Toward chronopharmaceutical drug delivery patches and biomaterial coatings for the facilitation of wound healing

Implantation of a biomaterial entails a form of injury where the integration of the implant into the host tissue greatly depends on the proper healing of the wound. Wound healing, itself, consists of a number of physiological processes, each occurring within a characteristic time window. A composite, multilayered polymeric drug delivery carrier for adhesion to the wound site and its supply with molecules released at precise time windows at which the stages in the healing process that they target occur is conceptualized here. We also present a simplified version of one such multilayered composite fabricated by a combination of solvent casting and dip coating, comprising the base poly(ε-caprolactone) layer reinforced with hydroxyapatite nanoparticles, poly(glutamic acid) mesolayer and poly-l-lysine surface layer, each loaded with specific small molecules and released at moderately distinct timescales, partially matching the chronology of wound healing. To that end, the base layer proved suitable for the delivery of an anti-inflammatory molecule or an angiogenic agent, the mesolayer appeared appropriate for the delivery of an epithelialization promoter or a granulation factor, and the adhesive surface layer interfacing directly with the site of injury showed promise as a carrier of a vasodilator. The drug release mechanisms were diffusion-driven, suggesting that the drug/carrier interaction is a key determinant of the release kinetics, as important as the nature of the polymer and its hydrolytic degradation rate in the aqueous medium. Morphological and phase composition analyses were performed, along with the cell compatibility ones, demonstrating solid adhesion and proliferation of both transformed and primary fibroblasts on both surfaces of the composite films. The design of the multilayered composite drug delivery carriers presented here is prospective, but requires further upgrades to achieve the ideal of a perfect timing of the sequential drug release kinetics and a perfect resonance with the physiological processes defining the chronology of wound healing.

Polyelectrolyte Multi-Layered Griseofulvin Nanoparticles: Conventional versus Continuous In-Situ Layer-by-Layer Fabrication

Polyelectrolyte multilayers are promising drug carriers with potential applications in the delivery of poorly soluble drugs. Furthermore, the polyelectrolyte multilayer contributes towards electrostatic interactions, which enhances the physical and chemical stability of colloids when compared to those prepared by other approaches. The aim of this work was to generate a polyelectrolyte multilayer on well characterised nanoparticles of the poorly water-soluble drug, griseofulvin. Griseofulvin (GF) nanoparticles (300 nm) were produced by wet bead milling, bearing a negative surface charge due to the use of poly(sodium 4-styrenesulfonate) (PSS) as a stabiliser. Six further layers of alternating chitosan and PSS polyelectrolyte multilayer were successfully generated at the particle surface either via use of: (1) the conventional method of adding excess coating polymer followed by centrifugation, or (2) the continuous in situ approach of adding sufficient amount of coating polymer. The continuous in situ method was designed de novo by the consecutive addition of polymers under high shear rate mixing. In comparison to the continuous in situ method, the conventional method yielded nanoparticles of smaller size (282 ±9 nm vs. 497 ±34 nm) and higher stability by maintaining its size for 6 months. In conclusion, the parent griseofulvin nanosuspension proved to be a suitable candidate for the polyelectrolyte multilayer fabrication providing an avenue for a bespoke formulation with versatile and potentially enhanced drug delivery properties.

In situ pocket-type microcarrier (PMc) as a therapeutic composite: Regeneration of cartilage with stem cells, genes, and drugs

We prepared pocket-type micro-carriers (PMc) with pores larger than 30 μm for use in cell delivery by adding 40 mg pluronic F-127 copolymers (F-127) to biodegradable PLGA dissolved in dichloromethane solution. The controlling the size of the pockets in this way facilitates the adhesion of cells by regulating the size of the pockets according to the cells having various sizes. The size of PMc pores could be controlled within a range of 2 to 30 μm by varying the F-127 content. The ratio of F-127 to DOPA-bPEI was most appropriate at 1: 1, and the pocket size at 10 mg/ml of F-127 was appropriate for adhering 20-30 μm stem cells. F-127 containing SOX9 pDNA, in combination with DOPA-polyethylene-coated gold nanoparticles and dexamethasone loaded in PMcs, promoted cartilage differentiation. Gold nanoparticles complex and dexamethasone (DEX) loaded in PMcs were identified by micro-CT imaging and fluorescence imaging, respectively. By captured in pore generated on/in microspheres, the stem cells were safe and stable for use in delivery, both in vitro and in an animal model. Thus, microsphere pores can safely capture stem cells, and at the same time provide a microenvironment in which the captured stem cells can differentiate into chondrocytes.

