Use of degradable and nondegradable nanomaterials for controlled release

Nanocomposite scaffolds for accelerating chronic wound healing by enhancing angiogenesis

Skin is the body's first barrier against external pathogens that maintains the homeostasis of the body. Any serious damage to the skin could have an impact on human health and quality of life. Tissue engineering aims to improve the quality of damaged tissue regeneration. One of the most effective treatments for skin tissue regeneration is to improve angiogenesis during the healing period. Over the last decade, there has been an impressive growth of new potential applications for nanobiomaterials in tissue engineering. Various approaches have been developed to improve the rate and quality of the healing process using angiogenic nanomaterials. In this review, we focused on molecular mechanisms and key factors in angiogenesis, the role of nanobiomaterials in angiogenesis, and scaffold-based tissue engineering approaches for accelerated wound healing based on improved angiogenesis.

Electrostimulated Release of Neutral Drugs from Polythiophene Nanoparticles: Smart Regulation of Drug-Polymer Interactions

Poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles are loaded with curcumin and piperine by in situ emulsion polymerization using dodecyl benzene sulfonic acid both as a stabilizer and a doping agent. The loaded drugs affect the morphology, size, and colloidal stability of the nanoparticles. Furthermore, kinetics studies of nonstimulated drug release have evidenced that polymer···drug interactions are stronger for curcumin than for piperine. This observation suggests that drug delivery systems based on combination of the former drug with PEDOT are much appropriated to show an externally tailored release profile. This is demonstrated by comparing the release profiles obtained in presence and absence of electrical stimulus. Results indicate that controlled and time-programmed release of curcumin is achieved in a physiological medium by applying a negative voltage of -1.25 V to loaded PEDOT nanoparticles.

Composite CD-MOF nanocrystals-containing microspheres for sustained drug delivery

Metal-organic frameworks (MOFs), which are typically embedded in polymer matrices as composites, are emerging as a new class of carriers for sustained drug delivery. Most of the MOFs and the polymers used so far in these composites, however, are not pharmaceutically acceptable. In the investigation reported herein, composites of γ-cyclodextrin (γ-CD)-based MOFs (CD-MOFs) and polyacrylic acid (PAA) were prepared by a solid in oil-in-oil (s/o/o) emulsifying solvent evaporation method. A modified hydrothermal protocol has been established which produces efficiently at 50 °C in 6 h micron (5-10 μm) and nanometer (500-700 nm) diameter CD-MOF particles of uniform size with smooth surfaces and powder X-ray diffraction patterns that are identical with those reported in the literature. Ibuprofen (IBU) and Lansoprazole (LPZ), both insoluble in water and lacking in stability, were entrapped with high drug loading in nanometer-sized CD-MOFs by co-crystallisation (that is more effective than impregnation) without causing MOF crystal degradation during the loading process. On account of the good dispersion of drug-loaded CD-MOF nanocrystals inside polyacrylic acid (PAA) matrices and the homogeneous distribution of the drug molecules within these crystals, the composite microspheres exhibit not only spherical shapes and sustained drug release over a prolonged period of time, but they also demonstrate reduced cell toxicity. The cumulative release rate for IBU (and LPZ) follows the trend: IBU-γ-CD complex microspheres (ca. 80% in 2 h) > IBU microspheres > IBU-CD-MOF/PAA composite microspheres (ca. 50% in 24 h). Importantly, no burst release of IBU (and LPZ) was observed from the CD-MOF/PAA composite microspheres, suggesting an even distribution of the drug as well as strong drug carrier interactions inside the CD-MOF. In summary, these composite microspheres, composed of CD-MOF nanocrystals embedded in a biocompatible polymer (PAA) matrix, constitute an efficient and pharmaceutically acceptable MOF-based carrier for sustained drug release.

Buffer-stable chitosan-polyglutamic acid hybrid nanoparticles for biomedical applications

In spite of their attractive features, widespread biomedical applications of CS nanoparticles are yet to be realized due to their poor stability in physiological conditions, such as in buffer system at pH 7.4. Buffer-stable chitosan-based hybrid NPs (HNPs) are reported and characterized. Buffer stability is achieved by introducing polyglutamic acid to chitosan. The effect of PGA to CS molar ratio and crosslinking on HNP integrity, buffer stability, and biodegradability are studied. Preliminary in vitro studies are carried out to evaluate targeted uptake efficiency of folate conjugated HNPs. Successful demonstration of buffer stability and cancer cell targeting by HNPs achieves important milestones for chitosan-based nanoparticle technology.

