Preparation of Polymeric Prodrug Paclitaxel-Poly(lactic acid)-b-Polyisobutylene and Its Application in Coatings of a Drug Eluting Stent

3D Printing of Triamcinolone Acetonide in Triblock Copolymers of Styrene–Isobutylene–Styrene as a Slow-Release System

Additive manufacturing has a wide range of applications and has opened up new methods of drug formulation, in turn achieving attention in medicine. We prepared styrene–isobutylene–styrene triblock copolymers (SIBS; Mn = 10 kDa–25 kDa, PDI 1,3–1,6) as a drug carrier for triamcinolone acetonide (TA), further processed by fused deposition modeling to create a solid drug release system displaying improved bioavailability and applicability. Living carbocationic polymerization was used to exert control over block length and polymeric architecture. Thermorheological properties of the SIBS polymer (22.3 kDa, 38 wt % S) were adjusted to the printability of SIBS/TA mixtures (1–5% of TA), generating an effective release system effective for more than 60 days. Continuous drug release and morphological investigations were conducted to probe the influence of the 3D printing process on the drug release, enabling 3D printing as a formulation method for a slow-release system of Triamcinolone.

Synthesis of linear and star-shaped telechelic polyisobutylene by cationic polymerization

Hydroxyl-terminated linear and star-shaped telechelic polyisobutylene have been successfully synthesized by living cationic polymerization using propylene oxide (PO)/Titanium tetrachloride (TiCl₄) as the initiator system. A one-step method to prepare the terminal hydroxyl group was realized by selecting the cheap and beautiful epoxide as the functional initiator, which has the prospect of industrial application. The polymerization mechanism was proposed by the end structure analysis and Gaussian calculation results. At the same time, the living linear macromolecular chain was used as the starting point to react with divinyl compounds for synthesis of star-shaped hydroxyl-terminated polyisobutylene. The effects of initiator-crosslinking agent ratio, arm length, and reaction time on the coupling reaction were studied.

Hydroxyl-terminated linear and star-shaped telechelic polyisobutylene have been successfully synthesized by living cationic polymerization using propylene oxide (PO)/Titanium tetrachloride (TiCl₄) as the initiator system.

Body temperature polymerization and in situ drug encapsulation in supercritical carbon dioxide

Body-temperature and solvent-free polymerization and in situ fabrication of drug-loaded microparticles are reported for the first time.

Design of diffusion-controlled drug delivery devices for controlled release of Paclitaxel

Controlled drug delivery devices were predicted in a reverse engineering framework for the controlled release of Paclitaxel, an anti-cancer drug, widely used in the treatment of solid tumors. Using quantitative structure-property relationship models for mutual diffusion coefficients of the drug in biocompatible and biodegradable polymers and partition coefficients of the drug between polymers and blood, a framework was developed to predict optimal drug delivery devices for desired dosage regimens. The validation of the predicted mutual diffusion and partition coefficients using experimental data was reported in previous studies. Optimal design parameters along with selection of most appropriate polymers suitable for different dosage regimens, selected based on current clinical practice, were predicted for maximum bioavailability of the drug while maintaining the released drug concentration in blood within the therapeutic range. Reservoir and monolithic type of diffusion-controlled drug delivery devices of different shapes and sizes were predicted with different initial drug loadings and bioavailability for different dosage regimens. The effects of the released Paclitaxel from these devices on the tumor growth were also modeled using a previously reported mathematical pharmacokinetic-pharmacodynamic model. The proposed approach can easily be used to design other diffusion-controlled drug delivery devices.

A dual responsive hyaluronic acid graft poly(ionic liquid) block copolymer micelle for an efficient CD44-targeted antitumor drug delivery

Illustration of the formation and elevated antitumor mechanism of the HA-g-mPEG-polymers nanocarriers.

Controlled organocatalyzed d,l-lactide ring-opening polymerizations: synthesis of low molecular weight oligomers

A systematic approach to the synthesis of organocatalyzed oligo(d,l-lactide) demonstrates that choice of initiator, catalytic ratio, and reaction time yields well-controlled oligomers. Ring-opening polymerization of d,l-lactide with the initiator α-methyl propargyl alcohol, a secondary alcohol, used in excess of 4-dimethylaminopyridine catalyst mitigates cyclicization, transesterification, and catalyst-initiated side reactions. This approach enables the design of uniform lactide oligomers for controlled release applications, such as delivery systems for drugs, prodrugs, and molecular sensors.

Thiol-substituted copolylactide: synthesis, characterization and post-polymerization modification using thiol–ene chemistry

A copolylactide that is substituted with pendent thiol groups (thiol-PL) undergoes coupling with a variety of electrophiles under mild conditions via thiol–ene addition.

Mechanistic applications of click chemistry for pharmaceutical drug discovery and drug delivery

The concept of click chemistry (CC), first introduced by K.B. Sharpless, has been widely adopted for use in drug discovery, novel drug delivery systems (DDS), polymer chemistry, and material sciences. In this review, we outline novel aspects of CC related to drug discovery and drug delivery, with a brief overview of molecular mechanisms underlying each click reaction commonly used by researchers, and the main patents that paved the way for further diverse medicinal applications. We also describe recent progress in drug discovery and polymeric and carbon material-based drug delivery for potential pharmaceutical applications and advancements based on the CC approach, and discuss some intrinsic limitations of this popular conjugation reaction. The use of CC is likely to significantly advance drug discovery and bioconjugation development.

Multicompartment morphologies self-assembled from fluorinated ABC triblock terpolymers: the effects of flexible and rigid hydrophobic moieties

Two kinds of fluorinated ABC triblock terpolymers have been prepared by oxyanion-initiated polymerization, and the effects of flexible and rigid polyolefin moieties on their self-assembled multicompartment morphologies were investigated.

Covalent Polyisobutylene-Paclitaxel Conjugates for Controlled Release from Potential Vascular Stent Coatings

The development of covalent polyisobutylene (PIB)-paclitaxel (PTX) conjugates as a potential approach to controlling drug release from vascular stent coatings is described. PIB-PTX materials containing ∼24 and ∼48 wt % PTX, conjugated via ester linkages, were prepared. The PTX release profiles were compared with those of physical mixtures of PTX with carboxylic acid-functionalized PIB and with the triblock copolymer polystyrene-b-PIB-b-polystyrene (SIBS). Covalent conjugation led to significantly slower drug release. Atomic force microscopy imaging of coatings of the materials suggested that the physical mixtures exhibited multiple domains corresponding to phase separation, whereas the materials in which PTX was covalently conjugated appeared homogeneous. Coatings of the conjugated materials on stainless steel surfaces suffered less surface erosion than the physically mixed materials, remained intact, and adhered well to the surface throughout the thirty-five day study. Tensile testing and rheological studies suggested that the incorporation of PTX into the polymer introduces similar physical changes to the PIB as the incorporation of a glassy polystyrene block does in SIBS. Cytotoxicity assays showed that the coatings did not release toxic levels of PTX or other species into a cell culture medium over a 24 h period, yet the levels of PTX in the materials were sufficient to prevent C2C12 cells from adhering to and proliferating on them. Overall, these results indicate that covalent PIB-PTX conjugates have promise as coatings for vascular stents.