Overview of Tissue Engineering and Drug Delivery Applications of Reactive Electrospinning and Crosslinking Techniques of Polymeric Nanofibers with Highlights on Their Biocompatibility Testing and Regulatory Aspects.

Traditional electrospinning is a promising technique for fabricating nanofibers for tissue engineering and drug delivery applications. The method is highly efficient in producing nanofibers with morphology and porosity similar to the extracellular matrix. Nonetheless, and in many instances, the process has faced several limitations, including weak mechanical strength, large diameter distributions, and scaling-up difficulties of its fabricated electrospun nanofibers. The constraints of the polymer solution's intrinsic properties are primarily responsible for these limitations. Reactive electrospinning constitutes a novel and modified electrospinning techniques developed to overcome those challenges and improve the properties of the fabricated fibers intended for various biomedical applications. This review mainly addresses reactive electrospinning techniques, a relatively new approach for making in situ or post-crosslinked nanofibers. It provides an overview of and discusses the recent literature about chemical and photoreactive electrospinning, their various techniques, their biomedical applications, and FDA regulatory aspects related to their approval and marketing. Another aspect highlighted in this review is the use of crosslinking and reactive electrospinning techniques to enhance the fabricated nanofibers' physicochemical and mechanical properties and make them more biocompatible and tailored for advanced intelligent drug delivery and tissue engineering applications.

Controlled release of bioactive IL-2 from visible light photocured biodegradable elastomers for cancer immunotherapy applications.

Biodegradable elastomeric controlled-release poly (decane-co-tricarballylate) (PDET) based matrices capable of maintaining the stability and bioactivity of Interleukin-2 (IL-2) through the utilization of visible-light curing and solvent-free loading of the cytokine are reported. The elastomeric devices were fabricated by intimately mixing lyophilized IL-2 powder with the acrylated prepolymer before photocrosslinking. The bioactivity of the released protein was assessed by its ability to stimulate the proliferation of the C57BL/6 mouse cytotoxic T lymphocyte, and its concentration was analysed using ELISA. The influence of changes in the polymer's physicochemical and mechanical properties on IL-2 release kinetics and bioactivity were also studied. The increase in the device's surface area and the incorporation of trehalose in the loaded lyophilized mix increased the IL-2 release rate with drug release proceeding via typical zero-order release kinetics. Moreover, the decrease in the degree of acrylation of the prepared devices increased the IL-2 release rate. The bioactivity assay showed that IL-2 retained over 94% of its initial bioactivity throughout 28 days of the release period. A new protein delivery vehicle composed of biodegradable PDET elastomers was demonstrated to be promising and effective for linear, constant, and sustained osmotic-driven release of bioactive IL-2 and other sensitive proteins and hormones.

Formulation of Lipid-Based Tableted Spray-Congealed Microparticles for Sustained Release of Vildagliptin: In Vitro and In Vivo Studies.

Spray-congealing (SPC) technology was utilized to prepare lipid-based microparticles (MP) capable of sustaining the release of Vildagliptin (VG) for use as a once-daily treatment for type 2 diabetes mellitus. VG microparticles were prepared using Compritol® and Gelucire®50/13 as lipid carriers in the presence of various amounts of Carbomer 934 NF. The lipid carriers were heated to 10 °C above their melting points, and VG was dispersed in the lipid melt and sprayed through the heated two-fluid nozzle of the spray congealer to prepare the VG-loaded MP (VGMP). The microparticles produced were then compressed into tablets and characterized for their morphological and physicochemical characteristics, content analysis, in vitro dissolution, and in vivo bioavailability studies in mixed-breed dogs. The VGMP were spherical with a yield of 76% of the total amount. VG was found to be in its semicrystalline form, with a drug content of 11.11% per tablet and a percentage drug recovery reaching 98.8%. The in vitro dissolution studies showed that VG was released from the tableted particles in a sustained-release fashion for up to 24 h compared with the immediate-release marketed tablets from which VG was completely released within 30 min. The in vivo pharmacokinetics studies reported a Cmax, Tmax, T1/2, and MRT of 118 ng/mL, 3.4 h, 5.27 h, and 9.8 h, respectively, for the SPC formulations, showing a significant difference (p < 0.05)) from the pk parameters of the immediate-release marketed drug (147 ng/mL, 1 h, 2.16 h, and 2.8 h, respectively). The area under the peak (AUC) of both the reference and tested formulations was comparable to indicate similar bioavailabilities. The in vitro-in vivo correlation (IVIVC) studies using multiple level C correlations showed a linear correlation between in vivo pharmacokinetics and dissolution parameters. In conclusion, SPC was successfully utilized to prepare a once-daily sustained-release VG oral drug delivery system.

