Clonazepam release from bioerodible hydrogels based on semi-interpenetrating polymer networks composed of poly(epsilon-caprolactone) and poly(ethylene glycol) macromer

Development, Characterization, and In Vitro Evaluation of Resveratrol-Loaded Poly-(ε-caprolactone) Microcapsules Prepared by Ultrasonic Atomization for Intra-Articular Administration

: Intra-articular administration of drugs to the joint in the treatment of joint disease has the potential to minimize the systemic bioavailability and the usual side-effects associated with oral drug administration. In this work, a drug delivery system is proposed to achieve an anti-inflammatory local effect using resveratrol (RSV). This study aims to develop microcapsules made of poly-(ε-caprolactone) (PCL) by ultrasonic atomization to preserve the antioxidant activity of RSV, to prevent its degradation and to suppress the inflammatory response in activated RAW 264.7 macrophages. An experimental design was performed to build a mathematical model that could estimate the effect of nozzle power and polymer concentration on particle size and encapsulation efficiency. RSV-loaded microcapsules showed adequate morphology, particle size, and loading efficiency properties. RSV formulations exhibited negligible cytotoxicity and an efficient amelioration of inflammatory responses, in terms of Nitric Oxide (NO), ROS (Reactive Oxygen Species), and lipid peroxidation in macrophages. Thus, RSV-loaded microcapsules merit consideration as a drug delivery system suitable for intra-articular administration in inflammatory disorders affecting the joint.

Investigations on clonazepam-loaded polymeric micelle-like nanoparticles for safe drug administration during pregnancy

Medication during pregnancy is often a necessity for women to treat their acute or chronic diseases. The goal of this study is to evaluate the potential of micelle-like nanoparticles (MNP) for providing safe drug usage in pregnancy and protect both foetus and mother from medication side effects. Clonazepam-loaded MNP were prepared from copolymers [polystyrene-poly(acrylic acid) (PS-PAA), poly(ethylene glycol)-b-poly(lactic acid) (PEG-PLA) and distearyl-sn-glycero-3-phosphoethanolamine-N-[methoxy-poly(ethylene glycol) (PEG-DSPE)] with varying monomer ratios and their drug-loading efficiency, drug release ratio, particle size, surface charge and morphology were characterised. The cellular transport and cytotoxicity experiments were conducted on clonazepam and MNP formulations using placenta-choriocarcinoma-BeWo and brain-endothelial-bEnd3 cells. Clonazepam-loaded PEG₅₀₀₀-PLA₄₅₀₀ MNP reduced the drug transport through BeWo cells demonstrating that MNP may lower foetal drug exposure, thus reduce the drug side effects. However, lipofectamine modified MNP improved the transport of clonazepam and found to be promising for brain and in-utero-specific drug treatment.

Injectable phenytoin loaded polymeric microspheres for the control of temporal lobe epilepsy in rats

PURPOSE

Epilepsy is a prevalent neurological disorder with a high frequency of drug resistance. While significant advancements have been made in drug delivery systems to overcome anti-epileptic drug resistance, efficacies of materials in biological systems have been poorly studied. The purpose of the study was to evaluate the anti-epileptic effects of injectable poly(epsilon-caprolactone) (PCL) microspheres for controlled release of an anticonvulsant, phenytoin (PHT), in an animal model of epilepsy.

METHODS

PHT-PCL and Blank-PCL microspheres formulated using an oil-in-water (O/W) emulsion solvent evaporation method were evaluated for particle size, encapsulation efficiency, surface morphology and in-vitro drug release profile. Microspheres with the most suitable morphology and release characteristics weresubsequently injected into the hippocampus of a rat tetanus toxin model of temporal lobe epilepsy. Electrocorticography (ECoG)from the cerebral cortex were recorded for all animals. The number of seizure events, severity of seizures, and seizure duration were then compared between the two treatment groups.

RESULTS

We have shown that small injections of drug-loaded microspheres are biologically tolerated and released PHT can control seizures for the expected period of time that is in accord with in-vitro release data.

CONCLUSION

The study demonstrated the feasibility of polymer-based delivery systems incontrolling focal seizures.

