Preparation and in vitro degradation properties of polylactide microcapsules

Superparamagnetic iron oxide nanoparticles for their application in the human body: Influence of the surface

Iron oxide nanoparticles (IONs) are of great interest in nanomedicine for imaging, drug delivery, or for hyperthermia treatment. Although many research groups have focused on the synthesis and application of IONs in nanomedicine, little is known about the influence of the surface properties on the particles' behavior in the human body. This study analyzes the impact of surface coatings (dextran, polyvinyl alcohol, polylactide-co-glycolide) on the nanoparticles' cytocompatibility, agglomeration, degradation, and the resulting oxidative stress induced by the particle degradation. All particles, including bare IONs (BIONs), are highly cytocompatible (>70%) and show no significant toxicity towards smooth muscle cells. Small-angle X-ray scattering profiles visualize the aggregation behavior of nanoparticles and yield primary particle sizes of around 20 nm for the investigated nanoparticles. A combined experimental setup of dynamic light scattering and phenanthroline assay was used to analyze the long-term agglomeration and degradation profile of IONs in simulated body fluids, allowing fast screening of multiple candidates. All particles degraded in simulated endosomal and lysosomal fluid, confirming the pH-dependent dissolution. The degradation rate decreased with the shrinking size of particles leading to a plateau. The fastest Fe²⁺ release could be measured for the polyvinyl-coated IONs. The analytical setup is ideal for a quick preclinical study of IONs, giving often neglected yet crucial information about the behavior and toxicity of nanoparticles in the human body. Moreover, this study allows for the development and evaluation of novel ferroptosis-inducing agents.

Enzymes' Power for Plastics Degradation

Plastics are everywhere in our modern way of living, and their production keeps increasing every year, causing major environmental concerns. Nowadays, the end-of-life management involves accumulation in landfills, incineration, and recycling to a lower extent. This ecological threat to the environment is inspiring alternative bio-based solutions for plastic waste treatment and recycling toward a circular economy. Over the past decade, considerable efforts have been made to degrade commodity plastics using biocatalytic approaches. Here, we provide a comprehensive review on the recent advances in enzyme-based biocatalysis and in the design of related biocatalytic processes to recycle or upcycle commodity plastics, including polyesters, polyamides, polyurethanes, and polyolefins. We also discuss scope and limitations, challenges, and opportunities of this field of research. An important message from this review is that polymer-assimilating enzymes are very likely part of the solution to reaching a circular plastic economy.

Engineering and polymeric composition of drug-eluting suture: A review

Sutures are the most popular surgical implants in the global surgical equipment market. They are used for holding tissues together to achieve wound closure. However, controlling the body's immune response to these "foreign bodies" at site of infection is challenging. Natural polymers such as collagen, silk, nylon, and cotton, and synthetic polymers such as polycaprolactone, poly(lactic-co-glycolic acid), poly(p-dioxanone) and so forth, contribute the robust foundation for the engineering of drug-eluting sutures. The incorporation of active pharmaceutical ingredients (APIs) with polymeric composition of suture materials is an efficient way to reduce inflammatory reaction in the wound site as well as to control bacterial growth, while allowing wound healing. The incorporation of polymeric composition in surgical sutures has been found to add high flexibility as well as excellent physical and mechanical properties. Fabrication processes and polymer materials allow control over drug-eluting profiles to effectively address wound healing requirements. This review outlines and discusses (a) polymer materials and APIs used in suture applications, including absorbable and nonabsorbable sutures; (b) suture structures, such as monofilament, multifilament, barded and smart sutures; and (c) the existing manufacturing techniques for drug-eluting suture production, including electrospinning, melt-extrusion and coating.

Chemical Recycling of End-of-Life Poly(lactide) via Zinc-Catalyzed Depolymerization and Polymerization

The chemical recycling of poly(lactide) was investigated based on depolymerization and polymerization processes. Using methanol as depolymerization reagent and zinc salts as catalyst, poly(lactide) was depolymerized to methyl lactate applying microwave heating. An excellent performance was observed for zinc(II) acetate with turnover frequencies of up to 45000 h-1. In a second step the monomer methyl lactate was converted to (pre)poly(lactide) in the presence of catalytic amounts of zinc salts. Here zinc(II) triflate revealed excellent performance for the polymerization process (yield: 91 %, Mn ∼8970 g/mol). Moreover, the (pre)poly(lactide) was depolymerized to lactide, the industrial relevant molecule for accessing high molecular weight poly(lactide), using zinc(II) acetate as catalyst.

