Prilling of API/fatty acid suspensions: Screening of additives for drug release modification

Current study screened additives which could modify the drug release from prills made of an active pharmaceutical ingredient/fatty acid (API/FA) suspension, without negatively influencing the processability and/or stability of the formulation. Therefore, 11 additives (i.e. emulsifiers, pore-formers and FA-based lubricants) were added in a 20% concentration to a paracetamol/behenic acid formulation. Two additives, Kolliphor® P338 and P407 provided complete drug release in less than 1 h, as their thermoreversible gel formation resulted in a disintegration of the prills. Lower Kolliphor® P338 or P407 concentrations (2.5-10%) resulted in a complete but slower drug release in 24 h as the prills no longer disintegrated and the release mechanism was dominated by pore-formation. Prills with a robust drug release profile (i.e. independent of pH and surfactant concentration of the dissolution medium) were obtained after the addition of ≥5% Kolliphor® P338 or P407 to the FA-based formulation. Based on a 6-month stability study, it was concluded that Kolliphor® P407 was a suitable additive to modify the drug release profile of API/FA suspension-based prills when formulations were stored below 25 °C at low relative humidity.

Prilling of API/fatty acid suspensions: Processability and characterisation

Current study evaluated the processability and characteristics of prills made of an active pharmaceutical ingredient/fatty acid (API/FA) suspension instead of previously studied API/FA solutions to enlarge the application field of prilling. Metformin hydrochloride (MET) and paracetamol (PAR) were used as model APIs while both the effect of drug load (10-40%) and FA chain length (C14-C22) were evaluated. API/FA suspensions were processable on lab-scale prilling equipment without thermal degradation, nozzle obstruction or sedimentation in function of processing time. The collected prills were spherical (AR ≥ 0.898) with a smooth surface (sphericity ≥ 0.914) and a particle size of ±2.3 mm and 2.4 mm for MET and PAR prills, respectively, independent of drug load and/or FA chain length. In vitro drug release evaluation revealed a faster drug release at higher drug load, higher API water solubility and shorter FA chain length. Solid state characterisation via XRD and Raman spectroscopy showed that API and FA crystallinity was maintained after thermal processing via prilling and during storage. Evaluation of the similarity factor indicated a stable drug release (f₂ > 50) from MET and PAR prills after 6 months storage at 25 °C or 40 °C.

Thermoplastic polyurethane-based intravaginal rings for prophylaxis and treatment of (recurrent) bacterial vaginosis

The aim of the present study was to develop thermoplastic polyurethane (TPU)-based intravaginal rings (IVRs) for prophylaxis and treatment of bacterial vaginosis via hot melt extrusion/injection molding. Therefore, different TPU grades were processed in combination with lactic acid or metronidazole, targeting a sustained lactic acid release over a 28day-period and sustained metronidazole release over 4-7days. Hot melt extrusion of lactic acid/TPU combinations required a lower extrusion temperature due to the plasticizing properties of lactic acid, evidenced by the lower glass transition temperature (T_g) and cross-over point (T_tanδ=1) values. NIR-chemical imaging data showed a homogenous distribution of lactic acid in TPU matrices at drug loads up to 30% (w/w). The addition of metronidazole did not lower processing temperatures, as the active pharmaceutical ingredient remained crystalline in the TPU matrix. Hydrophobic TPUs with a low ratio between the soft and hard segments (SS/HS ratio) in the polymer structure were suitable carriers for the lactic acid-eluting device over a 28-day period, while hydrophilic TPUs were needed to achieve the required release rate of metronidazole-eluting IVRs. IVRs manufactured with a TPU grade having a higher SS/HS ratio and lactic acid/TPU ratio exhibited a more elastic behavior. The addition of 25% (w/w) metronidazole did not affect the mechanical properties of the IVRs. Hydrophilic TPUs were most prone to biofilm formation by Candida albicans and Staphylococcus aureus, but the incorporation of metronidazole in the device prevented biofilm formation. Based on the drug eluting performance and mechanical tests, a mixture of lactic acid and Tecoflex™ EG-93A (20/80, w/w) and a combination of metronidazole and Tecophilic™ SP-93A-100 (25/75, w/w) were selected to design IVRs for the prophylaxis and treatment of bacterial vaginosis, respectively. Slug mucosal irritation tests predicted low irritation potency for both devices.