Novel methods of antiepileptic drug delivery -- polymer-based implants

Epilepsy is a neurological disorder characterised by spontaneous seizures. Over one third of patients receive insufficient benefit from oral anti-epileptic drug (AED) therapy, and continue to experience seizures whilst on medication. Epilepsy researchers are consequently seeking new ways to deliver AEDs directly to the seizure focus in the brain in order to deliver higher, more effective doses to the seizure focus whilst bypassing the remainder of the brain and body to prevent side effects. The focus of this review will be polymer-based implants, which are polymeric devices loaded with AED that are designed for implantation at the seizure focus in order to achieve gradual, continuous release of AED direct into the region of the brain responsible for seizures. Polymer-based implants produced for epilepsy to date are based on a range of polymers, both biodegradable and non-biodegradable, and range from simple materials development studies through to investigations of implants in animal models of seizures and epilepsy, with varying degrees of success. This review describes the range of methods employed to manufacture polymer-based implants and compares their advantages and potential appeal to industry, and describes and compares the results and successes of polymer-based materials and devices produced to date for the treatment of epilepsy. We also discuss disadvantages and hurdles to be overcome in the field, and describe our predictions for advances to be made in the field in the coming decade.

Semi-interpenetrating network of polyethylene glycol and photocrosslinkable chitosan as an in-situ-forming nerve adhesive

An ideal adhesive for anastomosis of severed peripheral nerves should tolerate strains imposed on rejoined nerves. We use blends of photocrosslinkable 4-azidobenzoic acid-modified chitosan (Az-C) and polyethylene glycol (PEG) as a new in-situ-forming bioadhesive for anastomosing and stabilizing the injured nerves. Cryo-scanning electron microscopy suggests that the polymer blends form a semi-interpenetrating network (semi-IPN), where PEG interpenetrates the Az-C network and reinforces it. Az-C/PEG semi-IPN gels have higher storage moduli than Az-C gel alone and fibrin glue. Nerves anastomosed with an Az-C/PEG gel tolerate a higher force than those with fibrin glue prior to failure. A series of ex vivo and in vitro cell experiments indicate the Az-C/PEG gels are compatible with nerve tissues and cells. In addition, Az-C/PEG gels release PEG over a prolonged period, providing sustained delivery of PEG, a potential aid for nerve cell preservation through membrane fusion. Az-C/PEG semi-IPN gels are promising bioadhesives for repairing severed peripheral nerves not only because of their improved mechanical properties but also because of their therapeutic potential and tissue compatibility.

Defining and designing polymers and hydrogels for neural tissue engineering

The use of biomaterials, such as hydrogels, as neural cell delivery devices is becoming more common in areas of research such as stroke, traumatic brain injury, and spinal cord injury. When reviewing the available research there is some ambiguity in the type of materials used and results are often at odds. This review aims to provide the neuroscience community who may not be familiar with fundamental concepts of hydrogel construction, with basic information that would pertain to neural tissue applications, and to describe the use of hydrogels as cell and drug delivery devices. We will illustrate some of the many tunable properties of hydrogels and the importance of these properties in obtaining reliable and consistent results. It is our hope that this review promotes creative ideas for ways that hydrogels could be adapted and employed for the treatment of a broad range of neurological disorders.

Fabrication of supramolecular hydrogels for drug delivery and stem cell encapsulation

Supramolecular hydrogels self-assembled by alpha-cyclodextrin and methoxypolyethylene glycol-poly(caprolactone)-(dodecanedioic acid)-poly(caprolactone)-methoxypolyethylene glycol (MPEG-PCL-MPEG) triblock polymers were prepared and characterized in vitro and in vivo. The sustained release of dextran-fluorescein isothiocyanate (FITC) from the hydrogels lasted for more than 1 month, which indicated that the hydrogels were promising for controlled drug delivery. ECV304 cells and marrow mesenchymal stem cells (MSC) were encapsulated and cultured in the hydrogels, during which the morphologies of the cells could be kept. The in vitro cell viability studies and the in vivo histological studies demonstrated that the hydrogels were non-cytotoxic and biocompatible, which indicated that the hydrogels prepared were promising candidates as injectable scaffolds for tissue engineering applications.

