Effects of the type of release medium on drug release from PLGA-based microparticles: Experiment and theory

PLGA-based long-acting injectable (LAI) formulations

Long-acting injectable (LAI) formulations, which deliver drugs over weeks or months, have been in use for more than three decades. Most clinically approved LAI products are formulated using poly(lactide-co-glycolide) (PLGA) polymers. Historically, the development of PLGA-based LAI formulations has relied predominantly on trial-and-error methods, primarily due to a limited understanding of the complex factors involved in LAI formulations and insufficient analytical techniques available for characterizing individual PLGA polymers of the prepared formulations. This article offers a personal perspective on recent advancements in characterization methods for PLGA polymers within final formulations, i.e., products, as well as enhanced insights into the drug release mechanisms associated with LAI products. With a deeper understanding of PLGA polymer properties and drug release mechanisms, the formulation development process can transition from traditional trial-and-error practices to a more systematic Quality by Design (QbD) approach. Additionally, this article explores the emerging role of artificial intelligence (AI) in formulation science and its potential, when applied carefully, to enhance the future development of PLGA-based LAI formulations.

In vitro-in vivo correlation (IVIVC) development for long-acting injectable drug products based on poly(lactide-co-glycolide)

In vitro-in vivo correlation (IVIVC), linking in vitro drug release to in vivo drug release or in vivo drug absorption, has been explored chiefly for oral extended-release dosage forms. Currently, there are no official guidelines on IVIVC development for non-oral drug delivery systems. Recently, many long-acting injectable (LAI) formulations based on poly(lactide-co-glycolide) (PLGA) have been developed to deliver various drugs, ranging from small molecules to peptides and proteins, for up to 6 months. The circumstances involved in the LAI formulations are drastically different from those in oral formulations, which generally deliver drugs for a maximum of 24 h. This article examines 37 IVIVC studies of PLGA microparticle formulations available in the literature. Understanding and establishing an IVIVC of LAI formulations requires more than merely plotting the percentage in vitro drug release against the percentage in vivo absorption. In vivo drug absorption (or release) should be measured to provide a complete pharmacokinetic profile when feasible. Accelerated in vitro release methods need to be respective of the real-time measurements by sharing the same release mechanism. Obtaining meaningful IVIVCs with predictive capability will be highly useful for future regulatory actions and for developing generic and new formulations.

Polymeric nanoparticles produced by electrohydrodynamic atomisation for the passive delivery of imatinib

Imatinib is a chemotherapeutic agent known to cause severe side effects when administrated systemically. Encapsulating imatinib in co-polymer poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) offers a targeted drug delivery. In this work, PLGA 50:50 and PLGA 75:25 NPs encapsulated imatinib using the electrohydrodynamic atomisation technique. All particles generated were spherical with a smooth surface with a size distribution of 455±115 nm (PLGA 50:50) and 363±147 nm (PLGA 75:25). Encapsulation of imatinib was shown to be higher than 75 % and was shown to increase the zeta potential of the loaded NPs. The release of imatinib showed an initial burst in the first 12 h, followed by different sustained releases with up to 70 %. Both types of imatinib-loaded NPs' effect on cell viability and their cellular uptake were also studied on A549 cells, and the antiproliferative effect was comparable to that of cells treated with free drugs. Finally, Rhodamine-B-loaded NP-treated cells demonstrated the cellular uptake of NPs.

Design and synthesis of drug hydrogels containing carboxymethylcellulose with honeycomb structure and pH-sensitivity as drug delivery systems for adriamycin, metformin, and naproxen

The aim of this research is to prepare and identify functionalized carboxymethylcellulose/mesoporous silica nanohydrogels (CMC/NH2-MCM-41) for obtaining a pH-sensitive system for the controlled release of drugs. The beads of CMC/NH2-MCM-41 nanocomposites were prepared by dispersing NH2-MCM-41 in a CMC polymer matrix and crosslinking with ferric ions (Fe3+). The SEM analysis of samples revealed enhancement in surface porosity of the functionalized nanohydrogel beads compared to the conventional beads. Swelling of the prepared functionalized nanohydrogels was evaluated at various pH values including pH = 7.35-7.45 (simulated body fluid or healthy cells), pH = 6 (simulated intestinal fluid), and pH = 1.5-3.5 (simulated gastric fluid). The swelling of CMC/MCM-41 and CMC/NH2-MCM-41 nanohydrogels at the pH values of simulated body fluid and simulated intestinal fluid is much higher than that of simulated gastric fluid, indicating successful synthesis of pH-sensitive nanohydrogels for drug delivery. The drug loading results showed that drug release in the CMC/NH2-MCM-41 system is much slower than that in the CMC/MCM-41 system. The results of the survival studies for the manufactured systems showed a very good biocompatibility of the designed drug delivery systems for biological applications. By coating the surface of functionalized mesopores with CMC hydrogel, we were able to develop a pH-sensitive intelligent drug delivery system.

Revisiting the in-vitro and in-vivo considerations for in-silico modelling of complex injectable drug products

Complex injectable drug products (CIDPs) have often been developed to modulate the pharmacokinetics along with efficacy for therapeutic agents used for remediation of chronic disorders. The effective development of CIDPs has exhibited complex kinetics associated with multiphasic drug release from the prepared formulations. Consequently, predictability of pharmacokinetic modelling for such CIDPs has been difficult and there is need for advanced complex computational models for the establishment of accurate prediction models for in-vitro-in-vivo correlation (IVIVC). The computational modelling aims at supplementing the existing knowledge with mathematical equations to develop formulation strategies for generation of predictable and discriminatory IVIVC. Such an approach would help in reduction of the burden of effect of hidden factors on preclinical to clinical translations. Computational tools like physiologically based pharmacokinetics (PBPK) modelling have combined physicochemical and physiological properties along with IVIVC characteristics of clinically used formulations. Such techniques have helped in prediction and understanding of variability in pharmacodynamic parameters of potential generic products to clinically used formulations like Doxil®, Ambisome®, Abraxane® in healthy and diseased population using mathematical equations. The current review highlights the important formulation characteristics, in-vitro, preclinical in-vivo aspects which need to be considered while developing a stimulatory predictive PBPK model in establishment of an IVIVC and in-vitro-in-vivo relationship (IVIVR).