pH-Sensitive Acetalated Dextran/PLGA-Based Double-Layered Microparticles and Their Application in Food Preservation

Double-layered microparticles (150-190 μm) composed of biodegradable poly(lactic-co-glycolic acid) (PLGA) and pH-responsive acetalated dextran were fabricated using a one-step emulsion solvent evaporation technique. Nearly 80% dextran was released from the microparticles after 20 days of incubation in pH ∼ 5 medium, and the complete disappearance of shell (Ac-dextran) layer was also evident from scanning electron microscopy (SEM) images after 20 days under the same condition. However, the Ac-dextran shell was found to remain unchanged in neutral pH. Dual actives such as antibacterial (benzoic acid) and antioxidant (tocopherol) were incorporated in the shell and core of the microparticles to exploit their applications as food-preserving materials. An accelerated release of antibacterial and a controlled release of antioxidant were found to be useful for prolonging the shelf life of a low-pH food such as pork broth (pH ∼ 5) over 20 days by providing complete bacterial growth inhibition and high radical scavenging efficiency (70-90%).

How does the addition of shape distinct gold nanoparticles influence on the conformational transition of poly(N-isopropylacrylamide)?

HYPOTHESIS

The subject of nanomaterials has created immense interest and expectations in the field of science and nanotechnology. Plentiful aspects proposed by gold nanoparticles (AuNPs) and their capability to affect macromolecular transition is the main driving force to execute the current study. A thermo-responsive polymer poly(N-isopropylacrylamide) (pNIPAM) is studied in presence of nanoparticles, particularly gold nanorods and nanospheres to elucidate completely the effect of their shape, surface area and structural morphology on the conformation of pNIPAM.

EXPERIMENTS

In this respect, several biophysical techniques such as fluorescence spectroscopy, dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) are utilized to examine the interaction of Au nanospheres/nanorods with pNIPAM. For a better understanding of Au nanoparticles morphology, transmission electron microscopy (TEM) is also employed.

FINDINGS

Introducing gold nanoparticles with the polymeric solution promotes the polymer to stay in the coil conformation at a higher temperature than the LCST of aqueous pNIPAM. A shift of 2 and 25.5 °C in the LCST of pNIPAM is observed along with Au nanospheres and nanorods, respectively. The current study provides a better impact in the field of biomedical science specifically drug delivery and tissue engineering as the LCST approaches human body temperature.

Layer-by-layer biofunctionalization of nanostructured porous silicon for high-sensitivity and high-selectivity label-free affinity biosensing

Nanostructured materials premise to revolutionize the label-free biosensing of analytes for clinical applications, leveraging the deeper interaction between materials and analytes with comparable size. However, when the characteristic dimension of the materials reduces to the nanoscale, the surface functionalization for the binding of bioreceptors becomes a complex issue that can affect the performance of label-free biosensors. Here we report on an effective and robust route for surface biofunctionalization of nanostructured materials based on the layer-by-layer (LbL) electrostatic nano-assembly of oppositely-charged polyelectrolytes, which are engineered with bioreceptors to enable label-free detection of target analytes. LbL biofunctionalization is demonstrated using nanostructured porous silicon (PSi) interferometers for affinity detection of streptavidin in saliva, through LbL nano-assembly of a bi-layer of positively-charged poly(allylamine hydrochloride) (PAH) and negatively-charged biotinylated poly(methacrylic acid) (b-PMAA). High sensitivity in streptavidin detection is achieved, with high selectivity and stability, down to a detection limit of 600 fM.

