Biodegradable microparticles preparation by double emulsification—Solvent extraction method: A Systematic study

Influence of Polymeric Microparticle Size and Loading Concentration on 3D Printing Accuracy and Degradation Behavior of Composite Scaffolds

Successful employment of 3D printing for delivery of therapeutic biomolecules requires protection of their bioactivity on exposure to potentially inactivating conditions. Although intermediary encapsulation of the biomolecules in polymeric particulate delivery vehicles is a promising strategy for this objective, the inclusion of such particles in 3D printing formulations may critically impact the accuracy or precision of 3D printed scaffolds relative to their intended designed architectures, as well as the degradation behavior of both the scaffolds and the included particles. The present work aimed to elucidate the effect of poly(d,l-lactic-co-glycolic acid) particle size and loading concentration on material accuracy, machine precision, and degradation of 3D printed poly(ɛ-caprolactone)-based scaffolds. Using a main effects analysis, the sizes and loading concentrations of particle delivery vehicles investigated were found to have neither a beneficial nor disadvantageous influence on the metrics of printing quality such as material accuracy and machine precision. Meanwhile, particle loading concentration was determined to influence degradation rate, whereas printing temperature affected the trends in composite weight-average molecular weight. Neither of the two particle-related parameters (concentration nor diameter) was found to exhibit a significant effect on intra-fiber nor inter-fiber porosity. These findings evidence the capacity for controlled loading of particulate delivery vehicles in 3D printed scaffolds while preserving construct accuracy and precision, and with predictable dictation of composite degradation behavior for potential controlled release of encapsulated biomolecules.

Production of nanostructured systems: Main and innovative techniques

In the constant search for the development of more-specific and more-selective drugs, especially with regard to the challenge of encapsulating hydrophilic molecules, polymer nanotechnologies are remarkable for their biocompatible and biodegradable properties. The most-used nanoencapsulation methods consist of emulsification procedures, where emulsified droplets of a given polymer and drug solidify into nanoparticles after solvent extraction from the polymeric phase. This review introduces conventional emulsification methods but also highlights new emulsification technologies such as microfluidics, membrane emulsification and other techniques, including spray drying, inkjet printing and electrospraying.

Core-Shell Type Lipidic and Polymeric Nanocapsules: the Transformative Multifaceted Delivery Systems

Amongst the several nano-drug delivery systems, lipid or polymer-based core-shell nanocapsules (NCs) have garnered much attention of researchers owing to its multidisciplinary properties and wide application. NCs are structured core-shell systems in which the core is an aqueous or oily phase protecting the encapsulated drug from environmental conditions, whereas the shell can be lipidic or polymeric. The core is stabilized by surfactant/lipids/polymers, which control the release of the drug. The presence of a plethora of biocompatible lipids and polymers with the provision of amicable surface modifications makes NCs an ideal choice for precise drug delivery. In the present article, multiple lipidic and polymeric NC (LNCs and PNCs) systems are described with an emphasis on fabrication methods and characterization techniques. Far-reaching applications as a carrier or delivery system are demonstrated for oral, parenteral, nasal, and transdermal routes of administration to enhance the bioavailability of hard-to-formulate drugs and to achieve sustained and targeted delivery. This review provide in depth understanding on core-shell NC's mechanism of absorption, surface modification, size tuning, and toxicity moderation which overshadows the drawbacks of conventional approaches. Additionally, the review shines a spotlight on the current challenges associated with core-shell NCs and applications in the foreseeable future.

Exploring Various Techniques for the Chemical and Biological Synthesis of Polymeric Nanoparticles

Nanoparticles (NPs) have remarkable properties for delivering therapeutic drugs to the body’s targeted cells. NPs have shown to be significantly more efficient as drug delivery carriers than micron-sized particles, which are quickly eliminated by the immune system. Biopolymer-based polymeric nanoparticles (PNPs) are colloidal systems composed of either natural or synthetic polymers and can be synthesized by the direct polymerization of monomers (e.g., emulsion polymerization, surfactant-free emulsion polymerization, mini-emulsion polymerization, micro-emulsion polymerization, and microbial polymerization) or by the dispersion of preformed polymers (e.g., nanoprecipitation, emulsification solvent evaporation, emulsification solvent diffusion, and salting-out). The desired characteristics of NPs and their target applications are determining factors in the choice of method used for their production. This review article aims to shed light on the different methods employed for the production of PNPs and to discuss the effect of experimental parameters on the physicochemical properties of PNPs. Thus, this review highlights specific properties of PNPs that can be tailored to be employed as drug carriers, especially in hospitals for point-of-care diagnostics for targeted therapies.

