Simultaneous drug release at different rates from biodegradable polyurethane foams

A Novel PAMAM G3 Dendrimer-Based Foam with Polyether Polyol and Castor Oil Components as Drug Delivery System into Cancer and Normal Cells

One of the intensively developed tools for cancer therapy is drug-releasing matrices. Polyamidoamine dendrimers (PAMAM) are commonly used as nanoparticles to increase the solubility, stability and retention of drugs in the human body. Most often, drugs are encapsulated in PAMAM cavities or covalently attached to their surface. However, there are no data on the use of PAMAM dendrimers as a component of porous matrices based on polyurethane foams for the controlled release of drugs and biologically active substances. Therefore, in this work, porous materials based on polyurethane foam with incorporated third-generation poly(amidoamine) dendrimers (PAMAM G3) were synthesized and characterized. Density, water uptake and morphology of foams were examined with SEM and XPS. The PAMAM was liquefied with polyether polyol (G441) and reacted with polymeric 4,4'-diphenylmethane diisocyanate (pMDI) in the presence of silicone, water and a catalyst to obtain foam (PF1). In selected compositions, the castor oil was added (PF2). Analogs without PAMAM G3 were also synthesized (F1 and F2, respectively). An SEM analysis of foams showed that they are composed of thin ribs/walls forming an interconnected network containing hollow bubbles/pores and showing some irregularities in the structure. Foam from a G3:G441:CO (PF2) composition is characterized by a more regular structure than the foam from the composition without castor oil. The encapsulation efficiency of drugs determined by the XPS method shows that it varies depending on the matrix and the drug and ranges from several to a dozen mass percent. In vitro biological studies with direct contact and extract assays indicated that the F2 matrix was highly biocompatible. Significant toxicity of dendrimeric matrices PF1 and PF2 containing 50% of PAMAM G3 was higher against human squamous carcinoma cells than human immortalized keratinocytes. The ability of the matrices to immobilize drugs was demonstrated in the example of perspective (Nimesulide, 8-Methoxypsolarene) or approved anticancer drugs (Doxorubicin-DOX, 5-Aminolevulinic acid). Release into the culture medium and penetration of DOX into the tested SCC-15 and HaCaT cells were also proved. The results show that further modification of the obtained matrices may lead to their use as drug delivery systems, e.g., for anticancer therapy.

Development of miR-26a-activated scaffold to promote healing of critical-sized bone defects through angiogenic and osteogenic mechanisms

Very large bone defects significantly diminish the vascular, blood, and nutrient supply to the injured site, reducing the bone's ability to self-regenerate and complicating treatment. Delivering nanomedicines from biomaterial scaffolds that induce host cells to produce bone-healing proteins is emerging as an appealing solution for treating these challenging defects. In this context, microRNA-26a mimics (miR-26a) are particularly interesting as they target the two most relevant processes in bone regeneration-angiogenesis and osteogenesis. However, the main limitation of microRNAs is their poor stability and issues with cytosolic delivery. Thus, utilising a collagen-nanohydroxyapatite (coll-nHA) scaffold in combination with cell-penetrating peptide (RALA) nanoparticles, we aimed to develop an effective system to deliver miR-26a nanoparticles to regenerate bone defects in vivo. The microRNA-26a complexed RALA nanoparticles, which showed the highest transfection efficiency, were incorporated into collagen-nanohydroxyapatite scaffolds and in vitro assessment demonstrated the miR-26a-activated scaffolds effectively transfected human mesenchymal stem cells (hMSCs) resulting in enhanced production of vascular endothelial growth factor, increased alkaline phosphatase activity, and greater mineralisation. After implantation in critical-sized rat calvarial defects, micro CT and histomorphological analysis revealed that the miR-26a-activated scaffolds improved bone repair in vivo, producing new bone of superior quality, which was highly mineralised and vascularised compared to a miR-free scaffold. This innovative combination of osteogenic collagen-nanohydroxyapatite scaffolds with multifunctional microRNA-26a complexed nanoparticles provides an effective carrier delivering nanoparticles locally with high efficacy and minimal off-target effects and demonstrates the potential of targeting osteogenic-angiogenic coupling using scaffold-based nanomedicine delivery as a new "off-the-shelf" product capable of healing complex bone injuries.