Calcium phosphate bone cements as local drug delivery systems for bone cancer treatment

Bone cancer is usually a metastatic disease, affecting people of all ages. Its effective therapy requires a targeted drug administration locally at the cancer site so that the surrounding healthy organs and tissues stay unharmed. Upon a thorough literature search, a tremendous number of published articles are reporting on development of calcium phosphate cements (CPCs) for the treatment of a variety of diseases, such as osteoporosis, osteoarthritis, osteomyelitis, and other musculoskeletal disorders. However, just a limited number of research employs CPCs specifically for bone cancer treatment. In this review article, we study the factors influencing the local drug release from CPCs and particularly focus on bone cancer therapy. Finally, we locate the deficiencies in the literature regarding this specific topic and propose which other perspectives should be considered and discussed in future articles.

How bulk fluid renewal can affect in vitro drug release from PLGA implants: Importance of the experimental set-up

The aim of this study was to better understand the potential impact of partial vs. complete renewal of the bulk fluid during drug release measurements from poly (lactic-co-glycolic acid) (PLGA)-based implants. A “standard experimental set-up”, in which the implants were directly exposed to well agitated phosphate buffer pH 7.4 was used, as well as set-ups, in which the implants were embedded within agarose hydrogels (mimicking living tissue). The gels were exposed to well agitated phosphate buffer pH 7.4. Ibuprofen-loaded implants were prepared by hot melt extrusion. The systems were thoroughly characterized before and during drug release by optical and scanning electron microscopy, gravimetric analysis, pH and solubility measurements as well as gel permeation chromatography. The bulk fluid was either completely or partially replaced by fresh medium at each sampling time point. In all cases, sink conditions were provided in the agitated bulk fluids throughout the experiments. Interestingly, the agarose set-ups did not show any noteworthy impact of the bulk fluid sampling volume on the observed drug release patterns, whereas complete fluid renewal in the “standard set-up” led to accelerated drug release. This could be explained by the considerable fragility of the implants once substantial polymer swelling set on, transforming them into PLGA gels: Complete fluid renewal caused partial disintegration and damage of the highly swollen systems, decreasing the lengths of the diffusion pathways for the drug. The mechanical stress is very much reduced at low sampling volumes, or if the implants are embedded within agarose gels. Thus, great care must be taken when defining the conditions for in vitro drug release measurements from PLGA-based implants: Once substantial system swelling sets on, the devices become highly fragile.

Surface analysis of sequential semi-solvent vapor impact (SAVI) for studying microstructural arrangements of poly(lactide-co-glycolide) microparticles

Biodegradable poly(lactide-co-glycolide) (PLGA) microparticles have been used as long-acting injectable (LAI) drug delivery systems for more than three decades. Despite extensive use, few tools have been available to examine and compare the three-dimensional (3D) structures of microparticles prepared using different compositions and processing parameters, all collectively affecting drug release kinetics. Surface analysis after sequential semi-solvent impact (SASSI) was conducted by exposing PLGA microparticles to different semi-solvent in the liquid phase. The use of semi-solvent liquids presented practical experimental difficulties, particularly in observing the same microparticles before and after exposure to semi-solvents. The difficulties were overcome by using a new sequential semi-solvent vapor (SSV) method to examine the morphological changes of the same microparticles. The SASSI method based on SSV is called surface analysis of semi-solvent vapor impact (SAVI). Semi-solvents are the solvents that dissolve PLGA polymers depending on the polymer's lactide:glycolide (L:G) ratio. A sequence of semi-solvents was used to dissolve portions of PLGA microparticles in an L:G ratio-dependent manner, thus revealing different structures depending on how microparticles were prepared. Exposing PLGA microparticles to semi-solvents in the vapor phase demonstrated significant advantages over using semi-solvents in the liquid phase, such as in control of exposure conditions, access to imaging, decreasing the time for sequential exposure of semi-solvents, and using the same microparticles. The SSV approach for morphological analysis provides another tool to enhance our understanding of the microstructural arrangement of PLGA polymers. It will improve our comprehensive understanding of the factors controlling drug release from LAI formulations based on PLGA polymers.

Printed asymmetric microcapsules: Facile loading and multiple stimuli-responsiveness

Engineering of colloidal particles and capsules despite substantial progress is still facing a number of unsolved issues including low loading capacity, non-uniform size and shape of carriers, tailoring different functionalities and versatility to encapsulated cargo. In this work, we propose a method for defined-shaped functionally asymmetric polymer capsule fabrication based on a soft lithography approach. The developed capsules consist of two classes of polymers - the main part "cup" is made out of polyelectrolyte multilayers (PAH-PSS) and "lid" is made of biodegradable polyether (PLGA). Asymmetric capsules combine advantages from both traditional layer-by-layer capsules and recently developed printed "pelmeni" capsules. This combination provides stimuli-responsiveness due to polyelectrolyte multilayer properties differing from PLGA. The inner volume of capsules can be loaded with a variety of active compounds and the capsule's geometry is defined due to the soft-lithography method. Capsules have a core-shell structure and monodisperse size distribution. Three methods to trigger cargo release have been demonstrated, namely temperature treatment, ultrasonication and pH shift. Steroidal drug dexamethasone was used to illustrate the applicability of the systems for triggered drug release. The application of proposed asymmetric capsules includes but is not limited to pharmacology, diagnostics, sensors, micro- and nanoreactors and chemical actuators.