Progress in Colloid Delivery Systems for Protection and Delivery of Phenolic Bioactive Compounds: Two Study Cases—Hydroxytyrosol and Curcumin

Insufficient intake of beneficial food components into the human body is a major issue for many people. Among the strategies proposed to overcome this complication, colloid systems have been proven to offer successful solutions in many cases. The scientific community agrees that the production of colloid delivery systems is a good way to adequately protect and deliver nutritional components. In this review, we present the recent advances on bioactive phenolic compounds delivery mediated by colloid systems. As we are aware that this field is constantly evolving, we have focused our attention on the progress made in recent years in this specific field. To achieve this goal, structural and dynamic aspects of different colloid delivery systems, and the various interactions with two bioactive constituents, are presented and discussed. The choice of the appropriate delivery system for a given molecule depends on whether the drug is incorporated in an aqueous or hydrophobic environment. With this in mind, the aim of this evaluation was focused on two case studies, one representative of hydrophobic phenolic compounds and the other of hydrophilic ones. In particular, hydroxytyrosol was selected as a bioactive phenol with a hydrophilic character, while curcumin was selected as typical representative hydrophobic molecules.

PLGA/PLA-Based Long-Acting Injectable Depot Microspheres in Clinical Use: Production and Characterization Overview for Protein/Peptide Delivery

Over the past few decades, long acting injectable (LAI) depots of polylactide-co-glycolide (PLGA) or polylactic acid (PLA) based microspheres have been developed for controlled drug delivery to reduce dosing frequency and to improve the therapeutic effects. Biopharmaceuticals such as proteins and peptides are encapsulated in the microspheres to increase their bioavailability and provide a long release period (days or months) with constant drug plasma concentration. The biodegradable and biocompatible properties of PLGA/PLA polymers, including but not limited to molecular weight, end group, lactide to glycolide ratio, and minor manufacturing changes, could greatly affect the quality attributes of microsphere formulations such as release profile, size, encapsulation efficiency, and bioactivity of biopharmaceuticals. Besides, the encapsulated proteins/peptides are susceptible to harsh processing conditions associated with microsphere fabrication methods, including exposure to organic solvent, shear stress, and temperature fluctuations. The protein/peptide containing LAI microspheres in clinical use is typically prepared by double emulsion, coacervation, and spray drying techniques. The purpose of this review is to provide an overview of the formulation attributes and conventional manufacturing techniques of LAI microspheres that are currently in clinical use for protein/peptides. Furthermore, the physicochemical characteristics of the microsphere formulations are deliberated.

Continuous in-line homogenization process for scale-up production of naltrexone-loaded PLGA microparticles