Prolonging food shelf-life by dual actives release from multi-layered polymer particles

Biodegradable polymer based 'controlled release packaging' technology has ability to release packaging actives in controlled manner to prolong the food shelf-life. Currently available systems are not sufficiently capable of releasing multiple actives in sustainable fashion. Hence, the purpose of this study was to develop dual actives (antioxidant and antibacterial) loaded multilayered microparticles in one step and to release them at rates suitable for long-term inhibition of bacterial growth as well as lipid oxidation in food. In order to achieve this goal, 2 kinds of multilayered polymer particles made up of PLLA (Poly(l-lactic acid)) and PLGA (Poly(dl-lactic-co-glycolic acid) with varying viscosity were developed using emulsion solvent evaporation method. Surprisingly, low viscous PLGA resulted tri-layered particles (PLGA/PLLA/PLGA: shell/middle/core) instead of bi-layered (PLGA/PLLA: shell/core) particles as observed for high viscous PLGA. The mechanism of formation of tri-layered particles was investigated in detail. The outermost layer consisted of relatively more hydrophilic polymer PLGA along with benzoic acid (antibacterial) and the inner core comprised of hydrophobic polymer PLLA and tocopherol (antioxidant). Release study demonstrated that release rate of dual actives were significantly accelerated from tri-layered particles in comparison to bi-layered one and their release profiles can be well explained with the help of Ridger-Peppas model. Both sets of particles exhibited long-term antibacterial (against both Escherichia coli and Staphylococcus aureus) as well as antioxidant effect over a period of 60 days. The results show for the first time the feasibility of using multilayered microparticles to prolong the food shelf-life by simultaneous release of multiple actives.

Rational Surface Design of Upconversion Nanoparticles with Polyethylenimine Coating for Biomedical Applications: Better Safe than Brighter?

Upconversion nanoparticles (UCNPs) coated with polyethylenimine (PEI) are popular background-free optical contrast probes and efficient drug and gene delivery agents attracting attention in science, industry, and medicine. Their unique optical properties are especially useful for subsurface nanotheranostics applications, in particular, in skin. However, high cytotoxicity of PEI limits safe use of UCNP@PEI, and this represents a major barrier for clinical translation of UCNP@PEI-based technologies. Our study aims to address this problem by exploring additional surface modifications to UCNP@PEI to create less toxic and functional nanotheranostic materials. We designed and synthesized six types of layered polymer coatings that envelop the original UCNP@PEI surface, five of which reduced the cytotoxicity to human skin keratinocytes under acute (24 h) and subacute (120 h) exposure. In parallel, we examined the photoluminescence spectra and lifetime of the surface-modified UCNP@PEI. To quantify their brightness, we developed original methodology to precisely measure the colloidal concentration to normalize the photoluminescence signal using a nondigesting mass spectrometry protocol. Our results, specified for the individual coatings, show that, despite decreasing the cytotoxicity, the external polymer coatings of UCNP@PEI quench the upconversion photoluminescence in biologically relevant aqueous environments. This trade-off between cytotoxicity and brightness for surface-coated UCNPs emphasizes the need for the combined assessment of the viability of normal cells exposed to the nanoparticles and the photophysical properties of postmodification UCNPs. We present an optimized methodology for rational surface design of UCNP@PEI in biologically relevant conditions, which is essential to facilitate the translation of such nanoparticles to the clinical applications.

Dual Intratumoral Redox/Enzyme-Responsive NO-Releasing Nanomedicine for the Specific, High-Efficacy, and Low-Toxic Cancer Therapy