An overview of polyurethane biomaterials and their use in drug delivery

Polyurethanes are a versatile and highly tunable class of materials that possess unique properties including high tensile strength, abrasion and fatigue resistance, and flexibility at low temperatures. The tunability of polyurethane properties has allowed this class of polymers to become ubiquitous in our daily lives in fields as diverse as apparel, appliances, construction, and the automotive industry. Additionally, polyurethanes with excellent biocompatibility and hemocompatibility can be synthesized, enabling their use as biomaterials in the medical field. The tunable nature of polyurethane biomaterials also makes them excellent candidates as drug delivery vehicles, which is the focus of this review. The fundamental idea we aim to highlight in this article is the structure-property-function relationships found in polyurethane systems. Specifically, the chemical structure of the polymer determines its macroscopic properties and dictates the functions for which it will perform well. By exploring the structure-property-function relationships for polyurethanes, we aim to elucidate the fundamental properties that can be tailored to achieve controlled drug release and empower researchers to design new polyurethane systems for future drug delivery applications.

Magnetically Actuated Shape Memory Polymers for On-Demand Drug Delivery

Repeated use of intravenous infusions to deliver drugs can cause nerve damage, pain, and infection. There is an unmet need for a drug delivery method that administers drugs on demand for prolonged use. Here, we developed magnetically responsive shape memory polymers (SMPs) to enhance control over drug release. Iron oxide magnetic nanoparticles (mnps) were synthesized and incorporated into previously developed SMPs to enable magnetically induced shape memory effects that can be activated remotely via the application of an alternating magnetic field. These materials were tested for their shape memory properties (dynamic mechanical analysis), cytocompatibility (3T3 fibroblast viability), and tunable drug delivery rates (UV−VIS to evaluate the release of incorporated doxorubicin, 6-mercaptopurine, and/or rhodamine). All polymer composites had >75% cytocompatibility over 72 h. Altering the polymer chemistry and mnp content provided methods to tune drug release. Namely, linear polymers with higher mnp content had faster drug release. Highly cross-linked polymer networks with lower mnp content slowed drug release. Shape memory properties and polymer/drug interactions provided additional variables to tune drug delivery rates. Polymers that were fixed in a strained secondary shape had a slower release rate compared with unstrained polymers, and hydrophobic drugs were released more slowly than hydrophilic drugs. Using these design principles, a single material with gradient chemistry and dual drug loading was synthesized, which provided a unique mechanism to deliver two drugs from a single scaffold with distinct delivery profiles. This system could be employed in future work to provide controlled release of selected drug combinations with enhanced control over release as compared with previous approaches.

INVESTIGATION OF THE ABILITY TO BIODEGRADABILITY OF POLYURETHANE FOAM COMPOSITE MATERIALS WITH ALBUCID AND THE DYNAMICS OF ALBUCID RELEASE IN VITRO

Studies of biodegradability of polyurethane foam (PUF) composite materials with albucid under the influence of biological medium 199 (BM 199) and saline solution for 2 weeks, 1, 3 and 6 months were conducted. IR spectroscopy, physical-mechanical tests, DSC and TGA before and after incubation in model mediums were investigated. It was found that the influence of BM 199 and saline solution on the structure and properties of composite materials with albucid is similar. According to the results of physical-mechanical studies under the influence of model mediums there are processes of biodegradation which are confirmed by a decrease in adhesive strength after incubation in BM 199 and saline solution. According to IR spectroscopy, biodegradation is accompanied by redistribution of hydrogen bonds of NH groups of the polymer matrix. The results of studies by the DSC method indicate a decrease of Tg and increase of ΔСР of PUF composites with albucid compared to the control, which is associated with increasing of segmental mobility of macromolecules under the influence of model mediums and due to the albucid release from polymer matrix. It was found that PUF and PUF composites with albucid in vitro remain heat-resistant materials, because after incubation in BM 199 and a saline solution there is an increase in T0 and Tmax by the TGA method. Studies of the dynamics of albucid release from the PUF matrix were carried out. It was found that the composite materials are capable to the prolonged release of the drug. The amount of released albucid is 36.0 % on the 60th day of the experiment, which does not exceed the therapeutic dose and has no toxic effects. Therefore, polyurethane foam composite materials with albucid can be proposed as promising materials for use as implants with prolonged action of albucid in ophthalmological surgery.