Influenza-binding sialylated polymer coated gold nanoparticles prepared via RAFT polymerization and reductive amination

We report on a straightforward strategy to fabricate bioactive glycosylated gold nanoparticles via a combination of RAFT polymerization, carbohydrate ligation through reductive amination and thiol-gold self-assembly. This approach is used for the design of gold nanoparticles decorated with the complex sialylated glycan Neu5Ac-α-2-6-Gal, and we demonstrate multivalent and specific recognition between the nanoparticles, lectins and hemagglutinin on the surface of the influenza virus.

Correction: Polymer–protein conjugation via a ‘grafting to’ approach – a comparative study of the performance of protein-reactive RAFT chain transfer agents

Correction for ‘Polymer–protein conjugation via a ‘grafting to’ approach – a comparative study of the performance of protein-reactive RAFT chain transfer agents’ by N. Vanparijs et al., Polym. Chem., 2015, DOI: 10.1039/c4py01224k.

Polymer-protein conjugation via a ‘grafting to’ approach – a comparative study of the performance of protein-reactive RAFT chain transfer agents

The performances of various protein-reactive RAFT CTAs to afford polymer-protein conjugation via a grafting-to approach were compared.

Transiently responsive protein–polymer conjugates via a ‘grafting-from’ RAFT approach for intracellular co-delivery of proteins and immune-modulators

‘Grafting-from’ RAFT polymerization is used to synthesize protein–polymer conjugates that change from the soluble to the aggregated state in response to temperature, but become fully soluble by acid triggered hydrolysis.

Targeting aminopeptidase N, a newly identified receptor for F4ac fimbriae, enhances the intestinal mucosal immune response

Enterotoxigenic Escherichia coli (ETEC) are a major cause of diarrhea in human and animal. In piglets, ETEC having F4 fimbriae (F4(+) ETEC) induce severe diarrhea, dependent on the presence of receptors for F4 (F4R). In this study, porcine aminopeptidase N (pAPN) was identified as an F4R by comparative proteomic analysis of brush border proteins of F4R(+) and F4R(-) pigs and by adherence/internalization experiments on pAPN-transfected cells. Binding of F4 fimbriae to pAPN depended on sialic acid containing carbohydrate moieties, and resulted in clathrin-mediated endocytosis of the fimbriae. Endocytosis via pAPN was not restricted to F4 fimbriae, but was also observed for anti-pAPN antibodies. Both F4 fimbriae- and pAPN-specific antibodies were taken up in vivo by porcine enterocytes and induced subsequently a rapid immunoglobulin A and G response. In conclusion, we identified pAPN as an endocytotic receptor for F4 fimbriae and highlight the opportunity to target vaccine antigens to this epithelial receptor.

Patchiness of embedded particles and film stiffness control through concentration of gold nanoparticles

Patchy particles are fabricated using a method of embedding-into and extracting-from thick, biocompatible, gel-like HA/PLL films. Control over the patchiness is achieved by adjusting the stiffness of films, which affects embedding and masking of particles. The stiffness is adjusted by the concentration of gold nanoparticles adsorbed onto the surface of the films.

Layer-by-layer coating of degradable microgels for pulsed drug delivery

Recently, we reported on "self-rupturing" microcapsules which consist of a biodegradable dextran-based microgel surrounded by a polyelectrolyte membrane. Degradation of the microgel increases the swelling pressure in the microcapsules which, when sufficiently high, ruptures the surrounding polyelectrolyte membrane. The membrane surrounding the microgels is deposited using the layer-by-layer (LbL) technique, which is based on the alternate adsorption of oppositely charged polyelectrolytes onto a charged substrate. In this paper, we characterize with confocal microscopy, electrophoretic mobility, scanning electron microscopy and atomic force microscopy in detail the deposition and the properties of the LbL coatings on the dextran microgels. We show that by fine-tuning the properties of both the microgel core and the LbL membrane the swelling pressure which is evoked by the degradation of the microgel is indeed able to rupture the surrounding LbL membrane. Further, we show that the application of an LbL coating on the surface of the microgels dramatically lowers the burst release from the microcapsules and results in massive release at the time the microcapsules rupture.