Nanowired drug delivery for neuroprotection in central nervous system injuries: modulation by environmental temperature, intoxication of nanoparticles, and comorbidity factors

Recent developments in nanomedicine resulted in targeted drug delivery of active compounds into the central nervous system (CNS) either through encapsulated material or attached to nanowires. Nanodrug delivery by any means is supposed to enhance neuroprotection due to rapid accumulation of drugs within the target area and a slow metabolism of the compound. These two factors enhance neuroprotection than the conventions drug delivery. However, this is still uncertain whether nanodrug delivery could alter the pharmacokinetics of compounds making it more effective or just longer exposure of the compound for extended period of time is primarily responsible for enhanced effects of the drugs. Our laboratory is engaged in understanding of the nanodrug delivery using TiO(2) nanowires in CNS injuries models, for example, spinal cord injury (SCI), hyperthermia and/or intoxication of nanoparticles with or without other comorbidity factors, that is, diabetes or hypertension in rat models. Our observations suggest that nanowired drug delivery is effective under normal situation of SCI and hyperthermia as evidenced by significant reduction in the blood-brain barrier (BBB) breakdown, brain edema formation, cognitive disturbances, neuronal damages, and brain pathologies. However, when the pathophysiology of these CNS injuries is aggravated by nanoparticles intoxication or comorbidity factors, adjustment in dosage of nanodrug delivery is needed. This indicates that further research in nanomedicine is needed to explore suitable strategies in achieving greater neuroprotection in CNS injury in combination with nanoparticles intoxication or other comorbidity factors for better clinical practices.

Nanodetoxification: emerging role of nanomaterials in drug intoxication treatment

Treatment for intoxication involves the neutralization or clearance of a toxic compound, but the current methods of treatment are limited in their ability to safely and effectively detoxify the patient. Emerging research has focused on using nanoparticles as parenteral detoxifying agents to circulate through the body and capture toxins. The variable compositions of these nanoparticles control the mechanism in which they capture and remove specific compounds. As discussed in this article, the recent methods for utilizing nanoparticles for detoxification show great potential for intoxication treatment. However, several challenges must be overcome before a universal nanoparticle detoxification method is available for clinical use.

Nano-organized shells and their application in controlled release

Aim: The release characteristics of hollow-shell drug-delivery carriers are strongly dependent on the properties of the capsule shell, in particular its thickness and porous structure. The aim of this investigation was to conduct a detailed study of the relationship between capsule processing parameters, the resulting shell characteristics and subsequent release of an encapsulated liquid. Methods: Hollow spherical polymer capsules of constant outer diameter were prepared using electrohydrodynamic processing and the shell thickness of the capsules varied between 100–150 nm. For each type of capsule, the size and structure of channels present in the shell were extensively studied using electron microscopy. To investigate the effect upon the release characteristics the capsules were loaded with a water-soluble dye of molecular weight approximately 961 and release profiles determined using ultraviolet spectroscopy. Results: The channel diameter was found to be similar for all shell thicknesses (˜5 nm). The majority of the channels were radially aligned and through the full thickness of the shell. It was found that the rate of release decreased with increasing shell thickness and it became increasingly linear with respect to time; modeling confirmed that the release was diffusion dominated. Conclusions: The results of the study show that by controlling the structural characteristics of the shell of the hollow drug-carrier particles at the nanoscale through their forming methodology, the release profile can in turn be tailored according to the application requirements.

Superparamagnetic nanosystems based on iron oxide nanoparticles for biomedical imaging

Magnetic iron oxide nanoparticles and their dispersion in various mediums are of wide interest for their biomedical applications and physicochemical properties. MFe2O4 or MOFe2O3 (where M = Co, Li, Ni or Mn, for example) can be molecularly engineered to provide a wide range of magnetic properties. In this article, we survey the literature, integrating the results of our work to give a rational view on the synthesis, physicochemical properties and applications of MFe2O4, especially for MRI. However, retrieving detailed biological information on a subcellular level is difficult, owing to the limited resolution and low sensitivity of the MRI technique. Thus, this article also concentrates on the development of a magnetic iron oxide nanoparticles/quantum dot hybrids, as a dual-mode magnetic-fluorescent probe. The synthesis and physicochemical properties of the magnetic iron oxide nanoparticles/quantum dot hybrids and, especially, its application as an MRI-fluorescent probe, will also be described.