Drug Carriers: A Review on the Most Used Mathematical Models for Drug Release

Carriers are protective transporters of drugs to target cells, facilitating therapy under each points of view, such as fast healing, reducing infective phenomena, and curing illnesses while avoiding side effects. Over the last 60 years, several scientists have studied drug carrier properties, trying to adapt them to the release environment. Drug/Carrier interaction phenomena have been deeply studied, and the release kinetics have been modeled according to the occurring phenomena involved in the system. It is not easy to define models’ advantages and disadvantages, since each of them may fit in a specific situation, considering material interactions, diffusion and erosion phenomena, and, no less important, the behavior of receiving medium. This work represents a critical review on main mathematical models concerning their dependency on physical, chemical, empirical, or semi-empirical variables. A quantitative representation of release profiles has been shown for the most representative models. A final critical comment on the applicability of these models has been presented at the end. A mathematical approach to this topic may help students and researchers approach the wide panorama of models that exist in literature and have been optimized over time. This models list could be of practical inspiration for the development of researchers’ own new models or for the application of proper modifications, with the introduction of new variable dependency.

Influence of Hard Segment Content and Diisocyanate Structure on the Transparency and Mechanical Properties of Poly(dimethylsiloxane)-Based Urea Elastomers for Biomedical Applications

The effect of hard segment content and diisocyanate structure on the transparency and mechanical properties of soft poly(dimethylsiloxane) (PDMS)-based urea elastomers (PSUs) was investigated. A series of PSU elastomers were synthesized from an aminopropyl-terminated PDMS (M¯n: 16,300 g·mol⁻¹), which was prepared by ring chain equilibration of the monomers octamethylcyclotetrasiloxane (D₄) and 1,3-bis(3-aminopropyl)-tetramethyldisiloxane (APTMDS). The hard segments (HSs) comprised diisocyanates of different symmetry, i.e., 4,4′-methylenebis(cyclohexyl isocyanate) (H₁₂MDI), 4,4′-methylenebis(phenyl isocyanate) (MDI), isophorone diisocyanate (IPDI), and trans-1,4-cyclohexane diisocyanate (CHDI). The HS contents of the PSU elastomers based on H₁₂MDI and IPDI were systematically varied between 5% and 20% by increasing the ratio of the diisocyanate and the chain extender APTMDS. PSU copolymers of very low urea HS contents (1.0–1.6%) were prepared without the chain extender. All PSU elastomers and copolymers exhibited good elastomeric properties and displayed elongation at break values between 600% and 1100%. The PSUs with HS contents below 10% were transparent and became increasingly translucent at HS contents of 15% and higher. The Young’s modulus (YM) and ultimate tensile strength values of the elastomers increased linearly with increasing HS content. The YM values differed significantly among the PSU copolymers depending on the symmetry of the diisocyanate. The softest elastomer was that based on the asymmetric IPDI. The elastomers synthesized from H₁₂MDI and MDI both exhibited an intermediate YM, while the stiffest elastomer, i.e., that comprising the symmetric CHDI, had a YM three-times higher than that prepared with IPDI. The PSUs were subjected to load–unload cycles at 100% and 300% strain to study the influence of HS morphology on 10-cycle hysteresis behavior. At 100% strain, the first-cycle hysteresis values of the IPDI- and H₁₂MDI-based elastomers first decreased to a minimum of approximately 9–10% at an HS content of 10% and increased again to 22–28% at an HS content of 20%. A similar, though less pronounced, trend was observed at 300% strain. First-cycle hysteresis among the PSU copolymers at 100% strain was lowest in the case of CHDI and highest in the IPDI-based elastomer. However, this effect was reversed at 300% strain, with CHDI displaying the highest hysteresis in the first cycle. In vitro cytotoxicity tests performed using HaCaT cells did not show any adverse effects, revealing their potential suitability for biomedical applications.

