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

Gemini surfactant-like peptide-based nanocages with β-sheet-enhanced stability and encapsulation efficiency of hydrophobic anticancer drugs

Peptide-based scaffolds have been widely applied to drug delivery because of their ease and high yields of synthesis, well-defined structure, biocompatibility, diversity, tunability of properties, and molecular recognition abilities. However, the stability of peptide-based nanostructures highly depends on the intermolecular assembling manner, e.g., α-helix based coiled coils, β-sheet. Inspired by the robust protein fibril structures in amyloidosis, herein we constructed a β-sheet-forming gemini surfactant-like peptide to self-assemble into nanocages with the help of molecular dynamics simulation. As expected, the experimental results showed that nanocages can be formed with the inner diameter of up to ∼400 nm, which were robust enough even under both transmission electron microscopy and atomic force microscopy, indicating the significant contribution of β-sheet conformation. The β-nanocages can load hydrophobic anticancer drugs, e.g., paclitaxel with a very high encapsulation efficiency, which holds great potential for clinic drug delivery due to the improved anticancer effect as compared with paclitaxel alone.

Fabrication of 3D-printed octreotide acetate-loaded oral solid dosage forms by means of semi-solid extrusion printing

Semi-solid extrusion (SSE) 3D printing technology was utilized for the encapsulation of octreotide acetate (OCT) into 3D-printed oral dosage forms in ambient conditions. The inks and the OCT-loaded 3D-printed oral dosage forms were characterized by means of rheology, Fourier-transform infrared (FTIR) spectroscopy and Nuclear Magnetic Resonance (NMR). In vitro studies demonstrated that the formulations released OCT in a controlled manner. The application of these formulations to Caco-2 cell monolayers revealed their capability to induce the transient opening of tight junctions in a reversible manner as evidenced by Transepithelial Resistance (TEER) measurements. Cellular assays (CCK-8 assay) demonstrated the viability of intestinal cells in the presence of these formulations. The in vitro transport studies across Caco-2 monolayers demonstrated the ability of these formulations to enhance the OCT uptake across the cell monolayer over time due to opening of the tight junctions.

Development and validation of HPLC-DAD and LC-(ESI)/MS methods for the determination of sulfasalazine, mesalazine and hydrocortisone 21-acetate in tablets and rectal suppositories: In vitro and ex vivo permeability studies

Controlled-release tablets and rectal suppositories of sulfasalazine (SLF) and hydrocortisone 21-acetate (HA) were prepared as recommended dosage forms for the treatment of acute episodes of ulcerative colitis, in patients who do not respond to monotherapy. A High-Performance Liquid Chromatography (HPLC) Diode-array method with a gradient elution mobile phase was developed to evaluate the production quality of both formulations (assay and dissolution profiles in gastric and intestinal fluids). Method's validation was carried out providing good linearity (r ≥ 0.9995), precision (RSD < 1.53%), recovery (96.9% - 103.7%) and limits of detection (LOD_SLF = 12 ng/mL, LOD_HA = 15 ng/mL). Experimental design and Plackett-Burman methodology was constructed to study the robustness of the analysis. In all composite substrates, a freezing lipid precipitation approach was used as purification step. The method was optimized by applying Central Composite design mode. The in-vitro/ex-vivo permeability studies of both formulations were evaluated by a Liquid Chromatography-Electron Spray Ionization Mass Spectrometry (LC-ESI/MS) +/- mode. The analysis of sulfamethazine (internal standard, SLM, m/z 279), HA (m/z 449, [M + HCOO]^-), SLF (m/z 399) and its active metabolite mesalazine (MSL, m/z 154) was performed using a C₁₈ column and gradient elution. The validation of the method met the requirements of the International Council for Harmonization (ICH) (r ≥ 0.9997, RSD ≤ 4.62%, Recovery > 95%, LOD_SLF = 1.28 ng/mL, LOD_HA = 1.07 ng/mL, LOD_MSL = 3.16 ng/mL). Based on the results, important conclusions were drawn concerning the role of excipients and SLF metabolism.