Paclitaxel/methotrexate co-loaded PLGA nanoparticles in glioblastoma treatment: Formulation development and in vitro antitumor activity evaluation.

AIM: The aim of this study was to improve the therapeutic index of chemotherapeutic drugs on glioblastoma cells through an improved co-drug delivery system. MATERIALS AND METHODS: Methotrexate (MTX) and paclitaxel (PTX) were co-loaded into poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) coated with polyvinyl alcohol (PVA) and Poloxamer188 (P188). KEY FINDINGS: The mean size of the NPs was about 212 nm, with a zeta potential of about -15.7 mV. Encapsulation efficiency (EE%) and drug loading (DL%) were determined to be 72% and 4% for MTX and 85% and 4.9% for PTX, respectively. The prepared NPs were characterized by differential thermal analysis (DTA) and thermogravimetric analysis (TGA). Moreover, an in vitro sustained release profile was observed for both drug loaded PLGA NPs. Glioblastoma cellular uptake of the NPs was confirmed by fluorescence microscopy and cell survival rate was investigated through the 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method after 48 h of incubation showing IC50 values of 24.5 µg·mL-1 for PTX and 9.5 µg·mL-1 for MTX for the MTX/PTX co-loaded PLGA nanoparticles coated with PVA/P188 (Co-2 NPs). Apoptosis and necrosis were also studied via flow cytometry, the lactate dehydrogenase (LDH) assay and the amount of anti-apoptotic protein (Bcl-2) expression. Blood compatibility of the co-delivery of PTX and MTX loaded PLGA NPs was investigated using a hemolysis method as well. SIGNIFICANCE: The co-delivery of PTX and MTX loaded PLGA NPs is promising for the treatment of glioblastoma compared to their respective free drug formulations and, thus, should be further investigated.

Development, characterization and stability evaluation of ciprofloxacin-loaded parenteral nutrition nanoemulsions.

In this study, two licensed total parenteral nanoemulsion formulations (Clinoleic® and Intralipid®) were loaded with ciprofloxacin (CP). The physicochemical characteristics and stability profiles of the formulations were investigated using a range of drug concentrations. Furthermore, formulation stability was evaluated over a period of six months at room temperature (RT) or 4 °C. Loading CP into nanoemulsions resulted in no significant differences in their measured droplet size, polydispersity index (PI), zeta potential, and pH. Drug entrapment efficiency (EE) was relatively high for all formulations, regardless of nanoemulsion type, and the drug release was sustained over 24 h. Stability studies of all formulations were performed at 4 °C and RT for 180 and 60 days, respectively. At 4 °C for 180 days, both Clinoleic® and Intralipid® formulations at a range of drug concentrations (1-10 mg/ml) showed high stabilities measured periodically by the average droplet sizes, PI, pH, and zeta potential values. Similar results, but pH values, were shown when the formulations for both nanoemulsion stored at RT for 60 days. Overall, this study has shown that CP was successfully loaded into clinically licensed TPN lipid nanoemulsions. The resultant CP-loaded nanoemulsion formulations demonstrated desirable physicochemical properties and were stable upon storage at 4 °C for up to six months.

Retinal cell regeneration using tissue engineered polymeric scaffolds.