Optically guided controlled release from liposomes with tunable plasmonic nanobubbles

A new method of optically guided controlled release was experimentally evaluated with liposomes containing a molecular load and gold nanoparticles (NPs). NPs were exposed to short laser pulses to induce transient vapor bubbles around the NPs, plasmonic nanobubbles, in order to disrupt the liposome and eject its molecular contents. The release efficacy was tuned by varying the lifetime and size of the nanobubble with the fluence of the laser pulse. Optical scattering by nanobubbles correlated to the molecular release and was used to guide the release. The release of two fluorescent proteins from individual liposomes has been directly monitored by fluorescence microscopy, while the generation of the plasmonic nanobubbles was imaged and measured with optical scattering techniques. Plasmonic nanobubble-induced release was found to be a mechanical, nonthermal process that requires a single laser pulse and ejects the liposome contents within a millisecond timescale without damage to the molecular cargo and that can be controlled through the fluence of laser pulse.

A survey of bioengineering research in Canada-2007

Research activity in bioengineering at Canadian universities has been surveyed. Details were provided by chemical engineering departments in response to a common request for information on activities by individual researchers and for key publications. The information provided has been grouped by topics within the broad theme of "Bioengineering," and contributions from individual departments have been summarized within these topics. Although many aspects of bioengineering research are being pursued in Canada, it would appear as though environmental biotechnology, biomaterials, and tissue/cell culture are the most active areas under investigation.

Neural interfaces at the nanoscale

Bioelectrical neural interfaces provide a means of recording the activity from the nervous system and delivering therapeutic stimulation to restore neurological function lost during disease or injury. Although neural interfaces have reached clinical utility, reducing the size of the bioelectrical interface to minimize damage to neural tissue and maximize selectivity has proven problematic. Nanotechnology may offer a means of interfacing with the nervous system with unprecedented specificity. Emergent applications of nanotechnology to neuroscience include molecular imaging, drug delivery across the BBB, scaffolds for neural regeneration and bioelectrical interfaces. In particular, carbon nanotubes offer the promises of material stability and low electrical impedance at physical dimensions that could have a significant impact on the future on neural interfaces. The purpose of this review is to present recent advances in carbon nanotube-based bioelectrical interfaces for the nervous system and discuss research challenges and opportunities.

Estimation of drug-polymer miscibility and solubility in amorphous solid dispersions using experimentally determined interaction parameters

PURPOSE

The amorphous form of a drug may provide enhanced solubility, dissolution rate, and bioavailability but will also potentially crystallize over time. Miscible polymeric additives provide a means to increase physical stability. Understanding the miscibility of drug-polymer systems is of interest to optimize the formulation of such systems. The purpose of this work was to develop experimental models which allow for more quantitative estimates of the thermodynamics of mixing amorphous drugs with glassy polymers.

MATERIALS AND METHODS

The thermodynamics of mixing several amorphous drugs with amorphous polymers was estimated by coupling solution theory with experimental data. The entropy of mixing was estimated using Flory-Huggins lattice theory. The enthalpy of mixing and any deviations from the entropy as predicted by Flory-Huggins lattice theory were estimated using two separate experimental techniques; (1) melting point depression of the crystalline drug in the presence of the amorphous polymer was measured using differential scanning calorimetry and (2) determination of the solubility of the drug in 1-ethyl-2-pyrrolidone. The estimated activity coefficient was used to calculate the free energy of mixing of the drugs in the polymers and the corresponding solubility.

RESULTS

Mixtures previously reported as miscible showed various degrees of melting point depression while systems reported as immiscible or partially miscible showed little or no melting point depression. The solubility of several compounds in 1-ethyl-2-pyrrolidone predicts that most drugs have a rather low solubility in poly(vinylpyrrolidone).

CONCLUSIONS

Miscibility of various drugs with polymers can be explored by coupling solution theories with experimental data. These approximations provide insight into the physical stability of drug-polymer mixtures and the thermodynamic driving force for crystallization.