Biocompatible Coatings from Smart Biopolymer Nanoparticles for Enzymatically Induced Drug Release

Spatially and Temporally Controllable BMP-2 and TGF-β3 Double Release From Polycaprolactone Fiber Scaffolds via Chitosan-Based Polyelectrolyte Coatings

Temporally and spatially controlled growth factor release from a polycaprolactone fiber mat, which also provides a matrix for directional cell colonization and infiltration, could be a promising regenerative approach for degenerated tendon-bone junctions. For this purpose, polycaprolactone fiber mats were coated with tailored chitosan-based nanogels to bind and release the growth factors bone morphogenetic protein 2 (BMP-2) and transforming growth factor-β3 (TGF-β3), respectively. In this work we provide meaningful in vitro data for the understanding of the drug delivery performance and sterilizability of novel implant prototypes in order to lay the foundation for in vivo testing. ELISA-based in vitro release studies were used to investigate the spatial and temporal control of release, as well as the influence of radiation sterilization on protein activity and release behavior. Layer-by-layer coatings based on BMP-2-containing chitosan tripolyphosphate nanogel particles and negatively charged alginate showed a good sustainment of BMP-2 release from chemically modified polycaprolactone fiber mats. Release control improved with increasing layer numbers. The approach of controlling the release via a barrier of cross-linked chitosan azide proved less promising. By using a simple, partial immersion-based dip-coating process, it was possible to apply opposing gradients of the growth factors BMP-2 and TGF-β3. Final radiation sterilization of the growth factor-loaded implant prototypes resulted in a radiation dose-correlated degradation of the growth factors, which could be prevented by lyophilization into protective matrices. For the manufacture of sterile implants, the growth factor loading step must probably be carried out under aseptic conditions. The layer-by-layer coated implant prototypes provided sustained release from opposing gradients of the growth factors BMP-2 and TGF-β3 and thus represent a promising approach for the restoration of tendon-bone defects.

Progress in Surface Modification of Titanium Implants by Hydrogel Coatings

Although titanium and titanium alloys have become the preferred materials for various medical implants, surface modification technology still needs to be strengthened in order to adapt to the complex physiological environment of the human body. Compared with physical or chemical modification methods, biochemical modification, such as the introduction of functional hydrogel coating on implants, can fix biomolecules such as proteins, peptides, growth factors, polysaccharides, or nucleotides on the surface of the implants, so that they can directly participate in biological processes; regulate cell adhesion, proliferation, migration, and differentiation; and improve the biological activity on the surface of the implants. This review begins with a look at common substrate materials for hydrogel coatings on implant surfaces, including natural polymers such as collagen, gelatin, chitosan, and alginate, and synthetic materials such as polyvinyl alcohol, polyacrylamide, polyethylene glycol, and polyacrylic acid. Then, the common construction methods of hydrogel coating (electrochemical method, sol-gel method and layer-by-layer self-assembly method) are introduced. Finally, five aspects of the enhancement effect of hydrogel coating on the surface bioactivity of titanium and titanium alloy implants are described: osseointegration, angiogenesis, macrophage polarization, antibacterial effects, and drug delivery. In this paper, we also summarize the latest research progress and point out the future research direction. After searching, no previous relevant literature reporting this information was found.

Functionalized Moringa oleifera Gum as pH-Responsive Nanogel for Doxorubicin Delivery: Synthesis, Kinetic Modelling and In Vitro Cytotoxicity Study

Environment-responsive-cum-site-specific delivery of therapeutic drugs into tumor cells is a foremost challenge for chemotherapy. In the present work, Moringa oleifera gum-based pH-responsive nanogel (MOGN) was functionalized as a doxorubicin (DOX) carrier. It was synthesized via free radical polymerization through the γ-irradiation method using acrylamide and N,N'-MBA followed by hydrolysis, sonication, and ultracentrifugation. The swelling behavior of MOGN as a function of pH was assessed using a gravimetric method that revealed its superabsorbent nature (365.0 g/g). Furthermore, MOGN showed a very high loading efficiency (98.35 %L) of DOX by MOGN. In vitro release studies revealed that DOX release from DOX-loaded MOGN was 91.92% at pH 5.5 and 12.18% at 7.4 pH, thus favorable to the tumor environment. The drug release from nanogel followed Korsmeyer-Peppas model at pH 5.5 and 6.8 and the Higuchi model at pH 7.4. Later, the efficient DOX release at the tumor site was also investigated by cytotoxicity study using Rhabdomyosarcoma cells. Thus, the synthesized nanogel having high drug loading capacity and excellent pH-triggered disintegration and DOX release performance in a simulated tumor environment could be a promising candidate drug delivery system for the targeted and controlled release of anticancer drugs.

Enzyme-Responsive Nanoparticles and Coatings Made from Alginate/Peptide Ciprofloxacin Conjugates as Drug Release System

Infection-controlled release of antibacterial agents is of great importance, particularly for the control of peri-implant infections in the postoperative phase. Polymers containing antibiotics bound via enzymatically cleavable linkers could provide access to drug release systems that could accomplish this. Dispersions of nanogels were prepared by ionotropic gelation of alginate with poly-l-lysine, which was conjugated with ciprofloxacin as model drug via a copper-free 1,3-dipolar cycloaddition (click reaction). The nanogels are stable in dispersion and form films which are stable in aqueous environments. However, both the nanogels and the layers are degraded in the presence of an enzyme and the ciprofloxacin is released. The efficacy of the released drug against Staphylococcus aureus is negatively affected by the residues of the linker. Both the acyl modification of the amine nitrogen in ciprofloxacin and the sterically very demanding linker group with three annellated rings could be responsible for this. However the basic feasibility of the principle for enzyme-triggered release of drugs was successfully demonstrated.