Redefining the importance of polylactide-co-glycolide acid (PLGA) in drug delivery

The limitations of non-biodegradable polymers have paved the way for biodegradable polymers in the pharmaceutical and biomedical sciences over the years. Poly (lactic-co-glycolic acid) (PLGA), also known as 'Smart polymer', is one of the most successfully developed biodegradable polymers due to its favorable properties, such as biodegradability, biocompatibility, controllable drug release profile, and ability to alter surface with targeting agents for diagnosis and treatment. The release behavior of drugs from PLGA delivery devices is influenced by the physicochemical properties of PLGA. In this review, the current state of the art of PLGA, its synthesis, physicochemical properties, and degradation are discussed to enunciate the boundaries of future research in terms of its applicability with the optimized design in today's modern age. The fundamental objective of this review is to highlight the significance of PLGA as a polymer in the field of cancer, cardiovascular diseases, neurological disorders, dentistry, orthopedics, vaccine therapy, theranostics and lastly emerging epidemic diseases like COVID-19. Furthermore, the coverage of recent PLGA-based drug delivery systems including nanosystems, microsystems, scaffolds, hydrogels, etc. has been summarized. Overall, this review aims to disseminate the PLGA-driven revolution of the drug delivery arena in the pharmaceutical and biomedical industry and bridge the lacunae between material research, preclinical experimentation, and clinical reality.

Recent Progress in Drug Release Testing Methods of Biopolymeric Particulate System

Biopolymeric microparticles have been widely used for long-term release formulations of short half-life chemicals or synthetic peptides. Characterization of the drug release from microparticles is important to ensure product quality and desired pharmacological effect. However, there is no official method for long-term release parenteral dosage forms. Much work has been done to develop methods for in vitro drug release testing, generally grouped into three major categories: sample and separate, dialysis membrane, and continuous flow (flow-through cell) methods. In vitro drug release testing also plays an important role in providing insight into the in vivo performance of a product. In vitro release test with in vivo relevance can reduce the cost of conducting in vivo studies and accelerate drug product development. Therefore, investigation of the in vitro-in vivo correlation (IVIVC) is increasingly becoming an essential part of particulate formulation development. This review summarizes the principles of the in vitro release testing methods of biopolymeric particulate system with the recent research articles and discusses their characteristics including IVIVC, accelerated release testing methods, and stability of encapsulated drugs.

Accelerated in vitro release testing method for a long-acting peptide-PLGA formulation

Poly (lactic-co-glycolic acid) (PLGA), a biocompatible and biodegradable polymer, is one of the most commonly used vehicles for controlled-release (CR) implantable dosage forms. Drug molecules formulated in such CR vehicles are released slowly over an extended period of time - often months to years - posing challenges for batch release and quality control testing. Thus, reliable and reproducible accelerated testing methods are required to bridge this gap during early formulation development. This work describes the development of an accelerated in vitro release testing method to predict the real-time in vitro release of a synthetic peptide from a 6-month CR PLGA implant formulation. While accelerated methods have been previously reported for PLGA-based formulations, this work describes a unique case of an aggregation-prone peptide, which required careful attention to the impact of different conditions on both release kinetics and peptide stability. This method describes a suitable combination of release conditions that could help in understanding the release profiles of such peptides prone to aggregation. Parameters including pH, buffer species, temperature, and addition of organic co-solvents and surfactants were evaluated separately and in combination for their ability to achieve complete peptide release within 2 weeks while accurately recapitulating release rate, profile and peptide stability. The accelerated release method that gave the best agreement with real-time release was a mixed media of co-solvent (5% tetrahydrofuran), surfactant (5% TritonX-100) and elevated temperature (50 °C) in a neutral buffer (PBS pH 7.4). This optimized accelerated release method achieved complete release of the peptide load within 14-21 days compared to 3- to 6-months of real-time release and could discriminate critical differences in release behavior between different CR formulations to guide formulation and process development.

Influence of PLGA molecular weight distribution on leuprolide release from microspheres

Poly (lactide-co-glycolide) (PLGA) is a biodegradable copolymer used in many long-acting drug products. The objective of the present study was to investigate the influence of polymer molecular weight distribution differences of PLGA on the in vitro release profile of leuprolide acetate microspheres. Eight microsphere formulations were prepared using the same manufacturing process but with different PLGA polymers. The physicochemical properties (drug loading, particle size and morphology) as well as the in vitro release profiles of the prepared microspheres were evaluated using a sample-and-separate method. The amount of burst release increased with increasing amount of low molecular weight fractions of PLGA, indicating that the drug release profiles appeared to be affected not only by the average molecular weight but also the molecular weight distribution of PLGA. In conclusion, quality control of the molecular weight distribution of PLGA as well as the weight average molecular weight is highly desirable in order to control the burst release.

pH-dependent delivery of chlorhexidine from PGA grafted mesoporous silica nanoparticles at resin-dentin interface

Background

A low pH environment is created due to the production of acids by oral biofilms that further leads to the dissolution of hydroxyapatite crystal in the tooth structure significantly altering the equilibrium. Although the overall bacterial counts may not be eradicated from the oral cavity, however, synthesis of engineered anti-bacterial materials are warranted to reduce the pathogenic impact of the oral biofilms. The purpose of this study was to synthesize and characterize chlorhexidine (CHX)-loaded mesoporous silica nanoparticles (MSN) grafted with poly-L-glycolic acid (PGA) and to test the in vitro drug release in various pH environments, cytotoxicity, and antimicrobial capacity. In addition, this study aimed to investigate the delivery of CHX-loaded/MSN-PGA nanoparticles through demineralized dentin tubules and how these nanoparticles interact with tooth dentin after mixing with commercial dentin adhesive for potential clinical application.