Chronobiology, drug delivery, and chronotherapeutics

Biological processes and functions are organized in space, as a physical anatomy, and time, as a biological time structure. The latter is expressed by short-, intermediate-, and long-period oscillations, i.e., biological rhythms. The circadian (24-h) time structure has been most studied and shows great importance to the practice of medicine and pharmacotherapy of patients. The phase and amplitude of key physiological and biochemical circadian rhythms contribute to the known predictable-in-time patterns in the occurrence of serious and life-threatening medical events, like myocardial infraction and stroke, and the manifestation and severity of symptoms of chronic diseases, like allergic rhinitis, asthma, and arthritis. Moreover, body rhythms can significantly affect responses of patients to diagnostic tests and, most important to the theme of this special issue, medications. Rhythmicity in the pathophysiology of disease is one basis for chronotherapeutics--purposeful variation in time of the concentration of medicines in synchrony with biological rhythm determinants of disease activity--to optimize treatment outcomes. A second basis is the control of undesired effects of medications, especially when the therapeutic range is narrow and the potential for adverse effects high, which is the case for cancer drugs. A third basis is to meet the biological requirements for frequency-modulated drug delivery, which is the case for certain neuroendocrine peptide analogues. Great progress has been realized with hydrogels, and they offer many advantages and opportunities in the design of chronotherapeutic systems for drug delivery via the oral, buccal, nasal, subcutaneous, transdermal, rectal, and vaginal routes. Nonetheless, innovative delivery systems will be necessary to ensure optimal application of chronotherapeutic interventions. Next generation drug-delivery systems must be configurable so they (i) require minimal volitional adherence, (ii) respond to sensitive biomarkers of disease activity that often vary in time as periodic (circadian rhythmic) and non-periodic (random) patterns to release medication to targeted tissue(s) on a real time as needed basis, and (iii) are cost-effective.

Drug release from and hydrolytic degradation of a poly(ethylene glycol) grafted poly(3-hydroxyoctanoate)

Monoacrylate-poly(ethylene glycol)-grafted poly(3-hydroxyoctanoate) (PEGMA-g-PHO) copolymers were synthesized to develop a swelling-controlled release delivery system for ibuprofen as a model drug. The in vitro hydrolytic degradation of and the drug release from a film made of the PEGMA-g-PHO copolymer were carried out in a phosphate buffer saline (pH 7.4) medium. The hydrolytic degradation of the copolymer was strongly dependent on the degree of grafting (DG) of the PEGMA group. The degradation rate of the copolymer films in vitro increased with increasing DG of the PEGMA group on the PHO chain. The copolymer films showed a controlled delivery of ibuprofen to the medium in periods of time that depend on the composition, hydrophilic/hydrophobic characteristics, initial drug loading amount and film thickness of the graft copolymer support. The drug release rate from the grafted copolymer films was faster than the rate of weight loss of the films themselves. In particular, a combination of the low DG of the PEGMA group in the PHO chains with the low ibuprofen solubility in water led to long-term constant release from these matrices in vitro.

Keratinocyte-fibroblast paracrine interaction: the effects of substrate and culture condition

Interactions between epidermal-dermal cells via soluble factors provide important signals in regulating the reepithelialization of wounded skin. For example, keratinocytes regulate the expression of keratinocyte growth factor (KGF) in fibroblasts through the release of interleukin-1beta (IL-1beta). In this study, a previously developed polyethyleneglycol-based interpenetrating network (IPN) system was utilized as a platform for the delivery of keratinocyte-active factors. The effect of substrate chemistry, culture condition, and the delivery of exogenous keratinocyte-active factors on the keratinocyte behavior and the keratinocyte-fibroblast paracrine relationship was delineated. Adherent keratinocyte density on TCPS and glutaraldehyde-fixed gelatin hydrogels but not on IPN was significantly increased with culture time in the presence of growth supplements independent of the released KGF from the gelatin hydrogel and IPN. In the presence of fibroblasts, adherent keratinocyte density on gelatin hydrogels was higher than that without fibroblasts. This phenomenon was not observed on IPN and polycarbonate membrane. In summary, the delivered exogenous huKGF (i.e., released from a biomaterial matrix) operates in tandem with fibroblasts in regulating keratinocyte activation (i.e., IL-lbeta release and adhesion) in a surface-dependent manner. Immunoassay analysis of cell culture keratinocyte-fibroblast paracrine relationship as characterized by IL-1beta and KGF could not be established in the presence of IPNs, 0.1% glutaraldehyde-fixed gelatin hydrogels, and polycarbonate membranes.