Chemotherapy suffers numbers of limitations including poor drug solubility, nonspecific biodistribution, and inevitable adverse effects on normal tissues. Tumor-targeted delivery and intratumoral stimuli-responsive release of drugs by nanomedicines are considered to be highly promising in solving these problems. Compared with traditional chemotherapeutic drugs, high concentration of nitric oxide (NO) exhibits unique anticancer effects. The development of tumor-targeting and intratumoral microenvironment-responsive NO-releasing nanomedicines is highly desired. Here a novel kind of organic-inorganic composite nanomedicine (QM-NPQ@PDHNs) is presented by encapsulating a glutathione S-transferases π (GSTπ)-responsive drug O² -(2,4-dinitro-5-{[2-(β-d-galactopyranosyl olean-12-en-28-oate-3-yl)-oxy-2-oxoethyl] piperazine-1-yl} phenyl) 1-(methylethanolamino)diazen-1-ium-1,2-dilate (NPQ) as NO donor and an aggregation-induced-emission (AIE) red fluorogen QM-2 into the cores of the hybrid nanomicelles (PEGylated disulfide-doped hybrid nanocarriers (PDHNs)) with glutathione (GSH)-responsive shells. The QM-NPQ@PDHN nanomedicine is able to respond to the intratumoral over-expressed GSH and GSTπ, resulting in the responsive biodegradation of the protective organosilica shell and NPQ release, and subsequent NO release within the tumor, respectively, and thus normal organs remain unaffected. This work demonstrates a paradigm of dual intratumoral redox/enzyme-responsive NO-release nanomedicine for tumor-specific and high-efficacy cancer therapy.

Thermo-responsive polymers and their application as smart biomaterials

This review summarises smart thermo-responsive polymeric materials with reversible and ‘on–off’ remotely switchable properties for a wide range of biomedical and biomaterials applications.

Innovation in Layer-by-Layer Assembly

Methods for depositing thin films are important in generating functional materials for diverse applications in a wide variety of fields. Over the last half-century, the layer-by-layer assembly of nanoscale films has received intense and growing interest. This has been fueled by innovation in the available materials and assembly technologies, as well as the film-characterization techniques. In this Review, we explore, discuss, and detail innovation in layer-by-layer assembly in terms of past and present developments, and we highlight how these might guide future advances. A particular focus is on conventional and early developments that have only recently regained interest in the layer-by-layer assembly field. We then review unconventional assemblies and approaches that have been gaining popularity, which include inorganic/organic hybrid materials, cells and tissues, and the use of stereocomplexation, patterning, and dip-pen lithography, to name a few. A relatively recent development is the use of layer-by-layer assembly materials and techniques to assemble films in a single continuous step. We name this "quasi"-layer-by-layer assembly and discuss the impacts and innovations surrounding this approach. Finally, the application of characterization methods to monitor and evaluate layer-by-layer assembly is discussed, as innovation in this area is often overlooked but is essential for development of the field. While we intend for this Review to be easily accessible and act as a guide to researchers new to layer-by-layer assembly, we also believe it will provide insight to current researchers in the field and help guide future developments and innovation.

Core-Shell Composite Hydrogels for Controlled Nanocrystal Formation and Release of Hydrophobic Active Pharmaceutical Ingredients

Although roughly 40% of pharmaceuticals being developed are poorly water soluble, this class of drugs lacks a formulation strategy capable of producing high loads, fast dissolution kinetics, and low energy input. In this work, a novel bottom-up approach is developed for producing and formulating nanocrystals of poorly water-soluble active pharmaceutical ingredients (APIs) using core-shell composite hydrogel beads. Organic phase nanoemulsion droplets stabilized by polyvinyl alcohol (PVA) and containing a model hydrophobic API (fenofibrate) are embedded in the alginate hydrogel matrix and subsequently act as crystallization reactors. Controlled evaporation of this composite material produces core-shell structured alginate-PVA hydrogels with drug nanocrystals (500-650 nm) embedded within the core. Adjustable loading of API nanocrystals up to 83% by weight is achieved with dissolution (of 80% of the drug) occurring in as little as 30 min. A quantitative model is also developed and experimentally validated that the drug release patterns of the fenofibrate nanocrystals can be modulated by controlling the thickness of the PVA shell and drug loading. Thus, these composite materials offer a "designer" drug delivery system. Overall, our approach enables a novel means of simultaneous controlled crystallization and formulation of hydrophobic drugs that circumvents energy intensive top-down processes in traditional manufacturing.