Results

Characterization using SEM/TEM and EDX confirmed the synthesis of CHX-loaded/MSN-PGA. An increase in the percentage of drug encapsulation efficiency from 81 to 85% in CHX loaded/MSN and 92–95% in CHX loaded/MSN-PGA proportionately increased with increasing the amount of CHX during the fabrication of nanoparticles. For both time-periods (24 h or 30 days), the relative microbial viability significantly decreased by increasing the CHX content (P < 0.001). Generally, the cell viability percentage of DPSCs exposed to MSN-PGA/Blank, CHX-loaded/MSN, and CHX-loaded/MSN-PGA, respectively was > 80% indicating low cytotoxicity profiles of experimental nanoparticles. After 9 months in artificial saliva (pH 7.4), the significantly highest micro-tensile bond strength value was recorded for 25:50 CHX/MSN and 25:50:50 CHX/MSN-PGA. A homogenous and widely distributed 50:50:50 CHX-loaded/MSN-PGA nanoparticles exhibited excellent bonding with the application of commercially available dentin adhesive.

Conclusions

A pH-sensitive CHX release response was noted when loaded in MSN grafted PGA nanoparticles. The formulated drug-loaded nanocarrier demonstrated excellent physicochemical, spectral, and biological characteristics. Showing considerable capacity to penetrate effectively inside dentinal tubules and having high antibacterial efficacy, this system could be potentially used in adhesive and restorative dentistry.

In-vitro drug release testing of parenteral formulations via an agarose gel envelope to closer mimic tissue firmness

Current in vitro drug-release testing of the sustained-release parenterals represents the in vivo situation insufficiently. In this work, a thin agarose hydrogel layer surrounding the tested dosage form was proposed to mimic the tissue. The method was applied on implantable formulations of different geometries (films, microspheres, and cylindrical implants); prepared from various polymers (several Resomer® grades or ethyl cellulose) and loaded with different model drugs: flurbiprofen, lidocaine or risperidone. The hydrogel layer did not possess any retarding effect on the released drug and acted as a physical restriction to swelling and/or plastic deformation of the tested dosage forms. This led to a different surface area available for drug-release compared with testing in release medium alone and correspondingly to significantly different release profiles of the majority of the formulations obtained between the two methods (e.g. t50% = 18 days in pure release medium vs. t50% = 26 days in gel-setup for risperidone loaded Resomer® 503 H films or t50% = 7 days vs. t50% = 19 days for risperidone loaded Resomer® 503 H microspheres). The limited space for swelling and the rigidity of the agarose gel might mimic the tight encapsulation of the dosage form in the tissue better than the conventional liquid medium.

Timeline of Translational Formulation Technologies for Cancer Therapy: Successes, Failures, and Lessons Learned Therefrom

Over the past few decades, the field of cancer therapy has seen a significant change in the way in which formulations are designed and developed, resulting in more efficient products that allow us to ultimately achieve improved drug bioavailability, efficacy, and safety. However, although many formulations have entered the market, many others have fallen by the wayside leaving the scientific community with several lessons to learn. The successes (and failures) achieved with formulations that have been approved in Europe and/or by the FDA for the three major types of cancer therapy (peptide-based therapy, chemotherapy, and radiotherapy) are reviewed herein, covering the period from the approval of the first prolonged-release system for hormonal therapy to the appearance of the first biodegradable microspheres intended for chemoembolization in 2020. In addition, those products that have entered phase III clinical trials that have been active over the last five years are summarized in order to outline future research trends and possibilities that lie ahead to develop clinically translatable formulations for cancer treatment.

Incorporation of doxorubicin in different polymer nanoparticles and their anticancer activity

Background: Nanoparticles are under investigation as carrier systems for anticancer drugs. The expression of efflux transporters such as the ATP-binding cassette (ABC) transporter ABCB1 is an important resistance mechanism in therapy-refractory cancer cells. Drug encapsulation into nanoparticles has been shown to bypass efflux-mediated drug resistance, but there are also conflicting results. To investigate whether easy-to-prepare nanoparticles made of well-tolerated polymers may circumvent transporter-mediated drug efflux, we prepared poly(lactic-co-glycolic acid) (PLGA), polylactic acid (PLA), and PEGylated PLGA (PLGA-PEG) nanoparticles loaded with the ABCB1 substrate doxorubicin by solvent displacement and emulsion diffusion approaches and assessed their anticancer efficiency in neuroblastoma cells, including ABCB1-expressing cell lines, in comparison to doxorubicin solution. Results: The resulting nanoparticles covered a size range between 73 and 246 nm. PLGA-PEG nanoparticle preparation by solvent displacement led to the smallest nanoparticles. In PLGA nanoparticles, the drug load could be optimised using solvent displacement at pH 7 reaching 53 µg doxorubicin/mg nanoparticle. These PLGA nanoparticles displayed sustained doxorubicin release kinetics compared to the more burst-like kinetics of the other preparations. In neuroblastoma cells, doxorubicin-loaded PLGA-PEG nanoparticles (presumably due to their small size) and PLGA nanoparticles prepared by solvent displacement at pH 7 (presumably due to their high drug load and superior drug release kinetics) exerted the strongest anticancer effects. However, nanoparticle-encapsulated doxorubicin did not display increased efficacy in ABCB1-expressing cells relative to doxorubicin solution. Conclusion: Doxorubicin-loaded nanoparticles made by different methods from different materials displayed substantial discrepancies in their anticancer activity at the cellular level. Optimised preparation methods resulted in PLGA nanoparticles characterised by increased drug load, controlled drug release, and high anticancer efficacy. The design of drug-loaded nanoparticles with optimised anticancer activity at the cellular level is an important step in the development of improved nanoparticle preparations for anticancer therapy. Further research is required to understand under which circumstances nanoparticles can be used to overcome efflux-mediated resistance in cancer cells.