Degenerative retinal diseases, such as age-related macular degeneration (AMD), can lead to permanent sight loss. Although intravitreal anti-vascular endothelial growth factor (VEGF) and steroid injections are effective for the management of early stages of wet and/or neovascular AMD (nAMD), no proven treatments currently exist for dry AMD or for the advanced geographic atrophy of the retina that follows. Tissue engineering (TE) has recently emerged as a promising alternative to repair retinal damaged and restore its functions. Here, we review recent advances in TE, with a particular emphasis on retinal regeneration. We provide an overview of retinal diseases, followed by a comprehensive review of TE techniques, cells, and polymers used in the fabrication of scaffolds for retinal cell regenerations, in particular the retinal pigment epithelium (RPE).

Preparation and characterization of letrozole-loaded poly(d,l-lactide) nanoparticles for drug delivery in breast cancer therapy.

Letrozole (LTZ), an aromatase inhibitor used for the treatment of hormonally-positive breast cancer in postmenopausal women, has poor water solubility, rapid metabolism, and a range of side effects. In this study, polymer-based nanoparticles (NPs) incorporating the drug have been designed and characterized, aimed to control the release, potentially maximize the therapeutic efficiency, and minimize the side effects of the drug. LTZ was incorporated into poly(d,l-lactide) (PDLLA) NPs by employing the emulsion-solvent evaporation technique using a range of drug concentrations. Loaded drug and drug-polymer interactions were studied using X-ray diffraction and NPs morphology was evaluated using scanning electron microscopy (SEM). Particle size distribution (PSD) and zeta potential of the NPs were analyzed using dynamic light scattering (DLS) and laser Doppler velocimetry (LDV), respectively. Drug content and release profile studies were carried out and determined using ultra performance liquid chromatography (UPLC). The yield of LTZ-PDLLA NPs reached as high as 85%. The NPs were spherical and smooth, regardless of LTZ concentration in the formulation. However, particle size increased from 241.6 ± 1.2 to 348.7 ± 6.1 nm upon increasing LTZ concentration from 0 to 30% w/w, with entrapment efficiencies reaching up to 96.8%. Drug release from the polymeric matrix was best described by Higuchi model with a predominant diffusion-based mechanism. More than 15, 46, and 86% of LTZ was released in a controlled fashion over 30 d from the 10, 20, and 30% LTZ-PDLLA NPs, respectively. Overall, LTZ-PDLLA NPs were designed with appropriate size and surface charge, high drug loading, superior entrapment efficiency, and prolonged release profile.

Synthesis, characterization & cytocompatibility of poly (diol-co-tricarballylate) based thermally crosslinked elastomers for drug delivery & tissue engineering applications.

The aim of this study was to investigate the synthesis and in vitro characterization of thermoset biodegradable poly (diol-co-tricarballylate) (PDT) elastomeric polymers for the purpose of their use in implantable drug delivery and tissue engineering applications. The synthesis was based on thermal crosslinking technique via a polycondensation reaction of tricarballylic acid with aliphatic diols of varying chain lengths (C6-C12). PDT prepolymers were synthesized at 140 °C for 20 min. After purification, the prepolymers were molded and kept at 120 °C for 18 h under vacuum to complete the crosslinking process. PDT prepolymers were characterized by DSC, FT-IR, 1H NMR and GPC. The PDT elastomers were also subjected to thermal and structural analysis, as well as sol content, mechanical testing, in vitro degradation and cytocompatibility studies. The mechanical properties and sol content were found to be dependent on synthesis conditions and can be controlled by manipulating the crosslinking density and number of methylene groups in the chain of precursor aliphatic diol. The family of thermally crosslinked PDT biodegradable polyesters were successfully prepared and characterized; besides they have promising use in drug delivery and other biomedical tissue engineering applications.

Preparation and optimization of monodisperse polymeric microparticles using modified vibrating orifice aerosol generator for controlled delivery of letrozole in breast cancer therapy.

