Nanocarrier for Oral Peptide Delivery Produced by Polyelectrolyte Complexation in Nanoconfinement

Opposites Attract: Electrostatically Driven Loading of Antimicrobial Peptides into Phytoglycogen Nanocarriers

Antimicrobial peptides, such as GL13K, have a high binding selectivity toward bacterial membranes, while not affecting healthy mammalian cells at therapeutic concentrations. However, delivery of these peptides is challenging since they are susceptible to proteolytic hydrolysis and exhibit poor cellular uptake. A protective nanocarrier is thus proposed to overcome these obstacles. We investigate the potential to employ biodegradable phytoglycogen nanoparticles as carriers for GL13K using a simple loading protocol based on electrostatic association rather than chemical conjugation, eliminating the need for control of chemical cleavage for release of the peptide in situ. Both the native (quasi-neutral) and carboxymethylated (anionic) phytoglycogen were evaluated for their colloidal stability, loading capacity, and release characteristics. We show that the anionic nanophytoglycogen carries a greater cationic GL13K load and exhibits slower release kinetics than native nanophytoglycogen. Isotope exchange measurements demonstrate that the antimicrobial peptide is entrapped in the pores of the dendritic-like macromolecule, which should provide the necessary protection for delivery. Importantly, the nanoformulations are active against a Pseudomonas aeruginosa clinical isolate at concentrations comparable to those of the free peptide and representative, small molecule antibiotics. The colloidal nanocarrier preserves peptide stability and antimicrobial activity, even after long periods of storage (at least 8 months).

Shining a new light on the structure of polyurea/polyurethane materials

Polyurea and polyurethane are widely used in coatings, foams, and micro- and nanocapsules. Investigations of the polymers structure indicate that a significant amount of hydrolyzed isocyanate is incorporated in the macromolecular backbone.

Aqueous core and hollow silica nanocapsules for confined enzyme modules

The development of enzyme modules by coupling several enzymes in confinement is of paramount importance to artificial biological reaction systems for efficient enzymatic reactions. Silica nanocapsules are ideal candidates for loading enzymes. Aqueous core silica nanocapsules have relatively been rarely reported due to the crux of difficulty in forming dense silica shells by interfacial sol-gel reactions. Herein we suggest a one-step synthesis of hollow silica nanocapsules with an aqueous core containing enzymes via a template-free and interfacial condensation method for developing enzyme modules with coupled enzymatic reactions. As a proof-of-concept, we developed enzyme modules for three useful purposes by encapsulating a couple of enzymes: (i) development of a miniature glucose sensor, (ii) protection of living cells, and (iii) regeneration of nicotinamide adenine dinucleotides (NADs). By the modulation of enzymes using silica nanocapsules, more efficient coupled reactions, separation of enzymatic reactions from surroundings, and easy handling of several enzymes by using a single module could be achieved. Therefore, our silica nanocapsules for enzyme modules can be promoted as general platforms for developing artificial nanoreactors.

Core–shell particles for drug-delivery, bioimaging, sensing, and tissue engineering

Core–shell particles offer significant advantages in their use for bioimaging and biosensors.

Polyelectrolyte-Based Platforms for the Delivery of Peptides and Proteins

The use of peptides and proteins in the pharmaceutical field has increased dramatically over recent years. They have been especially relevant to advances in the treatment of cancer, rheumatoid arthritis, leukemia, and cardiovascular, ophthalmological, metabolic, and infectious diseases. Despite the great potential of peptides and proteins, their use in pharmaceuticals has failed to reach its full potential because of some outstanding challenges. They are unstable under storage conditions and in biological milieus, and their high molecular weight limits permeation through biological membranes. A variety of delivery systems have been investigated to overcome these limitations. Polyelectrolytes (PEs) are molecules that bear multiple negative or positive charges. These molecules play an important role in various platforms relating to the delivery of peptide/protein-based drugs and subunit vaccines. The most commonly utilized PEs include chitosan, alginate, chondroitin sulfate, and poly(γ-glutamic acid). PE-based delivery systems, such as polyelectrolyte complexes (PECs), PE-coated nanocarriers, and PE multilayers, were designed to protect peptides and proteins from degradation and facilitate their absorption. These delivery systems are especially effective when administered orally or intranasally. This review emphasizes the important role of PEs and PE-based delivery vehicles in peptide/protein-based drugs and vaccines.

pH and folic acid dual responsive polysaccharide nanospheres used for nuclear targeted cancer chemotherapy

Ideal nanoscale drug delivery system (DDS) should be biocompatible, having targeted recognition and controlled release properties. In this work, monodispersed, doxorubicin (Dox) loaded chitosan (Cts) nanospheres functionalized by mesoporous SiO₂ and folic acid (FA) were prepared, briefly named as DCSF NSs. The prepared raspberry-like DCSF NSs had an average size of 440 nm and drug loading efficiency (DLE) of 42.61%. The drug release results confirmed that the release of Dox could be controlled by pH change. Cell apoptosis results indicated that the obtained DCSF NSs could kill 90% of MCF-7 cells in 48 h. Confocal laser scanning microscopy (CLSM) results further revealed that folic acid could mediate the cellular uptake of DCSF NSs. These results demonstrated that the obtained DCSF NSs were pH-responsive, folic acid-triggered nuclear targeted, which can be used as ideal DDS for tumor chemotherapy.

