Controlled release of ionic drug through the positively charged temperature-responsive membranes

An overview of the transport of liquid molecules through structured polymer films, barriers and composites - Experiments correlated to structure-based simulations

Films engineered to control the transport of liquids are widely used through society. Examples include barriers in packaging, wound care products, and controlled release coatings in pharmaceutics. When observed at the macroscopic scale such films commonly appear homogeneous, however, a closer look reveals a complex nano- and microstructure that together with the chemical properties of the different domains control the transport properties. In this review we compare and discuss macroscopic transport properties, measured using the straightforward, yet highly powerful technique "modified Ussing chambers", also denoted side-by-side diffusion cells, for a wide range of structured polymer films and composites. We also discuss and compare the macroscopic observations and conclusions on materials properties with that of lattice Boltzmann simulations of transport properties based on underlying material structure and chemistry. The survey of the field: (i) highlights the use and power of modified Ussing Chambers for determining liquid transport properties of polymer films, (ii) demonstrates the predictability in both directions between macroscopic observations of transport using modified Ussing chambers and structure-based simulations, and (iii) provides experimental and theoretical insights regarding the transport-determining properties of structured polymer films and composites.

Stimuli-Regulated Smart Polymeric Systems for Gene Therapy

The physiological condition of the human body is a composite of different environments, each with its own parameters that may differ under normal, as well as diseased conditions. These environmental conditions include factors, such as pH, temperature and enzymes that are specific to a type of cell, tissue or organ or a pathological state, such as inflammation, cancer or infection. These conditions can act as specific triggers or stimuli for the efficient release of therapeutics at their destination by overcoming many physiological and biological barriers. The efficacy of conventional treatment modalities can be enhanced, side effects decreased and patient compliance improved by using stimuli-responsive material that respond to these triggers at the target site. These stimuli or triggers can be physical, chemical or biological and can be internal or external in nature. Many smart/intelligent stimuli-responsive therapeutic gene carriers have been developed that can respond to either internal stimuli, which may be normally present, overexpressed or present in decreased levels, owing to a disease, or to stimuli that are applied externally, such as magnetic fields. This review focuses on the effects of various internal stimuli, such as temperature, pH, redox potential, enzymes, osmotic activity and other biomolecules that are present in the body, on modulating gene expression by using stimuli-regulated smart polymeric carriers.

Amorphous Protic Ionic Systems as Promising Active Pharmaceutical Ingredients: The Case of the Sumatriptan Succinate Drug

In this article, we highlight the benefits coming from the application of amorphous protic ionic systems as active pharmaceutical ingredients (APIs). Using the case of the sumatriptan (STR) drug, we show that the conversion of nonionic API to partially ionized amorphous protic succinate salt (STR SUCC) brings a substantial improvement in apparent solubility. Since in general the disordered systems reveal a tendency to self-arrangement during storage, the dominant part of this article is dedicated to the physical stability issue of sumatriptan and its ionic counterpart. To recognize the crystallization tendency of the studied systems, the calorimetric measurements were performed. Additionally, the role of ion dynamics in spontaneous nucleation of amorphous sumatriptan succinate is discussed. The differential scanning calorimetry analysis of ionic and nonionic sumatriptan reveals many similarities in thermal properties of these APIs as well as distinct differences in their resistance against crystallization in the supercooled liquid state. To determine the long-term physical stability of STR SUCC at room temperature conditions, the time scale of structural relaxation below their glass transition temperatures is estimated. We show that in contrast to nonionic materials, τα predictions of STR SUCC are much more complex and require aging experiments.

Investigation of abnormal thermoresponsive PVDF membranes on casting solution, membrane morphology and filtration performance

A temperature sensitive casting solution of P(OEGMA-co-VTMOS) was prepared via an in situ polymerization method. Meanwhile, an interesting thermoresponsive PVDF membrane was obtained from the temperature sensitive casting solution.

Fabrication of a thermo-responsive membrane with cross-linked smart gates via a ‘grafting-to’ method

A novel thermo-responsive membrane with the cross-linked microspheres as smart gates is fabricated by the “grafting to” technique, which exhibits excellent thermo-responsive characteristics with satisfactory reversibility and stability.

Anion exchange membranes (AEMs) based on poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and its derivatives

Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) is considered to be a promising candidate since it enables versatile routes to obtain high performance anion exchange membranes (AEMs).