Development of Porous Polyurethane Implants Manufactured via Hot-Melt Extrusion

Implantable drug delivery systems (IDDSs) offer good patient compliance and allow the controlled delivery of drugs over prolonged times. However, their application is limited due to the scarce material selection and the limited technological possibilities to achieve extended drug release. Porous structures are an alternative strategy that can overcome these shortcomings. The present work focuses on the development of porous IDDS based on hydrophilic (HPL) and hydrophobic (HPB) polyurethanes and chemical pore formers (PFs) manufactured by hot-melt extrusion. Different PF types and concentrations were investigated to gain a sound understanding in terms of extrudate density, porosity, compressive behavior, pore morphology and liquid uptake. Based on the rheological analyses, a stable extrusion process guaranteed porosities of up to 40% using NaHCO3 as PF. The average pore diameter was between 140 and 600 µm and was indirectly proportional to the concentration of PF. The liquid uptake of HPB was determined by the open pores, while for HPL both open and closed pores influenced the uptake. In summary, through the rational selection of the polymer type, the PF type and concentration, porous carrier systems can be produced continuously via extrusion, whose properties can be adapted to the respective application site.

A 3D printed drug delivery implant formed from a dynamic supramolecular polyurethane formulation

Prototype drug eluting implants have been 3D printed using a supramolecular polyurethane-PEG formulation. The implants are capable of releasing a pharmaceutical active with effective drug release over a period of up to 8.5 months.

Biodegradable ciprofloxacin-incorporated waterborne polyurethane polymers prevent bacterial biofilm formation in vitro

The aim of the present study was to explore whether ciprofloxacin-incorporated waterborne polyurethane (WBPU) polymers have the capacity to inhibit bacterial biofilm formation in vitro. WBPU polymers were incorporated with ciprofloxacin and were cultured with Escherichia coli (E. coli) or Staphylococcus aureus (S. aureus) in media for 2, 4 or 7 days. In another experiment, the WBPU membranes were cultured with Proteus mirabilis (P. mirabilis) in artificial urine for 2, 4 or 7 days. Colony counting, scanning electron microscopy and fluorescence confocal microscopy were utilized to examine bacterial biofilms on the surfaces of membranes. The membranes were further co-cultured with P. mirabilis in a simple model of an artificial catheterized bladder in order to evaluate their ability to control encrustation. The WBPU films with ciprofloxacin effectively inhibited bacterial biofilm formation in the culture medium and in artificial urine. In addition, in artificial urine, the films with ciprofloxacin reduced catheter obstruction. In conclusion, ciprofloxacin-incorporated WBPU polymers are able to effectively inhibit bacterial biofilm formation in vitro.

Polyurethane Foams: Past, Present, and Future

Polymeric foams can be found virtually everywhere due to their advantageous properties compared with counterparts materials. Possibly the most important class of polymeric foams are polyurethane foams (PUFs), as their low density and thermal conductivity combined with their interesting mechanical properties make them excellent thermal and sound insulators, as well as structural and comfort materials. Despite the broad range of applications, the production of PUFs is still highly petroleum-dependent, so this industry must adapt to ever more strict regulations and rigorous consumers. In that sense, the well-established raw materials and process technologies can face a turning point in the near future, due to the need of using renewable raw materials and new process technologies, such as three-dimensional (3D) printing. In this work, the fundamental aspects of the production of PUFs are reviewed, the new challenges that the PUFs industry are expected to confront regarding process methodologies in the near future are outlined, and some alternatives are also presented. Then, the strategies for the improvement of PUFs sustainability, including recycling, and the enhancement of their properties are discussed.