Encapsulation and Release of Functional Nanodroplets Entrapped in Nanofibers

A method is presented for preserving the structural integrity of nanodroplets produced by emulsification. Droplets of different hydrophobic liquids such as essential oils or monomers are produced by the miniemulsion process. The miniemulsions are then electrospun to yield dextran nanofibers entrapping the hydrophobic nanodroplets. The nanodroplets are then successfully redispersed by dissolving the nanofibers in water. Furthermore, it is shown that nanofibers can be used to store a monomer and a catalyst as healing agents for ring-opening metathesis polymerization. After dissolution, the healing agents are released and a self-healing reaction takes place. Embedding, storage, and release of emulsion nanodroplets is a promising method that avoids potential destabilization of droplets by coalescence or Ostwald ripening.

Influence of different classes of crosslinkers on alginate polyelectrolyte nanoparticle formation, thermodynamics and characteristics

Complexation of linear alginate polyanions with different classes of crosslinkers (divalent cations, polycations, positively charged surfactants) was investigated, to unravel their effects on nanoparticle formation. The goal was to define the crosslinker-to-alginate molar ratios at which nanoparticles are formed, and to reveal the underlying thermodynamics and molecular interactions using dynamic and electrophoretic light scattering, isothermal titration calorimetry, and infrared spectroscopy. Alginate nanoparticles were formed across a limited range of molar ratios that was specific for each crosslinker, and had different size and stability. Thermodynamic parameters of alginate complexation with crosslinkers showed that nanoparticle formation was in all cases entropy driven, together with a minor enthalpic contribution. The crosslinking mechanism was based on ionic interactions, with accompanying weaker interactions specific for each crosslinker, and involved characteristic macroscopic association constants (K_a1) for complexation of alginate (range, 10⁴-10⁹M^-1). Additionally, the ionic strengths of the media influenced the characteristics and stabilities of the polyelectrolyte nanoparticles.

Sequence-Controlled Delivery of Peptides from Hierarchically Structured Nanomaterials

Peptide drugs delivered orally need to be protected from degradation for achieving their functions. To fulfill the complicated task of oral drug delivery, we present a hierarchically structured drug-delivery system that can undertake structural changes, so multiple functions can be triggered by a sequence of stimuli. Such hierarchical system is achieved in a nanoparticle-in-nanofiber configuration, in which both the nanofibers and the nanoparticles are pH-responsive and biocompatible. A model peptide is efficiently encapsulated under mild condition, and the nanocarriers are further electrospun with a pH-responsive mucoadhesive polymer. The nanoparticles are released from the nanofibers, and thereafter the peptides are released from the nanoparticles in a pH-responsive manner. The nanoparticles are compatible with caco-2 cells, and the endocytosis of the nanoparticles is described in detail.

The Cushion Method: A New Technique for the Recovery of Hydrophilic Nanocarriers

Microencapsulation of hydrophilic therapeutic agents such as proteins or nucleotides into a nanocarrier is frequently accomplished in inverse (water-in-oil) emulsions. However, the redispersion of the nanocarriers in aqueous media often involves a complicated purification process, and the redispersion usually requires additional surfactants for its colloidal stability, which is not favored for biological applications. We propose a simple, fast, and mild method to recover hydrophilic nanocarriers prepared in inverse emulsions by temporary coating of the nanocarriers with biocompatible small molecules, so that the final aqueous dispersion of the nanocarriers can be dispersed with high recovery rate, minimal aggregation, and no additional surfactants. Such a method is termed the "cushion method" and was adopted in the preparation of chitosan nanocarriers. The nanocarriers recovered with the cushion method release encapsulated peptides in a pH-responsive manner and do not require surfactants for colloidal stabilization.

Triggered Release of Encapsulated Cargo from Photoresponsive Polyelectrolyte Nanocomplexes

Combining the numerous advantages of using light as a stimulus, simple free radical random copolymerization, and the easy, all-aqueous preparation of polyelectrolyte complexes (PECs), we prepared photolabile PEC nanoparticles and demonstrated their rapid degradation under UV light. As a proof of concept demonstration, the dye Nile Red was encapsulated in the PECs and successfully released into the surrounding solution as the polyelectrolyte nanocomplex carriers dissolved upon light irradiation.

Stabilization of Inverse Miniemulsions by Silyl-Protected Homopolymers

Inverse (water-in-oil) miniemulsions are an important method to encapsulate hydrophilic payloads such as oligonucleotides or peptides. However, the stabilization of inverse miniemulsions usually requires block copolymers that are difficult to synthesize and/or cannot be easily removed after transfer from a hydrophobic continuous phase to an aqueous continuous phase. We describe here a new strategy for the synthesis of a surfactant for inverse miniemulsions by radical addition⁻fragmentation chain transfer (RAFT) polymerization, which consists in a homopolymer with triisopropylsilyl protecting groups. The protecting groups ensure the efficient stabilization of the inverse (water-in-oil, w/o) miniemulsions. Nanocapsules can be formed and the protecting group can be subsequently cleaved for the re-dispersion of nanocapsules in an aqueous medium with a minimal amount of additional surfactant.

Formation, characterization and release kinetics of chitosan/γ-PGA encapsulated nisin nanoparticles

To improve its efficiency, nisin was encapsulated in a γ-PGA and chitosan nanoparticles using self-assembly method. The release of nisin from the nanoparticles exhibited a pH-dependent pattern, and the release mechanism was an anomalous behavior.