Letrozole (LTZ) is effective for the treatment of hormone-receptor-positive breast cancer in postmenopausal women. In this work, and for the first time, using vibrating orifice aerosol generator (VOAG) technology, monodisperse poly-ε-caprolactone (PCL), and poly (D, L-Lactide) (PDLLA) LTZ-loaded microparticles were prepared and found to elicit selective high cytotoxicity against cancerous breast cells with no apparent toxicity on healthy cells in vitro. Plackett-Burman experimental design was utilized to identify the most significant factors affecting particle size distribution to optimize the prepared particles. The generated microparticles were characterized in terms of microscopic morphology, size, zeta potential, drug entrapment efficiency, and release profile over one-month period. Long-term cytotoxicity of the microparticles was also investigated using MCF-7 human breast cancer cell lines in comparison with primary mammary epithelial cells (MEC). The prepared polymeric particles were monodispersed, spherical, and apparently smooth, regardless of the polymer used or the loaded LTZ concentration. Particle size varied from 15.6 to 91.6 µm and from 22.7 to 99.6 µm with size distribution (expressed as span values) ranging from 0.22 to 1.24 and from 0.29 to 1.48 for PCL and PDLLA based microparticles, respectively. Upon optimizing the manufacture parameters, span was reduced to 0.162-0.195. Drug entrapment reached as high as 96.8%, and drug release from PDLLA and PCL followed a biphasic zero-order release using 5 or 30% w/w drug loading in the formulations. Long-term in vitro cytotoxicity studies indicated that microparticles formulations significantly inhibited the growth of MCF-7 cell line over a prolonged period of time but did not have toxic effects on the normal breast epithelial cells.

New Three-Dimensional Poly(decanediol-co-tricarballylate) Elastomeric Fibrous Mesh Fabricated by Photoreactive Electrospinning for Cardiac Tissue Engineering Applications.

Reactive electrospinning is capable of efficiently producing in situ crosslinked scaffolds resembling the natural extracellular matrix with tunable characteristics. In this study, we aimed to synthesize, characterize, and investigate the in vitro cytocompatibility of electrospun fibers of acrylated poly(1,10-decanediol-co-tricarballylate) copolymer prepared utilizing the photoreactive electrospinning process with ultraviolet radiation for crosslinking, to be used for cardiac tissue engineering applications. Chemical, thermal, and morphological characterization confirmed the successful synthesis of the polymer used for production of the electrospun fibrous scaffolds with more than 70% porosity. Mechanical testing confirmed the elastomeric nature of the fibers required to withstand cardiac contraction and relaxation. The cell viability assay showed no significant cytotoxicity of the fibers on cultured cardiomyoblasts and the cell-scaffolds interaction study showed a significant increase in cell attachment and growth on the electrospun fibers compared to the reference. This data suggests that the newly synthesized fibrous scaffold constitutes a promising candidate for cardiac tissue engineering applications.

Fabrication & Characterization of 3D Electrospun Biodegradable Nanofibers for Wound Dressing, Drug Delivery and Other Tissue Engineering Applications.

BACKGROUND: The use of electrospinning technology (ET) in fabrication of threedimensional biodegradable electrospun nanofibers scaffolds (BENS) has recently gained considerable attention in tissue engineering. BENS are superior to other existing scaffolds in tissue regeneration as they provide high surface area-to-volume ratio, possess high porosity, and offer a biomimetic environment in a nanometer scale. OBJECTIVES: To fabricate & characterize BENS using Poly (ethylene glycol) (PEG35000) as a biodegradable polymer loaded with Amoxicillin Trihydrate (AMX) for use as a wound dressing. METHOD: Solutions of PEG35000 in chloroform of varying concentrations were used to fabricate BENS using ET. Blank & 1% w/v AMX-loaded BENS were fabricated & characterized. Morphology of BENS were assessed using Scanning Electron Microscopy (SEM). Fourier Transform Infrared (FT-IR) Spectroscopy was used to identify the interaction between PEG35000 and AMX. Differential Scanning Calorimetry (DSC) was used to assess the crystallinity and thermal behavior of the prepared BENS. The X-Ray Diffraction (XRD) analysis for the blank and drug loaded electrospun fibers was carried out to identify the changes in their crystalline pattern. The in vitro antibacterial activity against common skin Gram-negative and Gram-positive pathogens was also tested. RESULTS: Blank & AMX loaded 35% w/v PEG35000 solutions produced the most homogenous and intact nanofibers. Major bands of AMX in FTIR were clearly observed in the spectrum of AMX with PEG35000 post electrospinning. Moreover, DSC thermograms indicated that AMX existed in its amorphous dispersed state within PEG fibers supported by the disappearance of its melting peak at 190°C and confirmed by the complete absence of AMX crystals under SEM. Finally, the results of DSC were confirmed by XRD patterns. Characterizing XRD peaks of AMX loaded with PEG3500 post electrospinning disappeared as an indication of the complete dispersion of AMX in the loaded fibers and its complete conversion to the amorphous form. The in vitro antibacterial assay confirmed the efficiency of the drug loaded fibers against the common skin pathogens. CONCLUSION: BENS using PEG35000 loaded with AMX were successfully fabricated and characterized. Our findings show that PEG BENS has features that make it a promising candidate for wound healing applications.

