Evaluation of Physicochemical Properties Following Syringe-to-Syringe Mixing of Hyaluronic Acid Dermal Fillers.

BACKGROUND: Historically, soft-tissue hyaluronic acid (HA) fillers have been mixed with agents to reduce pain or alter physicochemical properties. OBJECTIVE: Evaluate the impact of dilution and mixing on HA filler physicochemical properties. MATERIALS AND METHODS: Crosslinked HA filler (VYC-20L, 20 mg/mL) was diluted to 15 mg/mL using saline through 5 or 10 passes between 2 syringes connected using a luer connector. Extrusion force, rheological properties, and microscopic appearance were assessed. Undiluted VYC-15L (15 mg/mL) served as the control. RESULTS: Average extrusion force was higher for diluted VYC-20L versus the control, with an increase in slope for gel diluted using 5 passes (0.65) and 10 passes (0.52) versus the control (<0.1). For diluted samples mixed with 5 or 10 passes, the rheological profile was different between the 2 halves of the syringe, with the second half more elastic than the first half, compared with the consistent profile of undiluted samples. Microscopically, diluted VYC-20L samples seemed more liquid near the luer and more particulate near the piston compared with the control, which was smooth throughout. CONCLUSION: In addition to potentially introducing contamination, diluting or mixing soft-tissue HA fillers yields a heterogeneous product with physicochemical characteristics that vary substantially throughout the syringe.

Acid-degradable polymers for drug delivery: a decade of innovation.

Polymers that start degrading under acidic conditions are increasingly investigated as a pathway to trigger the release of drugs once the drug carrier reached the slightly acidic tumour environment or after the drug carrier has been taken up by cells, resulting in the localization of the polymer in the acidic endosomes and lysosomes. The advances in the design of acid-degradable polymers and drug delivery systems have been summarized and discussed in this review article. Various acid-labile groups such as acetals, orthoester, hydrazones, imines and cis-aconityl, that can undergo cleavage in slightly acidic conditions, have been employed to create polymer architectures or polymer-drug conjugates that can degrade under lysosomal and endosomal conditions, triggering the fast release of drugs or DNA.

Zwitterionic guanidine-based oligomers mimicking cell-penetrating peptides as a nontoxic alternative to cationic polymers to enhance the cellular uptake of micelles.

The aim of this work is to generate polymer micelles decorated with a synthetic version of cell-penetrating peptides, which are often rich in arginine with its positively charged guanidine group. A methacrylate-based monomer with guanidinium as functional groups was prepared using arginine (M-Arg) as a building block, resulting in a zwitterionic monomer. RAFT (reversible addition-fragmentation chain transfer) polymerization was employed to generate triblock copolymers with poly(methyl methacrylate)-block-poly(polyethylene glycol methyl ether methacrylate) as the first two blocks, which were subsequently chain extended with the guanidine-based monomer to generate micelles with guanidinium functional groups on the surface. To simulate the actual oligoarginine peptide, which only carries cationic charges, the carboxylate group of P(M-Arg) was methylated to convert the zwitterionic polymer into a cationic polymer P(Me-M-Arg). For comparison, micelles based on triblock copolymers with a third block with permanently cationic charges, poly(2-methacryolyloxy ethyl) trimethyl ammonium chloride (PTMA), was prepared. The hydrodynamic diameters of the micelles were approximately 30-40 nm based on DLS and TEM. A direct correlation between surface charge (zeta potential ζ) and cytotoxicity was observed. The micelles based on the zwitterionic P(M-Arg) were nontoxic (ζ = -10 mV at pH = 7), while the methylated version P(Me-M-Arg) with a high cationic charge (ζ = +35 mV at pH = 7) were observed to be toxic. The cellular uptake of the block copolymers by OVCAR-3 ovarian cancer cell lines was found to be relatively fast (about 35% in 3 min) reaching an equilibrium after approximately 30 min. Both micelles, with either P(M-Arg) or P(Me-M-Arg) on the surface, showed an enhanced uptake compared to micelles with P(PEGMEMA) as shell only. In fact, the percentage of uptake was similar, with the difference that cells incubated with micelles with P(M-Arg) (zwitterionic) stayed alive, while P(Me-M-Arg) (cationic) led to significant cell death.

Shell cross-linking of cyclodextrin-based micelles via supramolecular chemistry for the delivery of drugs.

A block copolymer based on poly(N-isopropyl acrylamide) (PNIPAAm) and a block with a statistical distribution of poly(2-hydroxyethyl acrylate) (PHEA) and repeating unit with carrying ß-cyclodextrin was prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization and click reaction. Addition of poly(2-hydroxyethyl acrylate-s-adamantylmethyl acrylate) P(HEA(17) -s-AdMA(7) ) above the LCST of the block copolymer led to capture of the micelle structure of 36 nm against disassembly. The drug- (albendazole) loaded supramolecular assembly, which was fixed via host-guest complexation between ß-cyclodextrin and adamantane, was then tested as a drug carrier. Cell viability studies using human ovarian carcinoma cell line (OVCAR-3) cell lines show a higher toxicity of the shell cross-linked micelle compared with the free block copolymer.

Precise synthesis of molecularly defined oligomers and polymers by orthogonal iterative divergent/convergent approaches.

The synthesis of perfectly defined (macro)molecules has been a constant challenge for polymer and organic chemists. This paper highlights the main applications of the iterative divergent/convergent approach for the synthesis of discrete mass oligomers and polymers. We will discuss the orthogonal deprotection and coupling strategies involved in this powerful strategy where chain length doubles at each iteration and which has been applied to the synthesis of conjugated rigid rods as well as amorphous and crystalline oligomers and polymers. The synthesis of perfectly defined oligomers in respect to emerging highly efficient and orthogonal chemistries will also be highlighted.

Click chemistry step growth polymerization of novel alpha-azide-omega-alkyne monomers.

A novel step growth polymerization A-B strategy based on the click chemistry polyaddition of tailor-made alpha-azide-omega-alkyne low molar mass monomers was developed, leading to polytriazole (co)polymers with tunable structures and properties.