Polymer Distribution and Mechanism Conversion in Multiple Media of Phase-Separated Controlled-Release Film-Coating

Phase-separated films of water-insoluble ethyl cellulose (EC) and water-soluble hydroxypropyl cellulose (HPC) can be utilized to tailor drug release from coated pellets. In the present study, the effects of HPC levels and the pH, type, ionic strength and osmolarity of the media on the release profiles of soluble metoprolol succinates from the EC/HPC-coated pellets were investigated, and the differences in drug-release kinetics in multiple media were further elucidated through the HPC leaching and swelling kinetics of the pellets, morphology (SEM) and water uptake of the free films and the interaction between the coating polymers and the media compositions. Interestingly, the drug release rate from the pellets in different media was not in agreement with the drug solubility which have a positive correlation with the drug dissolution rate based on Noyes–Whitney equation law. In particular, the drug release rate in acetate buffer at pH 4.5 was faster than that in other media despite the solubility of drug was relatively lower, regardless of the HPC levels. It may be attributed to the mutual effect between the EC and acetate buffer, which improved the permeability of the film. In contrast, the release of drug in HCl solution was dependent on the HPC levels. Increasing the levels of HPC increased the effects of hydrogen ions on the polymer of HPC, which resulted in a lower viscosity and strength of the gel, forming the larger size of pores in polymer films, thus increasing the drug diffused from the coating film. Further findings in phosphate buffer showed a reduction in the drug release compared to that in other media, which was only sensitive to the osmolarity rather than the HPC level and pH of the buffer. Additionally, a mathematical theory was used to better explain and understand the experimentally measured different drug release patterns. In summary, the study revealed that the effects of the media overcompensated that of the drug solubility to some extent for controlled-release of the coating polymers, and the drug release mechanism in multiple media depend on EC and HPC rather than on HPC alone, which may have a potential to facilitate the optimization of ideally film-coated formulations.

Electrospun PLGA membrane incorporated with andrographolide-loaded mesoporous silica nanoparticles for sustained antibacterial wound dressing

Aim: To assess the wound-healing ability of poly(lactic-co-glycolic acid) (PLGA) nanofibrous wound dressing incorporated with andrographolide (Andro)-loaded mesoporous silica nanoparticles (MSNs). Materials & methods: PLGA/Andro-MSNs nanofibrous membrane wound dressings were produced by electrospinning. The effects of MSNs on the hydrophilicity, degradation and mechanical strength of membranes were evaluated. The cumulative release of Andro in vitro was obtained. Cell culture and in vivo tests on infectious models were carried out. Results: The PLGA/Andro-MSNs membrane showed a sustained release of Andro. The incorporation of MSNs into PLGA improved the hydrophilicity of the nanofibrous membranes. Cell culture and in vivo tests showed that PLGA/Andro-MSNs membrane can promote epidermal cell adhesion and reduce inflammation process. Conclusion: PLGA/Andro-MSNs nanofibrous membrane exhibited an efficient wound-healing ability.

Comparing human peritoneal fluid and phosphate-buffered saline for drug delivery: do we need bio-relevant media?

An understanding of biological fluids at the site of administration is important to predict the fate of drug delivery systems in vivo. Little is known about peritoneal fluid; therefore, we have investigated this biological fluid and compared it to phosphate-buffered saline, a synthetic media commonly used for in vitro evaluation of intraperitoneal drug delivery systems. Human peritoneal fluid samples were analysed for electrolyte, protein and lipid levels. In addition, physicochemical properties were measured alongside rheological parameters. Significant inter-patient variations were observed with regard to pH (p < 0.001), buffer capacity (p < 0.05), osmolality (p < 0.001) and surface tension (p < 0.05). All the investigated physicochemical properties of peritoneal fluid differed from phosphate-buffered saline (p < 0.001). Rheological examination of peritoneal fluid demonstrated non-Newtonian shear thinning behaviour and predominantly exhibited the characteristics of an entangled network. Inter-patient and inter-day variability in the viscosity of peritoneal fluid was observed. The solubility of the local anaesthetic lidocaine in peritoneal fluid was significantly higher (p < 0.05) when compared to phosphate-buffered saline. Interestingly, the dissolution rate of lidocaine was not significantly different between the synthetic and biological media. Importantly, and with relevance to intraperitoneal drug delivery systems, the sustained release of lidocaine from a thermosensitive gel formulation occurred at a significantly faster rate into peritoneal fluid. Collectively, these data demonstrate the variation between commonly used synthetic media and human peritoneal fluid. The differences in drug release rates observed illustrate the need for bio-relevant media, which ultimately would improve in vitro-in vivo correlation.

Indomethacin functionalised poly(glycerol adipate) nanospheres as promising candidates for modified drug release

The linear polyester poly(glycerol adipate) (PGA) with its free pendant hydroxyl groups was covalently grafted with indomethacin which yields polymeric prodrugs. It was possible to produce nanospheres with narrow particle size distribution of these polymer-drug conjugates with an optimized interfacial deposition method. Nanospheres were characterized by zeta potential measurements, dynamic light scattering, electron microscopy and nanoparticle tracking analysis. Moreover, cell viability studies and cytotoxicity tests in three different cell lines were carried out showing low toxicity for three different degrees of grafting. In addition, the nanospheres had (in contrast to the free drug) low hemolytic activity in vitro. Release studies of nanodispersions are challenging. The use of a specially developed setup with highly porous aluminum oxide membranes enabled us to overcome problems associated with other setups (e.g. dialysis membranes). A slow and controlled release profile without any burst was observed over 15 days. The results indicate that indomethacin-PGA conjugates can be formulated successfully as nanospheres with the desired characteristics of small size with narrow distribution, controlled drug release and low toxicity. The newly developed particles have the potential to improve the therapy of inflammation and associated diseases.