In situ foamable, degradable polyurethane as biomaterial for soft tissue repair

Degradable foams which can be inserted endoscopically as liquid or pasty mixtures into soft tissue defects possess a promising potential for the surgical treatment of such defects. The defects can be sealed under in situ foaming and simultaneous material expansion. We developed an in situ foamable (l-lactide-co-ε-caprolactone)-based, star-shaped prepolymer by ring opening polymerization of l-lactide and ε-caprolactone in the presence of meso-erythritol as starter. By conversion of the terminal hydroxyl groups of the formed oligoester with lysine diisocyanate ethyl ester (LDI) an isocyanate-endcapped, reactive prepolymer has been received. Foaming can be initiated by addition of 1,4-diazabicyclo[2,2,2]octane (DABCO), water, LDI and DMSO. By varying the composition of these additives, the foaming and curing time could be varied within a clinically acceptable range. A porosity of approximately 90%, and an average tensile strength of 0.3MPa with elongations of 90% were determined for the foams. In vitro cytotoxicity on cured foams was assayed on 3T3 fibroblasts and demonstrated an excellent cytocompatibility. This was also confirmed in an in vivo study using an established rat model, where prefabricated foams and in situ hardening material were inserted into subdermal skin incisions in parallel. The feature of chronic inflammation was only weakly developed in both groups and slightly more pronounced and persisted for longer time in the group of in situ foamed material. In both groups the foreign materials were vascularized, degraded and substituted by connective tissue. The results encourage to proceed with trials where the materials are used to fill more heavily loaded defects.

X-ray visible and doxorubicin-loaded beads based on inherently radiopaque poly(lactic acid)-polyurethane for chemoembolization therapy

The aim of current study was to develop drug-loaded polymeric beads with intrinsic X-ray visibility as embolic agents, targeting for noninvasive intraoperative location and postoperative examination during chemoembolization therapy. To endow polymer with inherent radiopacity, 4,4'-isopropylidinedi-(2,6-diiodophenol) (IBPA) was firstly synthesized and employed as a contrast agent, and then a set of radiopaque iodinated poly(lactic acid)-polyurethanes (I-PLAUs) via chain extender method were synthesized and characterized. These I-PLAU copolymers possessed sufficient radiopacity, in vitro non-cytotoxicity with human adipose-derived stem cells, and in vivo biocompatibility and degradability in rabbit model via intramuscular implantation. Doxorubicin (DOX), as a chemotherapeutic agent, was further incorporated into I-PLAU beads via a double emulsification (W/O/W) method. For drug release, two ratios of DOX-loaded I-PLAU beads exhibited calibrated size (200-550μm), porous internal structure, good X-ray visibility, evenly drug loading as well as tunable drug release. A preliminary test on in vitro tumor cell toxicity demonstrated that the DOX-loaded I-PLAU beads performed efficient anti-tumor effect. This study highlights novel X-ray visible drug-loaded I-PLAU beads used as promising embolic agents for non-invasive in situ X-ray tracking and efficient chemotherapy, which could bring opportunities to the next generation of multifunctional embolic agents.

Biodegradable shape memory polymers functionalized with anti-biofouling interpenetrating polymer networks

A novel type of shape memory polyurethane (SMPU) with high mechanical properties and biodegradability was constructed using a lactone copolymer (poly(ε-caprolactone-co-γ-butyrolactone), PCLBL), a diol- or triol-based chain extender (1,5-pentanediol, glycerol and 2-amino-2-hydroxymethyl-1,3-propanediol) and a diisocyanate cross-linker (1,6-hexamethylene diisocyanate).