Photo-irradiation paradigm: Mapping a remarkable facile technique used for advanced drug, gene and cell delivery.

Undoubtedly, the progression of photo-irradiation technique has provided a smart engineering tool for the state-of-the-art biomaterials that guide the biomedical and therapeutic domains for promoting the modern pharmaceutical industry. Many investigators had exploited such a potential technique to create/ameliorate numerous pharmaceutical carriers. These carriers show promising applications that vary from small drug to therapeutic protein delivery and from gene to living cell encapsulation design. Harmony between the properties of precisely engineered precursors and the formed network structure broadens the investigator's intellect for both brilliant creations and effective applications. As well, controlling photo-curing at the formulation level, through manipulating the absorption of light stimuli, photoinitiator system and photo-responsive precursor, facilitates the exploration of novel distinctive biomaterials. Discussion of utilizing different photo-curing procedures in designing/formulation of different pharmaceutical carriers is the main emphasis of this review. In addition, recent applications of these intelligent techniques in targeted, controlled, and sustained drug delivery with understanding of photo-irradiation concept and mechanism are illustrated.

Synthesis, characterization and cytocompatibility of a poly(diol-tricarballylate) visible light photo-cross-linked biodegradable elastomer.

The synthesis, characterization and in vitro cytocompatibility of a new family of photo-cross-linked amorphous poly(diol-tricarballylate) (PDT) biodegradable elastomeric polyesters are reported. The synthesis was based on the polycondensation reaction between tricarballylic acid and alkylene diols, followed by acrylation. The prepared and acrylated poly(diol-tricarballylate) (APDT) was characterized by means of FT-IR, (1)H-NMR, GPC and DSC. Liquid-to-solid photo-curing was carried out by exposing the APDT to visible light in the presence of camphorquinone as a photoinitiator. The thermal properties, mechanical characteristics, sol content, long-term in vitro degradation and cytocompatibility of the prepared PDT elastomers were also reported. The mechanical and degradation properties of this new photocurable elastomer can be precisely controlled by varying the density of acrylate moieties in the matrix of the polymer, and through changes in the pre-polymer chain length. The use of visible light cross-linking, possibility of solventless drug loading, controllable mechanical properties and cytocompatibility of these new elastomers make them excellent candidates for use in controlled implantable drug-delivery systems of protein drugs and other biomedical applications.

Osmotic-driven release of papaverine hydrochloride from novel poly(decane-co-tricarballylate) elastomeric matrices.

BACKGROUND: We have recently reported on the synthesis, characterization and biocompatibility of a novel family of visible-light photocrosslinked poly(diol-co-tricarballylate) elastomers intended for use in drug delivery and tissue engineering applications. In this work, the osmotic-driven controlled release of the water-soluble drug, papaverine hydrochloride, from poly(decane-co-tricarballylate) elastomeric cylindrical monoliths is reported. We also examined the influence of various parameters such as the degree of prepolymer acrylation, crosslinking density and the incorporation of osmotic excipients such as trehalose on the release kinetics of the drug. RESULTS: The release rate of papaverine hydrochloride was found to decrease in dissolution media of higher osmotic activity as an indication of the predominant involvement of the osmotic-driven release mechanism from the elastomeric devices. The drug release rate was also found to be dependent on the degree of macromer acrylation. Furthermore, it was found that coformulating papaverine hydrochloride with trehalose increases the release rate without altering the linear nature of the drug release kinetics. CONCLUSIONS: A new delivery vehicle composed of biodegradable poly(decane-co-tricarballylate) elastomers was demonstrated to be a promising and effective matrix for linear, constant and controllable osmotic-driven release of drugs.