Long-Acting Release Microspheres Containing Novel GLP-1 Analog as an Antidiabetic System

Glucagon-like peptide 1 (GLP-1) has recently received significant attention as an efficacious way to treat diabetes mellitus. However, the short half-life of the peptide limits its clinical application in diabetes. In our previous study, a novel GLP-1 analog (PGLP-1) with a longer half-life was synthesized and evaluated. Herein, we prepared the PGLP-1-loaded poly(d,l-lactide- co-glycolide) microspheres to achieve long-term effects on blood glucose control. The incorporation of zinc ion into the formulation can effectively decrease the initial burst release, and a uniform drug distribution was obtained, in contrast to native PGLP-1 encapsulated microspheres. We demonstrated that the solubility of the drug encapsulated in microspheres played an important role in in vitro release behavior and drug distribution inside the microspheres. The Zn-PGLP-1 microspheres had a prominent acute glucose reduction effect in the healthy mice. A hypoglycemic effect was observed in the streptozotocin (STZ) induced diabetic mice through a 6-week treatment of Zn-PGLP-1-loaded microspheres. Meanwhile, the administration of Zn-PGLP-1 microspheres led to the β-cell protection and stimulation of insulin secretion. The novel GLP-1 analog-loaded sustained microspheres may greatly improve patient compliance along with a desirable safety feature.

Design and characterization of hydrogel nanoparticles with tunable network characteristics for sustained release of a VEGF-mimetic peptide

Peptides that mimic the bioactivity of growth factors are rapidly emerging as therapeutics for a variety of drug delivery applications including therapeutic neovascularization. Neovascularization requires controlled and sustained delivery of proangiogenic factors to stimulate reperfusion of ischemic tissues. To this end, hydrogel nanoparticles were designed to provide sustained and tunable diffusion-based release of a pro-angiogenic peptide, QK. Inverse phase mini-emulsion polymerization (IPMP) was used to generate crosslinked poly(ethylene) glycol (PEG) hydrogel nanoparticles entrapped with the QK peptide. Peptide release kinetics were tuned through adjustments in nanoparticle crosslink density. This was achieved by altering the mole fraction of the crosslinking agent which allowed for the synthesis of low crosslink density (0.754 mmol cm^-3) and high crosslink density (0.810 mmol cm^-3) nanoparticles. Nanoparticle tracking analysis revealed narrow particle size distributions and similar particle sizes regardless of crosslink density (225 ± 75 nm and 233 ± 73 nm, for low and high crosslink density nanoparticles, respectively). The zeta potential was found to be -26 mV for blank nanoparticles and +4 mV in the case of QK-loaded nanoparticles. The resulting nanoparticle crosslink density impacted both peptide loading as well as release kinetics. In terms of cumulative fractional release and weight of peptide released per mass of nanoparticle, higher crosslink density nanoparticles resulted in slower peptide release kinetics. The IPMP process preserved the QK secondary structure and its bioactivity as confirmed using circular dichroism spectroscopy and a Matrigel tubulogenesis assay, respectively, with released peptide. The presented nanoparticles hold great potential for use as drug delivery carriers for stimulation of therapeutic neovascularization of ischemic tissues.

Preparation of TPP-crosslinked chitosan microparticles by spray drying for the controlled delivery of progesterone intended for estrus synchronization in cattle

PURPOSE

Planned reproduction in cattle involves regulation of estrous cycle and the use of artificial insemination. Cycle control includes the administration of exogenous progesterone during 5-8 days in a controlled manner allowing females to synchronize their ovulation. Several progesterone delivery systems are commercially available but they have several drawbacks. The aim of the present contribution was to evaluate chitosan microparticles entrapping progesterone as an alternative system.

METHODS

Microparticles were prepared by spray drying. The effect of formulation parameters and experimental conditions on particle features and delivery was studied. A mathematical model to predict progesterone plasma concentration in animals was developed and validated with experimental data.

RESULTS

Microparticle size was not affected by formulation parameters but sphericity enhances as Tween 80 content increases and it impairs as TPP content rises. Z potential decreases as phosphate content rises. Particles remain stable in acidic solution but the addition of surfactant is required to stabilize dispersions in neutral medium. Encapsulation efficiencies was 69-75%. In vitro delivery studies showed burst and diffusion-controlled phases, being progesterone released faster at low pH. In addition, delivery extend in cows was affected mainly by particle size and hormone initial content, while the amount injected altered plasma concentration. Theoretical predictions with excellent accuracy were obtained.

CONCLUSION

The mathematical model developed can help to find proper particle features to reach specific delivery rates in the animals. This not only save time, money and effort but also minimized experimentation with animals which is desired from an ethical point of view.

PLGA-based nanofibers with a biomimetic polynoradrenaline sheath for rapid in vivo sampling of tetrodotoxin and sulfonamides in pufferfish

PLGA nanofibers with PNA sheath modification achieve enhanced extraction performance and antibiofouling capacity for in vivo sampling in pufferfish.

