Modeling the release of curcumin from microparticles of poly(hydroxybutyrate) [PHB]

Fabrication, characterization and release behavior of α-tocopherol acetate-loaded pH-responsive polyhydroxybutyrate/cellulose acetate phthalate microbeads

Microbeads are used in personal care and cosmetic products (PCCPs) but are produced from nondegradable materials. Biodegradable polyhydroxybutyrate (PHB) has been recognized as a promising alternative material for use in PCCPs; however, utilizing PHB to encapsulate PCCPs is challenging because PCCPs need to be protected from the environment but their release needs to be permitted under specific physiological conditions. The aim of this work was to develop and evaluate pH-responsive cellulose acetate phthalate (CAP) to formulate lipophilic α-tocopherol acetate (α-TA)-loaded pH-responsive PHB/CAP microbeads. The influences of the PHB/CAP ratio and initial α-TA loading on the microbead size, surface morphology, encapsulation efficiency (%EE), loading capacity (%LC), and α-TA release profile were studied. The microbeads exhibited a spherical shape with a size of 328.7 ± 2.9 μm. The EE and LC were 86.7 ± 2.6 % and 13.5 ± 0.4 %, respectively. The release profile exhibited pH-responsive characteristics. These α-TA-loaded pH-responsive microbeads were stable with >50 % of the α-TA remaining after 90 days at 4, 25 and 45 °C in the dark. The results from the cytotoxicity assay with PSVK1 cells demonstrated that the microbeads were nontoxic. Hence, our developed formulation has the potential to be used to encapsulate oil-based drugs to formulate lipophilic substance-loaded pH-responsive microbeads.

Comparison between the Astaxanthin Release Profile of Mesoporous Bioactive Glass Nanoparticles (MBGNs) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/MBGN Composite Microspheres

In recent years, composite biomaterials have attracted attention for drug delivery applications due to the possibility of combining desired properties of their components. However, some functional characteristics, such as their drug release efficiency and likely side effects, are still unexplored. In this regard, controlled tuning of the drug release kinetic via the precise design of a composite particle system is still of high importance for many biomedical applications. This objective can be properly fulfilled through the combination of different biomaterials with unequal release rates, such as mesoporous bioactive glass nanoparticles (MBGN) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) microspheres. In this work, MBGNs and PHBV-MBGN microspheres, both loaded with Astaxanthin (ASX), were synthesised and compared in terms of ASX release kinetic, ASX entrapment efficiency, and cell viability. Moreover, the correlation of the release kinetic to phytotherapeutic efficiency and side effects was established. Interestingly, there were significant differences between the ASX release kinetic of the developed systems, and cell viability differed accordingly after 72 h. Both particle carriers effectively delivered ASX, though the composite microspheres exhibited a more prolonged release profile with sustained cytocompatibility. The release behaviour could be fine-tuned by adjusting the MBGN content in the composite particles. Comparatively, the composite particles induced a different release effect, implying their potential for sustained drug delivery applications.

A Polyhydroxyalkanoates-Based Carrier Platform of Bioactive Substances for Therapeutic Applications

Bioactive substances (BAS), such as small molecule drugs, proteins, RNA, cells, etc., play a vital role in many therapeutic applications, especially in tissue repair and regeneration. However, the therapeutic effect is still a challenge due to the uncontrollable release and instable physico-chemical properties of bioactive components. To address this, many biodegradable carrier systems of micro-nano structures have been rapidly developed based on different biocompatible polymers including polyhydroxyalkanoates (PHA), the microbial synthesized polyesters, to provide load protection and controlled-release of BAS. We herein highlight the developments of PHA-based carrier systems in recent therapeutic studies, and give an overview of its prospective applications in various disease treatments. Specifically, the biosynthesis and material properties of diverse PHA polymers, designs and fabrication of micro- and nano-structure PHA particles, as well as therapeutic studies based on PHA particles, are summarized to give a comprehensive landscape of PHA-based BAS carriers and applications thereof. Moreover, recent efforts focusing on novel-type BAS nano-carriers, the functionalized self-assembled PHA granules in vivo, was discussed in this review, proposing the underlying innovations of designs and fabrications of PHA-based BAS carriers powered by synthetic biology. This review outlines a promising and applicable BAS carrier platform of novelty based on PHA particles for different medical uses.