Injectable foams for regenerative medicine

The design of injectable biomaterials has attracted considerable attention in recent years. Many injectable biomaterials, such as hydrogels and calcium phosphate cements (CPCs), have nanoscale pores that limit the rate of cellular migration and proliferation. While introduction of macroporosity has been suggested to increase cellular infiltration and tissue healing, many conventional methods for generating macropores often require harsh processing conditions that preclude their use in injectable foams. In recent years, processes such as porogen leaching, gas foaming, and emulsion-templating have been adapted to generate macroporosity in injectable CPCs, hydrogels, and hydrophobic polymers. While some of the more mature injectable foam technologies have been evaluated in clinical trials, there are challenges remaining to be addressed, such as the biocompatibility and ultimate fate of the sacrificial phase used to generate pores within the foam after it sets in situ. Furthermore, while implantable scaffolds can be washed extensively to remove undesirable impurities, all of the components required to synthesize injectable foams must be injected into the defect. Thus, every compound in the foam must be biocompatible and noncytotoxic at the concentrations utilized. As future research addresses these critical challenges, injectable macroporous foams are anticipated to have an increasingly significant impact on improving patient outcomes for a number of clinical procedures.

In vitro and in vivo evaluation of biodegradable embolic microspheres with tunable anticancer drug release

Natural polymer-derived materials have attracted increasing interest in the biomedical field. Polysaccharides have obvious advantages over other polymers employed for biomedical applications due to their exceptional biocompatibility and biodegradability. None of the spherical embolic agents used clinically is biodegradable. In the current study, microspheres prepared from chitosan and carboxymethyl cellulose (CMC) were investigated as a biodegradable embolic agent for arterial embolization applications. Aside from the enzymatic degradability of chitosan units, the cross-linking bonds in the matrix, Schiff bases, are susceptible to hydrolytic cleavage in aqueous conditions, which would overcome the possible shortage of enzymes inside the arteries. The size distribution, morphology, water retention capacity and degradability of the microspheres were found to be affected by the modification degree of CMC. An anticancer drug, doxorubicin, was successfully incorporated into these microspheres for local release and thus for killing cancerous cells. These microspheres demonstrated controllable degradation time, variable swelling and tunable drug release profiles. Co-culture with human umbilical vein endothelial cells revealed non-cytotoxic nature of these microspheres compared to monolayer control (P>0.95). In addition, a preliminary study on the in vivo degradation of the microspheres (100-300μm) was performed in a rabbit renal embolization model, which demonstrated that the microspheres were compatible with microcatheters for delivery, capable of occluding the arteries, and biodegradable inside arteries. These microspheres with biodegradability would be promising for embolization therapies.

Controlled release of triamcinolone acetonide from polyurethane implantable devices: application for inhibition of inflammatory-angiogenesis

The purpose of this study was to develop triamcinolone acetonide-loaded polyurethane implants (TA PU implants) for the local treatment of different pathologies including arthritis, ocular and neuroinflammatory disorders. The TA PU implants were characterized by FTIR, SAXS and WAXS. The in vitro and in vivo release of TA from the PU implants was evaluated. The efficacy of TA PU implants in suppressing inflammatory-angiogenesis in a murine sponge model was demonstrated. FTIR results revealed no chemical interactions between polymer and drug. SAXS results indicated that the incorporation of the drug did not disturb the polymer morphology. WAXS showed that the crystalline nature of the TA was preserved after incorporation into the PU. The TA released from the PU implants efficiently inhibited the inflammatory-angiogenesis induced by sponge discs in an experimental animal model. Finally, TA PU implants could be used as local drug delivery systems because of their controlled delivery of TA.