Macrophage Adhesion on Gelatin-Based Interpenetrating Networks Grafted with PEGylated RGD

Human blood-derived macrophage adhesion on interpenetrating networks (IPNs) composed of PEGylated RGD-modified gelatin and poly(ethylene glycol) diacrylate was studied. The interaction between biomaterial immobilized with biofunctional peptides such as RGD and macrophages is central in the design of tissue-engineering scaffolds. PEGylated RGD-modified gelatin was synthesized via several steps involving PEG derivations and characterized by high-performance liquid chromatography, mass spectroscopy, gel permeation chromatography, and the trinitrobenzenesulfonic acid method. IPNs containing modified or unmodified gelatin were cultured with human macrophages and monitored at 2, 24, 96, and 168 h. At each time point, IPNs containing gelatin modified with PEGylated RGD showed a comparable adherent macrophage density as tissue culture polystyrene and a significantly higher cell density than other IPN formulations containing unmodified gelatin or gelatin modified with PEGylated triglycine. Although surface-immobilized RGD can serve to mediate the adhesion of different cell types on the biomaterial surface, the interaction of RGD with immune/inflammatory cells such as macrophages should also be considered when assessing the potential host response of tissue-engineering scaffolds.

Analysis of poly(ethylene glycol)-diacrylate macromer polymerization within a multicomponent semi-interpenetrating polymer network system

Semi-interpenetrating polymer networks (semi-IPNs) containing poly(ethylene glycol)-diacrylate (PEGdA) and modified gelatin were prepared with 2,2-dimethoxy-2-phenylacetophenone (DMPA) as a photoinitiator. The effect of (i) initiator and PEGdA concentration, and (ii) weight ratio and type of modified gelatin on the conversion of PEGdA functional end groups was monitored in situ using attenuated total reflectance-Fourier transform infrared (ATR-FTIR). Reaction induction time was dependent on DMPA concentration and increased with decreasing DMPA concentration. Relative reaction rate was strongly dependent on both DMPA and PEGdA concentrations. Gelatin weight ratio and modification did not significantly affect reaction induction time, relative reaction rate, or reaction end time. Swelling/degradation kinetics at various aqueous conditions sought to establish relationships between diacrylate conversion and the resulting semi-IPN physical properties. Semi-IPN swelling weight ratio was strongly dependent on solvent conditions and semi-IPN exposure to gamma-irradiation. Gelatin backbone modification and UV exposure time exhibited no effect on semi-IPN swelling weight ratio. In conclusion, ATR-FTIR presents a viable means of monitoring the conversion of PEGdA functional end groups within a complex mixture. UV exposure >10 s did not significantly affect the weight swelling ratio, and supports our ATR-FTIR results that network formation reached completion before 3 min of UV exposure.

Synthesis, characterization and drug release from three-arm poly(ε-caprolactone) maleic acid/poly(ethylene glycol) diacrylate hydrogels

A biodegradable polymer network hydrogel with both hydrophobic and hydrophilic components was synthesized and characterized. The hydrophobic and hydrophilic components were a three-arm poly(epsilon-caprolactone) maleic acid (PGCL-Ma, as the hydrophobic constituent) and poly(ethylene glycol) diacrylate macromer (PEGDA, as a hydrophilic constituent), respectively. These two polymers were chemically photo-crosslinked to generate a three-dimensional network structure, which were characterized by FT-IR, DSC and SEM. The swelling property of the networks was studied in phosphate-buffered saline (PBS, pH 7.4). The results of this study showed that a wide-range swelling property was obtained by changing the composition ratio of PGCL-Ma to PEGDA. The in vitro release of bovine serum albumin (BSA) from these hydrogels as a function of the PEGDA to PGCL-Ma composition ratio and incubation time was examined and we found that the incorporation of PEGDA into PGCL-Ma increased the initial burst release of BSA. As the PEGDA component increased, the rate of formation of a loose three-dimensional (3D) network structure increased; consequently, the sustained rate and extent of BSA release increased. We suggest that the release of BSA was controlled by both diffusion of BSA through swelling of the hydrophilic phase during an early stage and degradation of the hydrophobic phase during a late stage; and that the relative magnitude of diffusion versus degradation controlled release depended on composition ratio and immersion time.