Facile design of gemini surfactant-like peptide for hydrophobic drug delivery and antimicrobial activity

Recently, many kinds of gemini-type amphiphilic peptides have been designed and shown their advantage as self-assembling nanomaterials. In this study, we proposed a simple strategy to design gemini surfactant-like peptides, which are only composed of natural amino acids and can be easily obtained by conventional peptide sythnesis. Taking two prolines as the turn-forming units, a peptide named APK was designed. The petide has a linear sequence but naturally takes the conformation like a gemini surfactant. Compared with a single-tailed surfactant-like peptide A6K, APK showed much stronger ability to undergo self-assembly and to encapsulate hydrophobic pyrene. Several hydrophobic drugs including paclitaxel, doxorubicin, etomidate and propofol were encapsulated by APK, and the corresponding formulations showed anti-tumor or anesthetic efficacy comparable to their respective clinical formulations. Furthermore, APK could inhibit the growth of different microorganisms including E. coli, S. aureus and C. albicans. Etomidate and propofol formulations encapsulated by APK also showed strong antimicrobial activity. Taking APK as an example, our study indicated a straightforward strategy to design gemini surfactant-like peptides, which could be potential nanomaterials for exploring hydrophobic drug formulations with efficacy, safety and self-antimicrobial activity.

Self-assembling peptides cross-linked with genipin: resilient hydrogels and self-standing electrospun scaffolds for tissue engineering applications

Self-assembling peptides (SAPs) are synthetic bioinspired biomaterials that can be feasibly multi-functionalized for applications in surgery, drug delivery, optics and tissue engineering (TE). Despite their promising biocompatibility and biomimetic properties, they have never been considered real competitors of polymers and/or cross-linked extracellular matrix (ECM) natural proteins. Indeed, synthetic SAP-made hydrogels usually feature modest mechanical properties, limiting their potential applications, due to the transient non-covalent interactions involved in the self-assembling phenomenon. Cross-linked SAP-hydrogels have been recently introduced to bridge this gap, but several questions remain open. New strategies leading to stiffer gels of SAPs may allow for a full exploitation of the SAP technology in TE and beyond. We have developed and characterized a genipin cross-linking strategy significantly increasing the stiffness and resiliency of FAQ(LDLK)3, a functionalized SAP already used for nervous cell cultures. We characterized different protocols of cross-linking, analyzing their dose and time-dependent efficiency, influencing stiffness, bioabsorption time and molecular arrangements. We choose the best developed protocol to electrospin into nanofibers, for the first time, self-standing, water-stable and flexible fibrous mats and micro-channels entirely made of SAPs. This work may open the door to the development and tailoring of bioprostheses entirely made of SAPs for different TE applications.

Strategies for the enhanced intracellular delivery of nanomaterials

The intracellular delivery of nanomaterials and drugs has been attracting increasing research interest, mainly because of their important effects and functions in several organelles. Targeting specific organelles can help treat or decrease the symptoms of diabetes, cancer, infectious, and autoimmune diseases. Tuning biological and chemical properties enables the creation of functionalized nanomaterials with enhanced intracellular uptake, ability to escape premature lysosome degradation, and to reach a specific target. Here, we provide an update of recent advances in the intracellular delivery mechanisms that could help drugs reach their target more efficiently.

Peptide self-assembly into lamellar phases and the formation of lipid-peptide nanostructures

