacs was increased upon addition of 1.0 mg/mL ac-A6 D-COOH. Figures 5 and 6 show our results on the transport of FITC-dextran and 99m Tc-BSA from the mucosal to the serosal side in 30 and 120 min. In the case of FITC-dextran intestinal absorption, at 30 min, there was no significant dif-

Figure 5. Relative permeability (nmol/cm2 ) of FITC-dextran 4.4 kDa at 30 and 120 min with and without 1.0 mg/mL ac-A6 D-COOH lipidlike peptide using the everted sacs method. In each box chart, the bottom (×) shows the minimum value, and marks the 0th percentile. The bottom of the box marks the 25th percentile and the top of the box marks the 75th percentile. The square symbol () in the box marks the mean. The top (×) shows the maximum value and 100th percentile. n = 4 sample points. DOI 10.1002/jps.24484

ference in the transport of FITC-dextran with and without 1.0 mg/mL ac-A6 D-COOH lipid-like peptide (t-test, p > 0.05). However, a significantly increased transport (50% higher compared with the control, t-test, p < 0.05) of the dye across the

Figure 6. Effect of the lipid-like peptide ac-A6 D-COOH on the intestinal absorption of 99 Tc-BSA. (a) Serosal transfer and (b) tissue uptake of 99 Tc-BSA at 30 and 120 min with and without 1.0 mg/mL ac-A6 DCOOH, using the everted sacs method. In each box chart, the bottom (×) shows the minimum value, and marks the 0th percentile. The bottom of the box marks the 25th percentile and the top of the box marks the 75th percentile. The square symbol () in the box marks the mean. The top (×) shows the maximum value and 100th percentile. n = 4 sample points. Karavasili et al., JOURNAL OF PHARMACEUTICAL SCIENCES 104:2304–2311, 2015

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tissue was observed at 120 min (Fig. 5). These results suggest that ac-A6 D-COOH facilitated the absorption of FITC-dextran 4.4 kDa by increasing the permeability of the dye across the intestinal walls over time. The transport of 99m Tc-BSA from the mucosal to the serosal side of the intestine and the uptake of 99m Tc-BSA by the intestinal tissue upon addition of 1.0 mg/mL ac-A6 D-COOH lipid-like peptide is shown in Figure 6. The results show that addition of the lipid-like peptide resulted in 1.3-fold increased absorption of 99m Tc-BSA to the serosal fluid compared with the control (Fig. 6a). The results obtained with the everted sac model demonstrate a dependence of permeation enhancement rate upon the molecular weight of the permeant with the higher transport rates observed for the lower molecular weight permeant (FITC-dextran 4.4 kDa) compared with their congener BSA (66 kDa). Furthermore, the amount of 99m Tc-BSA uptake by the tissue was increased in the presence of ac-A6 D-COOH (Fig. 6b); however, this increase was not significantly different compared with the control (t-test, p > 0.05). Moreover, after 120 min, no significant difference of 99m Tc-BSA uptake (t-test, p > 0.05) was observed between the control and the peptide-treated tissue. The tissue uptake of BSA in the presence of ac-A6 D-COOH was higher compared with that transported to serosal, indicating tissue accumulation. In the presence of ac-A6 D-COOH, the fraction of FITCdextran and BSA transported at 120 min was calculated to be 3.46 ± 0.93% and 2.61 ± 0.21%, respectively, whereas in the absence of the peptide, the respective values were calculated to be 2.33 ± 0.36% and 1.99 ± 0.35%.

CONCLUSIONS In this study, amphiphilic lipid-like peptides were tested as permeation enhancers. Our findings suggest that the amino acid sequence and the type of charge of the lipid-like peptides are important parameters to modulate the transport of FITC-dextran across the epithelial monolayer. Furthermore, we showed that transfer of the macromolecule FITC-dextran through the intestinal wall of everted sacs is increased in the presence of the negatively charged ac-A6 D-COOH lipid-like peptide and, therefore, it may be preferable as permeation enhancer for oral drug administration. In the case of BSA, a small effect on the transport was noticed in the presence of ac-A6 D-COOH. Given that other chemical compounds including fatty acids have been previously tested in vivo at similar concentrations as absorption enhancers, we believe that these synthetic, inexpensive, and versatile peptides represent an alternative to traditional systems to improve the oral delivery of small molecules and biotechnology-derived drugs (e.g., insulin, calcitonin) using various oral formulation platforms (e.g., tablets, enteric-coated solid dosage forms, capsules).

ACKOWLEDGMENTS C.K. is supported by the Onassis Foundation with a PhD scholarship. The Center for Environmental Health Sciences (CEHS; grant no. NIEHS ES002109) at MIT is acknowledged for mass spectrometric analysis and technical support. Karavasili et al., JOURNAL OF PHARMACEUTICAL SCIENCES 104:2304–2311, 2015

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DOI 10.1002/jps.24484

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Karavasili et al., JOURNAL OF PHARMACEUTICAL SCIENCES 104:2304–2311, 2015

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 desig...
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