Fabrication and Use of Poly(d,l-lactide-co-glycolide)-Based Formulations Designed for Modified Release of 5-Fluorouracil

5-fluorouracil (5-FU) is a chemotherapeutic agent that has been used for the treatment of a variety of malignancies since its initial introduction to the clinic in 1957. Owing to its short biological half-life, multiple dosings are generally required to maintain effective 5-FU plasma concentrations throughout the therapeutic period. Clinical studies have shown that continuous 5-FU administration is generally superior to bolus injection as exhibited by lower toxicities and increased therapeutic efficacy. Optimal therapeutic efficacy, however, is often compromised by the limiting therapeutic index. Whilst oral formulations are also used, these suffer from the drawbacks of variable bioavailability and first-pass metabolism. As a result, sustained release formulations of 5-FU have been investigated in an effort to mimic the kinetics of continuous infusion particularly for situations where local delivery is considered appropriate. The biocompatible, biodegradable, and highly tunable synthetic polymer, poly(d,l-lactide-co-glycolide) (PLGA), is widely used as a vector for sustained drug delivery, however, issues such as insufficient loading and inappropriate burst release kinetics have dogged progress into the clinic for small hydrophilic drugs such as 5-FU. This review provides introductory information about the mechanism of action, pharmacokinetic and physicochemical properties, and clinical use of 5-FU that have contributed to the development of PLGA-based 5-FU release platforms. In addition, this review provides information on fabrication methods used for a range of 5-FU-loaded PLGA formulations and discusses factors affecting the release kinetics of 5-FU as well as the in vitro and in vivo antitumor or antiproliferative efficacy of these platforms.

Effect of nonionic surfactants in release media on accelerated in-vitro release profile of sirolimus eluting stents with biodegradable polymeric coating

It is a well-known fact that sirolimus (SRL) undergoes degradation process via hydrolysis in aqueous media, leading to incorrect assessment of drug amount and thus release characteristics of formulations. The main objective of the present study was to evaluate the effect of nonionic surfactants in media on in-vitro release profiles for sirolimus eluting stents (SES) coated with biodegradable polymeric matrix. Phosphate buffer and acetate buffer incorporating nonionic surfactants with varying concentrations were examined for adequate solubility and stability (by RP-HPLC). Good sink condition was achieved in phosphate buffer (at pH 4.0) with 1.0% Tween 20, 1.0% Brij 35% and 0.5% Brij 58. Hydrodynamic size (by DLS) and the micelle-water partition coefficient (P) with standard free energy of solubilization (∆G_s°) of drug were evaluated to get some understanding about the solubilization phenomena. About 80% of drug release during the period of 48 h was achieved in optimized drug release media which was 1.0% Tween 20 in phosphate buffer pH 4.0. The obtained accelerated SRL release profile in optimized medium correlated well with the real time in-vitro release in phosphate buffer (pH 7.4). Surface morphology changes (by SEM), changes in gravimetric weights and molecular weight change (by GPC) were examined before and after drug release to understand the drug release mechanism which explains that the polymer did not undergo degradation during the drug release.

Opioid Addiction: Social Problems Associated and Implications of Both Current and Possible Future Treatments, including Polymeric Therapeutics for Giving Up the Habit of Opioid Consumption

BACKGROUND

Detoxification programmes seek to implement the most secure and compassionate ways of withdrawing from opiates so that the inevitable withdrawal symptoms and other complications are minimized. Once detoxification has been achieved, the next stage is to enable the patient to overcome his or her drug addiction by ensuring consumption is permanently and completely abandoned, only after which can the subject be regarded as fully recovered.

METHODS

A systematic search on the common databases of relevant papers published until 2016 inclusive.

RESULTS AND CONCLUSION

Our study of the available oral treatments for opioid dependence has revealed that no current treatment can actually claim to be fully effective. These treatments require daily oral administration and, consequently, regular visits to dispensaries, which in most cases results in a lack of patient compliance, which causes fluctuations in drug plasma levels. We then reviewed alternative treatments in the available scientific literature on polymeric sustained release formulations. Research has been done not only on release systems for detoxification but also on release systems for giving up the habit of taking opioids. These efforts have obtained the recent authorization of polymeric systems for use in patients that could help them to reduce their craving for drugs.

Drug loaded poly(glycerol sebacate) as a local drug delivery system for the treatment of periodontal disease

A simple, cost-efficient method to load drugs into poly(glycerol sebacate) polymer. Drugs were able to sustained release for up to 60 days. The drugs loaded polymer showed cytocompatibility and antimicrobial activities.

Evaluation of PLGA containing anti-CTLA4 inhibited endometriosis progression by regulating CD4+CD25+Treg cells in peritoneal fluid of mouse endometriosis model

Our study investigated poly(lactic-co-glycolic acid) (PLGA) as protein delivery vehicles encapsulate CTLA-4-antibody (anti-CTLA-4) which is essential for CD4+CD25+Treg cells suppressive function exposing superior potential for inhibiting endometriosis progress in mouse model than single anti-CTLA-4. Anti-CTLA-4 loaded PLGA combined to ligands CTLA-4 in surface of CD4+CD25+Treg cells which distributed in peritoneal fluid of mouse endometriosis model. The particle size, zeta potential of the anti-CTLA-4 loaded nanoparticles was detected by dynamic light scattering. Morphology of nanoparticles was evaluated by transmission electron microscopy (TEM). Confocal laser scanning microscopy (CLSM) indicated distribution of anti-CTLA-4 with PLGA or without in peritoneal fluid. Cumulative anti-CTLA-4 release from nanoparticles was evaluated by Micro BCA assay. The percentage of CD4+CD25+Treg cells in peritoneal fluid was demonstrated by flow cytometer. In vitro experiment we co-culture ectopic endometrial cells (EEC) with isolated CD4+CD25+Treg cells in peritoneal fluid (PF), proliferation and invasion of ectopic endometrial cells (EEC) was measured by BrdU ELISA assay and Matrigel invasion assay. In comparison with anti-CTLA-4 without nanoparticles, the bioconjugates PLGA/anti-CTLA-4 were tolerated in peritoneal fluid with a controlled release of anti-CTLA-4 in 3, 7, 14days. Moreover, PLGA/anti-CTLA-4 had superior protective regulation ability to reduce level of CD4+CD25+Treg cells in peritoneal fluid. Most strikingly, in vitro experiment, PLGA/anti-CTLA-4 exhibited better ability in inhibiting proliferation and invasion of ectopic endometrial cells in co-culture system compared with anti-CTLA-4. Progressively, PLGA/anti-CTLA-4 had better suppressive activity to inhibited IL-10 and TGF-beta secreted by CD4+CD25+Treg cells which indicating that PLGA/anti-CTLA-4 suppressed cells proliferation and invasion through reduced IL-10 and TGF-beta production. Thus, PLGA/anti-CTLA-4 may be a potential strategy for endometriosis therapy.