Fabrication and Characterization of Cinnamaldehyde-Loaded Mesoporous Bioactive Glass Nanoparticles/PHBV-Based Microspheres for Preventing Bacterial Infection and Promoting Bone Tissue Regeneration

Polyhydroxybutyrate-co-hydroxyvalerate (PHBV) is considered a suitable polymer for drug delivery systems and bone tissue engineering due to its biocompatibility and biodegradability. However, the lack of bioactivity and antibacterial activity hinders its biomedical applications. In this study, mesoporous bioactive glass nanoparticles (MBGN) were incorporated into PHBV to enhance its bioactivity, while cinnamaldehyde (CIN) was loaded in MBGN to introduce antimicrobial activity. The blank (PHBV/MBGN) and the CIN-loaded microspheres (PHBV/MBGN/CIN5, PHBV/MBGN/CIN10, and PHBV/MBGN/CIN20) were fabricated by emulsion solvent extraction/evaporation method. The average particle size and zeta potential of all samples were investigated, as well as the morphology of all samples evaluated by scanning electron microscopy. PHBV/MBGN/CIN5, PHBV/MBGN/CIN10, and PHBV/MBGN/CIN20 significantly exhibited antibacterial activity against Staphylococcus aureus and Escherichia coli in the first 3 h, while CIN releasing behavior was observed up to 7 d. Human osteosarcoma cell (MG-63) proliferation and attachment were noticed after 24 h cell culture, demonstrating no adverse effects due to the presence of microspheres. Additionally, the rapid formation of hydroxyapatite on the composite microspheres after immersion in simulated body fluid (SBF) during 7 d revealed the bioactivity of the composite microspheres. Our findings indicate that this system represents an alternative model for an antibacterial biomaterial for potential applications in bone tissue engineering.

Integration of Mesoporous Bioactive Glass Nanoparticles and Curcumin into PHBV Microspheres as Biocompatible Composite for Drug Delivery Applications

Bioactive glasses (BGs) are being increasingly considered for biomedical applications. One convenient approach to utilize BGs in tissue engineering and drug delivery involves their combination with organic biomaterials in order to form composites with enhanced biocompatibility and biodegradability. In this work, mesoporous bioactive glass nanoparticles (MBGN) have been merged with polyhydroxyalkanoate microspheres with the purpose to develop drug carriers. The composite carriers (microspheres) were loaded with curcumin as a model drug. The toxicity and delivery rate of composite microspheres were tested in vitro, reaching a curcumin loading efficiency of over 90% and an improving of biocompatibility of different concentrations of MBGN due to its administrations through the composite. The composite microspheres were tested in terms of controlled release, biocompatibility and bioactivity. Our results demonstrate that the composite microspheres can be potentially used in biomedicine due to their dual effects: bioactivity (due to the presence of MBGN) and curcumin release capability.

Recent advances in the production of biomedical systems based on polyhydroxyalkanoates and exopolysaccharides

In recent years, growing attention has been devoted to naturally occurring biological macromolecules and their ensuing application in agriculture, cosmetics, food and pharmaceutical industries. They inherently have antigenicity, low immunogenicity, excellent biocompatibility and cytocompatibility, which are ideal properties for the design of biomedical devices, especially for the controlled delivery of active ingredients in the most diverse contexts. Furthermore, these properties can be modulated by chemical modification via the incorporation of other (macro)molecules in a random or controlled way, aiming at improving their functionality for each specific application. Among the wide variety of natural polymers, microbial polyhydroxyalkanoates (PHAs) and exopolysaccharides (EPS) are often considered for the development of original biomaterials due to their unique physicochemical and biological features. Here, we aim to fullfil a gap on the present associated literature, bringing an up-to-date overview of ongoing research strategies that make use of PHAs (poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-co-3-hydroxyvalerate), poly (3-hydroxyoctanoate), poly(3-hydroxypropionate), poly (3-hydroxyhexanoate-co-3-hydroxyoctanoate), and poly (3-hydroxybutyrate-co-3-hydroxyhexanoate)) and EPS (bacterial cellulose, alginates, curdlan, pullulan, xanthan gum, dextran, hyaluronan, and schizophyllan) as sources of interesting and versatile biomaterials. For the first time, a monograph addressing the properties, pros and cons, status, challenges, and recent progresses regarding the application of these two important classes of biopolymers in biomedicine is presented.