Neutrophils exhibit an individual response to different oral bacterial biofilms

Oral innate immunity is led by neutrophils. It is still unclear how their main antimicrobial mechanisms against different biofilms may contribute to balance or dysregulation in the oral cavity. We investigated the capacity of commensal (Streptococcus oralis) and pathogenic (Porphyromonas gingivalis or Aggregatibacter actinomycetemcomitans) monospecies biofilms to induce or to inhibit selected antimicrobial mechanisms of neutrophils. S. oralis induced neutrophil extracellular traps (NETs) formation, reactive oxygen species (ROS) production, and matrix metalloproteinases (MMPs) 8 and 9 secretion. However, these responses were partially reduced in PMA-activated neutrophils indicating a balance-like neutrophil response, which might be important for the maintenance of oral health. P. gingivalis generally induced ROS. Reduced NET formation and significantly decreased MMP secretion were detectable in activated neutrophils highlighting P. gingivalis’ nucleolytic and proteolytic activity, which might support bacterial colonization and pathogenesis of periodontitis. In contrast, A. actinomycetemcomitans did not affect the levels of antimicrobial factors in activated neutrophils and induced NET formation, ROS production, and secretion of MMP-8 and -9 in neutrophils alone, which might contribute to tissue destruction and disease progression. In summary, neutrophil responses to biofilms were species-specific and might support either maintenance of oral health or pathogenesis of periodontitis depending on the species.

Enzyme Degradable Polymersomes from Chitosan-g-[poly-l-lysine-block-ε-caprolactone] Copolymer

The scope of this study includes the synthesis of chitosan-g-[peptide-poly-ε-caprolactone] and its self-assembly into polymeric vesicles employing the solvent shift method. In this way, well-defined core-shell structures suitable for encapsulation of drugs are generated. The hydrophobic polycaprolactone side-chain and the hydrophilic chitosan backbone are linked via an enzyme-cleavable peptide. The synthetic route involves the functionalization of chitosan with maleimide groups and the preparation of polycaprolactone with alkyne end-groups. A peptide functionalized with a thiol group on one side and an azide group on the other side is prepared. Thiol-ene click-chemistry and azide-alkyne Huisgen cycloaddition are then used to link the chitosan and poly-ε-caprolactone chains, respectively, with this peptide. For a preliminary study, poly-l-lysin is a readily available and cleavable peptide that is introduced to investigate the feasibility of the system. The size and shape of the polymersomes are studied by dynamic light scattering and cryo-scanning electron microscopy. Furthermore, degradability is studied by incubating the polymersomes with two enzymes, trypsin and chitosanase. A dispersion of polymersomes is used to coat titanium plates and to further test the stability against enzymatic degradation.

Sustained in vitro interferon-beta release and in vivo toxicity of PLGA and PEG-PLGA nanoparticles

Interferon-beta-1a (IFN-β-1a) can diminish the symptoms of relapsing-remitting multiple sclerosis. Herein, we prepared sustained drug delivery IFN-β-1a-loaded nanoparticles by a double emulsion solvent evaporation method. Bovine serum albumin (BSA) model drug was used to optimize the preparation of nanoparticles composed of four types of poly(lactic-co-glycolic acid) (PLGA) polymers and two pegylated PLGA (PEG-PLGA) polymers. Via optimization, selected PLGA and PEG-PLGA polymers were able to entrap IFN-β-1a with high encapsulation efficiency (>95%) and low size (145 nm and 163 nm, respectively). In vitro release kinetics of BSA and IFN-β showed similar tendency for PLGA and PEG-PLGA nanoparticles, respectively. Although the drug loaded nanoparticles did not show toxicity in hepatocyte cells, mild toxic effects such as pale kidney and pyelectasis were observed in the in vivo studies.

Chitosan-Azide Nanoparticle Coating as a Degradation Barrier in Multilayered Polyelectrolyte Drug Delivery Systems

Therapeutics, proteins or drugs, can be encapsulated into multilayer systems prepared from chitosan (CS)/tripolyphosphat (TPP) nanogels and polyanions. Such multilayers can be built-up by Layer-by-Layer (LbL) deposition. For use as drug-releasing implant coating, these multilayers must meet high requirements in terms of stability. Therefore, photochemically crosslinkable chitosan arylazide (CS–Az) was synthesized and nanoparticles were generated by ionotropic gelation with TPP. The particles were characterized with regard to particle size and stability and were used to form the top-layer in multilayer films consisting of CS–TPP and three different polysaccharides as polyanions, namely alginate, chondroitin sulfate or hyaluronic acid, respectively. Subsequently, photo-crosslinking was performed by irradiation with UV light. The stability of these films was investigated under physiological conditions and the influence of the blocking layer on layer thickness was investigated by ellipsometry. Furthermore, the polyanion and the degree of acetylation (DA) of chitosan were identified as additional parameters that influence the film structure and stability. Multilayer systems blocked with the photo-crosslinked chitosan arylazide showed enhanced stability against degradation.