Injectable, long-acting drug delivery systems provide effective drug concentrations in the blood for up to 6 months. Naltrexone-loaded poly(lactide-co-glycolide) (PLGA) microparticles were prepared using an in-line homogenization method. It allows the transition from a laboratory scale to scale-up production. This research was designed to understand how the processing parameters affect the properties of the microparticles, such as microparticle size distributions, surface and internal morphologies, drug loadings, and drug release kinetics, and thus, to control them. The in-line homogenization system was used at high flow rates for the oil- and water-phases, e.g., 100 mL/min and 400 mL/min, respectively, to continuously generate microparticles. A high molecular weight (148 kDa) PLGA at various concentrations was used to generate oil-phases with a range of viscosities and also to compare with a 64 and 79 kDa at a single, high concentration. The uniformity of the microparticles was found to be related to the viscosity of the oil-phase. As the viscosity of the oil-phase increased from 52.6 mPa∙s to 4046 mPa∙s, the span value (a measure of uniformity) increased from 1.24 to 3.1 for the microparticles generated at the homogenization speed of 2000 RPM. Increasing the PLGA concentration from 5.58% to 16.85% showed a corresponding rise in the encapsulation efficiency from 74.0% to 85.8% and drug loading (DL) from 27.4% to 31.7% for the microparticles made with the homogenization speed of 2000 RPM. These increases may be due to a faster shell formulation, enabling PLGA microparticles to entrap more naltrexone into the structure. A higher DL, however, shortened the drug release duration from 56 to 42 days. The changes in morphology of the microparticles during different phases of the in vitro release study were also studied for three types of microparticles made with different PLGA concentrations and molecular weights. As PLGA microparticles went through structural changes, the surface showed raisin-like wrinkled morphologies within the first 10 days. Then, the microparticles swelled to form smooth surfaces. The in-line approach produced PLGA microparticles with a highly reproducible size distribution, DL, and naltrexone release rate.

Sequential delivery of VEGF, FGF-2 and PDGF from the polymeric system enhance HUVECs angiogenesis in vitro and CAM angiogenesis

Angiogenesis is an organized series of events, beginning with vessel destabilization, followed by endothelial cell re-organization, and ending with vessel maturation. The formation of a mature vascular network requires precise spatial and temporal regulation of a large number of angiogenic factors, including vascular endothelial growth factor (VEGF), basic fibroblast growth factor-2 (FGF-2) and platelet-derived growth factor (PDGF). VEGF aids in vascular permeability and endothelial cell recruitment, FGF-2 activates endothelial cell proliferation and migration while PDGF stimulates vascular stability. Accordingly, VEGF may inhibit vessel stabilization while PDGF may inhibit endothelial cell recruitment. Therefore, a new polymeric system was prepared by the supercritical carbon dioxide foaming technology, which realized sequential delivery of two or more growth factors with the controlled dose and rate. Increased release of VEGF (71.10%) and FGF-2 (69.76%) compared to PDGF (43.17%) was observed for the first 7 days. Thereafter, up till 21 days, an increased rate of release of BMP-2 compared to VEGF 165 was observed. The effects of PDGF-PLAms/VEGF-FGF-2-PLGA scaffolds on angiogenesis were investigated by human umbilical vein endothelial cells (HUVECs) angiogenic differentiation in vitro and chorioallantoic membrane (CAM) angiogenesis in vivo. Sequential delivery of VEGF, FGF-2 and PDGF from structural polymer scaffolds with distinct kinetics resulted in significant angiogenic differentiation of HUVECs and rapid formation of mature vascular networks in chorioallantoic membrane. This study reported a composite scaffold with distinct release kinetics, and these results clearly indicated the importance of sequential delivery of multiple growth factors in tissue regeneration and engineering.

Designing structural features of novel benznidazole-loaded cationic nanoparticles for inducing slow drug release and improvement of biological efficacy

Several polymers have been investigated for producing cationic nanocarriers due to their ability to cross biological barriers. Polycations such as copolymers of polymethylmethacrylate are highlighted due to their biocompatibility and low toxicity. The purpose of this study was to produce small and narrow-sized cationic nanoparticles able to overcome cell membranes and improve the biological activity of benznidazole (BNZ) in normal and cancer cells. The effect of composition and procedure parameters of the used emulsification-solvent evaporation method were controlled for this purpose. The experimental approach included particle size, polydispersity index, zeta potential, atomic force microscopy (AFM), attenuated total reflectance Fourier transforms infrared spectroscopy (ATR- FTIR), drug loading efficiency, and physical stability assays. Spherical and stable (over six weeks) sub 150nm cationic nanoparticles were optimized, with the encapsulation efficiency >80%. The used drug/copolymer ratio modulated the slow drug release, which was adjusted by the parabolic diffusion mathematical model. In addition, the ability of the cationic nanoparticles improve the BNZ uptake in the normal kidney cells (HEK 293) and the human colorectal cancer cells (HT 29) demonstrate that this novel BNZ-loaded cationic has great potential as a chemotherapeutic application of benznidazole.