Cell death in HeLa mediated by thermoplastic polyurethane with co-immobilized IFN-γ plus TNF-α

In order to prohibit the toxicity of free IFN-γ plus TNF-α in treating human cervical cancer HeLa cells, two kinds of thermoplastic polyurethane (polyester/polyether) biomaterials with co-immobilized IFN-γ plus TNF-α on the surfaces are prepared. The programmed cell death of HeLa induced by these biomaterials is investigated. The surface modification of these biomaterials with co-immobilized IFN-γ plus TNF-α is performed by the photo-immobilization method, and the surface structures are characterized by various techniques. The cell morphology, cell mortality, cell cycle arrest, and functional status of caspases, upon the treatment by these biomaterials, are characterized. The results show that the as-prepared biomaterials have high inhibition activity against the growth of HeLa cells. The HeLa cells mediated by the two kinds of biomaterials are mainly arrested in the G(1) phase, while those cells mediated directly by free IFN-γ plus TNF-α are mainly arrested in the S phase. It is suggested that the programmed cell death mechanism induced by these two kinds of biomaterials is both caspase-dependent and caspase-independent. Our data provide the knowledge of microscopic surface structures and cell biology basis for synthesizing the thermoplastic polyurethane biomaterials with co-immobilized IFN-γ plus TNF-α, which are promising for novel therapeutics (e.g. drug cup) design for cervical cancer patients.

Controlled drug release through a plasma polymerized tetramethylcyclo-tetrasiloxane coating barrier

A plasma polymerized tetramethylcyclo-tetrasiloxane (TMCTS) coating was deposited onto a metallic biomaterial, 316 stainless steel, to control the release rate of drugs, including daunomycin, rapamycin and NPC-15199 (N-(9-fluorenylmethoxy-carbonyl)-leucine), from the substrate surface. The plasma-state polymerized TMCTS thin film was deposited in a vacuum plasma reactor operated at a radio-frequency of 13.56 MHz, and was highly adhesive to the stainless steel, providing a smooth and hard coating layer for drugs coated on the substrate. To investigate the influence of plasma coating thickness on the drug diffusion profile, coatings were deposited at various time lengths from 20 s to 6 min, depending on the type of drug. Atomic force spectroscopy (AFM) was utilized to characterize coating thickness. Drug elution was measured using a spectrophotometer or high-performance liquid chromatography (HPLC) system. The experimental results indicate that plasma polymerized TMCTS can be used as an over-coating to control drug elution at the desired release rate. The drug-release rate was also found to be dependent on the molecular weight of the drug with plasma coating barrier on top of it. The in vitro cytotoxicity test result suggested that the TMCTS plasma coatings did not produce a cytotoxic response to mammalian cells. The non-cytotoxicity of TMCTS coating plus its high thrombo-resistance and biocompatibility are very beneficial to drug-eluting devices that contact blood.

Incorporation of ionic ligands accelerates drug release from LDI-glycerol polyurethanes

This study seeks to determine the effect of ionic ligands on the drug delivery characteristics of biodegradable polyurethane materials synthesized from lysine diisocyanate (LDI) and glycerol. Two naturally occurring, structurally related ionic species, choline chloride (CC) and isethionic acid (ISE), along with 3,3-dimethyl-butanol (DMB), their neutral carbon analog, were covalently incorporated into LDI-glycerol polyurethane materials. Selected organometallic and tertiary amine catalysts were used to fashion films and foams, respectively. The potent anticancer compound DB-67, a fluorescent camptothecin derivative, was also covalently linked to the polyurethane constructs. It was first determined that the sulfonate functional group on ISE does not react to a significant degree with isocyanate. The morphological characteristics of the polyurethane films and foams were assessed via scanning electron microscopy, showing significant differences related to the ionic ligands. The ionic materials displayed increased swelling in aqueous media over the neutral control materials. Differences in the distribution of DB-67 throughout the films and foams were then detected by fluorescence microscopy. The drug delivery characteristics of the materials were then evaluated in vitro, revealing accelerated release from ionic materials. The results of this study demonstrate the unique effects that incorporation of ionic ligands into LDI-glycerol polyurethanes have on the morphology and drug distribution of the materials. These differences have a significant impact on the drug delivery characteristics of the materials, and this information should prove useful in the design and synthesis of biodegradable controlled release systems.