Degradation Behavior of Polymers Used as Coating Materials for Drug Delivery-A Basic Review

The purpose of the work was to emphasize the main differences and similarities in the degradation mechanisms in the case of polymeric coatings compared with the bulk ones. Combined with the current background, this work reviews the properties of commonly utilized degradable polymers in drug delivery, the factors affecting degradation mechanism, testing methods while offering a retrospective on the evolution of the controlled release of biodegradable polymeric coatings. A literature survey on stability and degradation of different polymeric coatings, which were thoroughly evaluated by different techniques, e.g., polymer mass loss measurements, surface, structural and chemical analysis, was completed. Moreover, we analyzed some shortcomings of the degradation behavior of biopolymers in form of coatings and briefly proposed some solving directions to the main existing problems (e.g., improving measuring techniques resolution, elucidation of complete mathematical analysis of the different degradation mechanisms). Deep studies are still necessary on the dynamic changes which occur to biodegradable polymeric coatings which can help to envisage the future performance of synthesized films designed to be used as medical devices with application in drug delivery.

Evaluation of the Hemocompatibility and Anticancer Potential of Poly(ε-Caprolactone) and Poly(3-Hydroxybutyrate) Microcarriers with Encapsulated Chrysin

In this work, novel chrysin-loaded poly(ε-caprolactone) and poly(3-hydroxybutyrate) microcarriers were synthesized according to a modified oil-in-water single emulsion/solvent evaporation method, utilizing poly(vinyl alcohol) surfactant as stabilizer and dispersing agent for the emulsification, and were evaluated for their physico-chemical and morphological properties, loading capacity and entrapment efficiency and in vitro release of their load. The findings suggest that the novel micro-formulations possess a spherical and relatively wrinkled structure with sizes ranging between 2.4 and 24.7 µm and a highly negative surface charge with z-potential values between (-18.1)-(-14.1) mV. The entrapment efficiency of chrysin in the poly(ε-caprolactone) and poly(3-hydroxybutyrate) microcarriers was estimated to be 58.10% and 43.63%, whereas the loading capacity was found to be 3.79% and 15.85%, respectively. The average release percentage of chrysin was estimated to be 23.10% and 18.01%, respectively. The novel micromaterials were further biologically evaluated for their hemolytic activity through hemocompatibility studies over a range of hematological parameters and cytoxicity against the epithelial human breast cancer cell line MDA-MB 231. The poly(ε-caprolactone) and poly(3-hydroxybutyrate) microcarriers reached an IC50 value with an encapsulated chrysin content of 149.19 µM and 312.18 µM, respectively, and showed sufficient blood compatibility displaying significantly low (up to 2%) hemolytic percentages at concentrations between 5 and 500 µg·mL-1.

Modeling the release of food bioactive ingredients from carriers/nanocarriers by the empirical, semiempirical, and mechanistic models

The encapsulation process has been utilized in the field of food technology to enhance the technofunctional properties of food products and the delivery of nutraceutical ingredients via food into the human body. The latter application is very similar to drug delivery systems. The inherent sophisticated nature of release mechanisms requires the utilization of mathematical equations and statistics to predict the release behavior during the time. The science of mathematical modeling of controlled release has gained a tremendous advancement in drug delivery in recent years. Many of these modeling methods could be transferred to food. In order to develop and design enhanced food controlled/targeted bioactive release systems, understanding of the underlying physiological and chemical processes, mechanisms, and principles of release and applying the knowledge gained in the pharmaceutical field to food products is a big challenge. Ideally, by using an appropriate mathematical model, the formulation parameters could be predicted to achieve a specific release behavior. So, designing new products could be optimized. Many papers are dealing with encapsulation approaches and evaluation of the impact of process and the utilized system on release characteristics of encapsulated food bioactives, but still, there is no deep insight into the mathematical release modeling of encapsulated food materials. In this study, information gained from the pharmaceutical field is collected and discussed to investigate the probable application in the food industry.