Stimuli-responsive polymers and their applications in nanomedicine

This review focuses on smart nano-materials built of stimuli-responsive (SR) polymers and will discuss their numerous applications in the biomedical field. The authors will first provide an overview of different stimuli and their corresponding, responsive polymers. By introducing myriad functionalities, SR polymers present a wide range of possibilities in the design of stimuli-responsive devices, making use of virtually all types of polymer constructs, from self-assembled structures (micelles, vesicles) to surfaces (polymer brushes, films) as described in the second section of the review. In the last section of this review the authors report on some of the most promising applications of stimuli-responsive polymers in nanomedicine. In particular, we will discuss applications pertaining to diagnosis, where SR polymers are used to construct sensors capable of selective recognition and quantification of analytes and physical variables, as well as imaging devices. We will also highlight some examples of responsive systems used for therapeutic applications, including smart drug delivery systems (micelles, vesicles, dendrimers...) and surfaces for regenerative medicine.

Hybrid Anion Exchange Hollow Fiber Membrane for Delivery of Ionic Drugs

Hybrid anion exchange hollow fiber membranes (HAEHFMs) based on bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) are proposed as potential drug carriers for four anionic model drugs, including the sodium salts of benzoate (NaBS), salicylate (NaSA), meta-amino salicylate (NaMAS), and loxoprofen (NaLS). The results of the static loading and release experiments suggest that electrostatic interaction, hydrogen bonding, and hydrophobic interaction are the main interaction patterns between the membrane and the drugs. And they are directly influenced by the external phase conditions and the drug physicochemical characteristics, such as structure, molecular weight, dissociation (pKa), and hydrogen bonding capability. Among the four different drugs, NaSA and NaMAS appear to be the most suitable for controlled release by the HAEHFM due to their excellent adsorption/release behaviors.

A review of multi-responsive membranous systems for rate-modulated drug delivery

Membrane technology is broadly applied in the medical field. The ability of membranous systems to effectively control the movement of chemical entities is pivotal to their significant potential for use in both drug delivery and surgical/medical applications. An alteration in the physical properties of a polymer in response to a change in environmental conditions is a behavior that can be utilized to prepare 'smart' drug delivery systems. Stimuli-responsive or 'smart' polymers are polymers that upon exposure to small changes in the environment undergo rapid changes in their microstructure. A stimulus, such as a change in pH or temperature, thus serves as a trigger for the release of drug from membranous drug delivery systems that are formulated from stimuli-responsive polymers. This article has sought to review the use of stimuli-responsive polymers that have found application in membranous drug delivery systems. Polymers responsive to pH and temperature have been extensively addressed in this review since they are considered the most important stimuli that may be exploited for use in drug delivery, and biomedical applications such as in tissue engineering. In addition, dual-responsive and glucose-responsive membranes have been also addressed as membranes responsive to diverse stimuli.

Poly(N-isopropylacrylamide) thin films densely grafted onto gold surface: preparation, characterization, and dynamic AFM study of temperature-induced chain conformational changes

Thermally responsive poly(N-isopropylacrylamide) (PNIPAM) films are attracting considerable attention since they offer the possibility to achieve reversible control over surface wettability and biocompatibility. In this paper, we first report a new and simple method for the grafting under melt of amine-terminated PNIPAM chains onto gold surfaces modified with a self-assembled monolayer (SAM) of reactive thiols. The formation of homogeneous tethered PNIPAM films, whose thickness can be tuned by adjusting polymer molecular weight or SAM reactivity, is evidenced by using the combination of ellipsometry, X-ray photon spectroscopy, infrared spectroscopy (PM-IRRAS), and atomic force microscopy. The calculation of grafting parameters from experimental measurements indicated the synthesis of densely grafted PNIPAM films and allowed us to predict a "brushlike" regime for the chains in good solvent. In a second part, the temperature-induced responsive properties are studied in situ by conducting dynamic AFM measurements using the amplitude modulation technique. Imaging in water environment first revealed the reversible modification of surface morphology below and above the theoretical lower critical solution temperature (LCST) of PNIPAM. Then, the determination of amplitude and phase approach curves at various temperatures provided direct measurement of the evolution of the damping factor, or similarly the dissipated energy, as a function of the probe indentation into the PNIPAM film. Most interestingly, we clearly showed the subtle and progressive thermally induced chain conformational change occurring at the scale of several nanometers around the expected LCST.