Interleukin-2: evaluation of routes of administration and current delivery systems in cancer therapy.

Despite the fact that different administration routes and delivery systems have been used for interleukin-2 (IL-2) delivery, little has been reported regarding the most efficient strategies used to deliver IL-2 in a nontoxic, efficient, stable and safe manner. Systemic IL-2 administration has always been associated with rapid clearance and severe toxicity as a result of its narrow therapeutic index. Loco-regional IL-2 delivery, however, is used to localize IL-2 actions and activities into the vicinity of tumors and can result in an improved therapeutic outcome with much less side effects or toxicity. The purpose of this review is to report on the different properties and aspects of IL-2, including its mechanism of action, physicochemical properties, and structure which have an impact on the activity, stability and formulation of IL-2 dosage forms and delivery systems. In addition, advantages and limitations of the currently available techniques and strategies to deliver IL-2 will also be covered.

Sustained interferon-gamma delivery from a photocrosslinked biodegradable elastomer.

The application of protein therapeutics for long-term, localized delivery has been hindered by a lack of a delivery device that releases active protein at a concentration within their therapeutic window. A protein delivery system that uses an osmotic pressure delivery mechanism and a photocrosslinked biodegradable elastomer has been designed in an attempt to overcome this limitation. The elastomer is prepared through the UV initiated crosslinking of end terminal acrylated star-poly(epsilon-caprolactone-co-D,L-lactide). Interferon-gamma (IFN-gamma) was released from the optimum formulation at a constant rate of 23 ng/day over 21 days. A cell-based assay showed that over 83% of released IFN-gamma was bioactive. Furthermore, it was demonstrated that bovine serum albumin co-lyophilized with IFN-gamma was released at the same rate as IFN-gamma. This delivery formulation may be clinically useful for sustained, local protein drug delivery applications.

Synthesis and characterization of a photo-cross-linked biodegradable elastomer.

The synthesis and characterization of a photocurable biodegradable elastomer as a potential biomaterial for the delivery of thermosensitive drugs are described. The elastomer was prepared from UV initiated cross-linking of an acrylated star-poly(epsilon-caprolactone-co-D,L-lactide) prepolymer. The influence of the molecular weight of the acrylated prepolymer on the final elastomer mechanical and thermal properties was determined. The glass-transition temperature of the elastomers was independent of the prepolymer molecular weight and was from -6 to -8 degrees C. The Young's modulus and stress at break of the elastomers was proportional to the inverse of the prepolymer molecular weight, while the strain at break increased in a linear fashion with the prepolymer molecular weight. Over a degradation period of 12 weeks in phosphate buffered saline, the elastomers exhibited little mass loss, appreciable mechanical strength loss, and little dimensional or strain at break change.

Interferon-gamma therapy: evaluation of routes of administration and delivery systems.

Although different routes and delivery systems have been used to deliver interferon-gamma (IFN-gamma) for the treatment of a variety of viral and neoplastic diseases, little has been reported regarding the most efficient and least toxic routes and drug delivery modes required to achieve these goals. To have a greater understanding of the best strategies to use to administer this cytokine in an efficient, stable, and safe manner, this review details aspects of IFN-gamma concerning its mechanism of action, physical properties, and pharmacokinetics. One important conclusion that is drawn from this analysis is that a consistent, local concentration of IFN-gamma is necessary to achieve an optimal therapeutic response. A critical discussion covering the advantages and limitations of the currently used methodologies to deliver IFN-gamma in such a fashion is presented.