Micro- and Macrostructured PLGA/Gelatin Scaffolds Promote Early Cardiogenic Commitment of Human Mesenchymal Stem Cells In Vitro

The biomaterial scaffold plays a key role in most tissue engineering strategies. Its surface properties, micropatterning, degradation, and mechanical features affect not only the generation of the tissue construct in vitro, but also its in vivo functionality. The area of myocardial tissue engineering still faces significant difficulties and challenges in the design of bioactive scaffolds, which allow composition variation to accommodate divergence in the evolving myocardial structure. Here we aimed at verifying if a microstructured bioartificial scaffold alone can provoke an effect on stem cell behavior. To this purpose, we fabricated microstructured bioartificial polymeric constructs made of PLGA/gelatin mimicking anisotropic structure and mechanical properties of the myocardium. We found that PLGA/gelatin scaffolds promoted adhesion, elongation, ordered disposition, and early myocardial commitment of human mesenchymal stem cells suggesting that these constructs are able to crosstalk with stem cells in a precise and controlled manner. At the same time, the biomaterial degradation kinetics renders the PLGA/gelatin constructs very attractive for myocardial regeneration approaches.

Controlled release of NELL-1 protein from chitosan/hydroxyapatite-modified TCP particles

NEL-like molecule-1 (NELL-1) is a novel osteogenic protein that showing high specificity to osteochondral cells. It was widely used in bone regeneration research by loading onto carriers such as tricalcium phosphate (TCP) particles. However, there has been little research on protein controlled release from this material and its potential application. In this study, TCP was first modified with a hydroxyapatite coating followed by a chitosan coating to prepare chitosan/hydroxyapatite-coated TCP particles (Chi/HA-TCP). The preparation was characterized by SEM, EDX, FTIR, XRD, FM and Zeta potential measurements. The NELL-1 loaded Chi/HA-TCP particles and the release kinetics were investigated in vitro. It was observed that the Chi/HA-TCP particles prepared with the 0.3% (wt/wt) chitosan solution were able to successfully control the release of NELL-1 and maintain a slow, steady release for up to 28 days. Furthermore, more than 78% of the loaded protein's bioactivity was preserved in Chi/HA-TCP particles over the period of the investigation, which was significantly higher than that of the protein released from hydroxyapatite coated TCP (HA-TCP) particles. Collectively, this study suggests that the osteogenic protein NELL-1 showed a sustained release pattern after being encapsulated into the modified Chi/HA-TCP particles, and the NELL-1 integrated composite of Chi/HA-TCP showed a potential to function as a protein delivery carrier and as an improved bone matrix for use in bone regeneration research.

An Accelerated Release Study to Evaluate Long-Acting Contraceptive Levonorgestrel-Containing in Situ Forming Depot Systems

Biodegradable polymer-based injectable in situ forming depot (ISD) systems that solidify in the body to form a solid or semisolid reservoir are becoming increasingly attractive as an injectable dosage form for sustained (months to years) parenteral drug delivery. Evaluation of long-term drug release from the ISD systems during the formulation development is laborious and costly. An accelerated release method that can effectively correlate the months to years of long-term release in a short time such as days or weeks is economically needed. However, no such accelerated ISD system release method has been reported in the literature to date. The objective of the current study was to develop a short-term accelerated in vitro release method for contraceptive levonorgestrel (LNG)-containing ISD systems to screen formulations for more than 3-month contraception after a single subcutaneous injection. The LNG-containing ISD formulations were prepared by using biodegradable poly(lactide-co-glycolide) and polylactic acid polymer and solvent mixtures containing N-methyl-2-pyrrolidone and benzyl benzoate or triethyl citrate. Drug release studies were performed under real-time (long-term) conditions (PBS, pH 7.4, 37 °C) and four accelerated (short-term) conditions: (A) PBS, pH 7.4, 50 °C; (B) 25% ethanol in PBS, pH 7.4, 50 °C; (C) 25% ethanol in PBS, 2% Tween 20, pH 7.4, 50 °C; and (D) 25% ethanol in PBS, 2% Tween 20, pH 9, 50 °C. The LNG release profile, including the release mechanism under the accelerated condition D within two weeks, correlated (r² ≥ 0.98) well with that under real-time conditions at four months.

Polymer degradation and drug delivery in PLGA-based drug-polymer applications: A review of experiments and theories

Poly (lactic-co-glycolic acid) (PLGA) copolymers have been broadly used in controlled drug release applications. Because these polymers are biodegradable, they provide an attractive option for drug delivery vehicles. There are a variety of material, processing, and physiological factors that impact the degradation rates of PLGA polymers and concurrent drug release kinetics. This work is intended to provide a comprehensive and collective review of the physicochemical and physiological factors that dictate the degradation behavior of PLGA polymers and drug release from contemporary PLGA-based drug-polymer products. In conjunction with the existing experimental results, analytical and numerical theories developed to predict drug release from PLGA-based polymers are summarized and correlated with the experimental observations. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1692-1716, 2017.