Lipids exhibit an extraordinary polymorphism in self-assembled mesophases, with lamellar phases as biologically most relevant representative. To mimic lipid lamellar phases with amphiphilic designer peptides, seven systematically varied short peptides were engineered. Indeed, four peptide candidates (V₄D, V₄WD, V₄WD₂, I₄WD₂) readily self-assembled into lamellae in aqueous solution: small-angle X-ray scattering patterns (SAXS) revealed ordered lamellar structures with a repeat distance of ~4-5 nm. Transmission electron microscopy (TEM) images confirmed the presence of stacked sheets. Two derivatives (V₃D and V₄D₂) remained as loose aggregates dispersed in solution; one peptide (L₄WD₂) formed twisted tapes with internal lamellae and an antiparallel β-type monomer alignment. To understand the interaction of peptides with lipids they were mixed with phosphatidylcholines. Low peptide concentrations (1.1 mM) induced the formation of a heterogeneous mixture of vesicular structures: large multilamellar vesicles (d-spacing ~6.3 nm) coexisted with oligo- or unilamellar vesicles (~50 nm in diameter) and bicelle-like structures (~45 nm length, ~18 nm width). High peptide concentrations (11 mM) led to unilamellar vesicles (ULV, diameter ~260-280 nm) with a homogeneous mixing of lipids and peptides. SAXS revealed the temperature-dependent fine structure of these ULVs: at 25 °C the bilayer is in a fully interdigitated state (headgroup-to-headgroup distance dhh ~2.9 nm), whereas at 50 °C this interdigitation opens up (dhh ~3.6 nm). Our results highlight the versatility of self-assembled peptide superstructures: subtle changes in the amino acid composition are key design elements in creating peptide- or lipid-peptide nanostructures with the same richness in morphology as known from the lipid-world.

Mucus models to evaluate the diffusion of drugs and particles

Mucus is a complex hydrogel that acts as a natural barrier to drug delivery at different mucosal surfaces including the respiratory, gastrointestinal, and vaginal tracts. To elucidate the role mucus plays in drug delivery, different in vitro, in vivo, and ex vivo mucus models and techniques have been utilized. Drug and drug carrier diffusion can be studied using various techniques in either isolated mucus gels or mucus present on cell cultures and tissues. The species, age, and potential disease state of the animal from which mucus is derived can all impact mucus composition and structure, and therefore impact drug and drug carrier diffusion. This review provides an overview of the techniques used to characterize drug and drug carrier diffusion, and discusses the advantages and disadvantages of the different models available to highlight the information they can afford.

Self-Assembling RADA16-I Peptide Hydrogel Scaffold Loaded with Tamoxifen for Breast Reconstruction

More and more breast cancer patients prefer autologous fat tissue transfer following lumpectomy to maintain perfect female characteristics. However, the outcome was not satisfactory due to the transplanted fat absorption. In this study, we prepared two RADA16-I peptide scaffolds with and without tamoxifen. Both scaffolds were transparent, porous, and hemisphere-shaped. The hADSCs isolated from liposuction were attached to the scaffold. The growth inhibition of the hADSCs induced by TAM in 2-demensional (2D) culture was higher than that in TAM-loaded hydrogel scaffold 3D culture (P < 0.05); however, the same outcomes were not observed in MCF-7 cells. Correspondingly, the apoptosis of the hADSCs induced by TAM was significantly increased in 2D culture compared to that in scaffold 3D culture (P < 0.05). Yet the outcomes of the aoptosis in MCF-7 were contrary. Apoptosis-related protein Bcl-2 was involved in the process. In vivo experiments showed that both scaffolds formed a round mass after subcutaneous implantation and it retained its shape after being pressed slightly. The implantation had no effect on the weight and activity of the animals. The results suggested that TAM-loaded RADA16-I hydrogel scaffolds both provide support for hADSCs cells attachment/proliferation and retain cytotoxic effect on MCF-7 cells, which might be a promising therapeutic breast tissue following lumpectomy.

Self-assembling peptide-based building blocks in medical applications

Peptides and peptide-conjugates, comprising natural and synthetic building blocks, are an increasingly popular class of biomaterials. Self-assembled nanostructures based on peptides and peptide-conjugates offer advantages such as precise selectivity and multifunctionality that can address challenges and limitations in the clinic. In this review article, we discuss recent developments in the design and self-assembly of various nanomaterials based on peptides and peptide-conjugates for medical applications, and categorize them into two themes based on the driving forces of molecular self-assembly. First, we present the self-assembled nanostructures driven by the supramolecular interactions between the peptides, with or without the presence of conjugates. The studies where nanoassembly is driven by the interactions between the conjugates of peptide-conjugates are then presented. Particular emphasis is given to in vivo studies focusing on therapeutics, diagnostics, immune modulation and regenerative medicine. Finally, challenges and future perspectives are presented.