Ruthenium-Catalyzed Hydrogenative Degradation of End-of-Life Poly(lactide) to Produce 1,2-Propanediol as Platform Chemical

The chemical recycling of end-of-life polymers can add some value to a future circular economy. In this regard, the hydrogenative degradation of end-of-life PLA was investigated to produce 1,2-propanediol as product, which is a useful building block in polymer chemistry. In more detail, the commercially available Ru-MACHO-BH complex was applied as catalyst to degrade end-of-life PLA efficiently to 1,2-propanediol under mild conditions. After investigations of the reaction conditions a set of end-of-life PLA goods were subjected to degradation.

Tin(ii) 2-ethylhexanoate catalysed methanolysis of end-of-life poly(lactide)

The depolymerisation of end-of-life poly(lactide) (PLA) goods was studied as part of the chemical recycling of PLA.

A hierarchical functionalized biodegradable PLA electrospun nanofibrous membrane with superhydrophobicity and antibacterial properties for oil/water separation

A hierarchical surface-modified biodegradable electrospun nanofibrous PLA membrane showed excellent superhydrophobicity and antibacterial properties for high-efficient oil/water separation.

Degradation, intra-articular retention and biocompatibility of monospheres composed of [PDLLA-PEG-PDLLA]-b-PLLA multi-block copolymers

In this study, we investigated the use of microspheres with a narrow particle size distribution ('monospheres') composed of biodegradable poly(DL-lactide)-PEG-poly(DL-lactide)-b-poly(L-lactide) multiblock copolymers that are potentially suitable for local sustained drug release in articular joints. Monospheres with sizes of 5, 15 and 30μm and a narrow particle size distribution were prepared by a micro-sieve membrane emulsification process. During in vitro degradation, less crystallinity, higher swelling and accelerated mass loss during was observed with increasing the PEG content of the polymer. The monospheres were tested in both a small (mice/rat) and large animal model (horse). In vivo imaging after injection with fluorescent dye loaded microspheres in mice knees showed that monospheres of all sizes retained within the joint for at least 90days, while the same dose of free dye redistributed to the whole body within the first day after intra-articular injection. Administration of monospheres in equine carpal joints caused a mild transient inflammatory response without any clinical signs and without degradation of the cartilage, as evidenced by the absence of degradation products of sulfated glycosaminoglycans or collagen type 2 in the synovial fluid. The excellent intra-articular biocompatibility was confirmed in rat knees, where μCT-imaging and histology showed neither changes in cartilage quality nor quantity. Given the good intra-articular retention and the excellent biocompatibility, these novel poly(DL-lactide)-PEG-poly(DL-lactide)-b-poly(L-lactide)-based monospheres can be considered a suitable platform for intra-articular drug delivery.

STATEMENT OF SIGNIFICANCE

This paper demonstrates the great potential in intra-articular drug delivery of monodisperse biodegradable microspheres which were prepared using a new class of biodegradable multi-block copolymers and a unique membrane emulsification process allowing the preparation of microspheres with a narrow particle size distribution (monospheres) leading to multiple advantages like better injectability, enhanced reproducibility and predictability of the in vivo release kinetics. We report not only on the synthesis and preparation, but also in vitro characterization, followed by in vivo testing of intra-articular biocompatibility of the monospheres in both a small and a large animal model. The favourable intra-articular biocompatibility combined with the prolonged intra-articular retention (>90days) makes these monospheres an interesting drug delivery platform. What should also be highlighted is the use of horses; a very accurate translational model for the human situation, making the results not only relevant for equine healthcare, but also for the development of novel human OA therapies.

Tamoxifen citrate-loaded poly(d,l) lactic acid nanoparticles: Evaluation for their anticancer activity in vitro and in vivo

The optimization of tamoxifen citrate entrapment and its release from biodegradable poly(d,l) lactic acid nanoparticles are prepared by modified spontaneous emulsification solvent diffusion method. Since the addition of tamoxifen citrate induces the formation of drug crystals from nanoparticle suspension the influence of several parameters on tamoxifen citrate encapsulation was investigated. In vitro studies for cytotoxicity, DNA ladder, and the expression of Bcl-2-Bax expression were also investigated for MCF-7 and MDA-MB-231 cells after the addition of tamoxifen citrate alone and tamoxifen citrate-poly(d,l) lactic acid-nanoparticles (encapsulated tamoxifen citrate). From results, it was noticed that the size and zeta potential of the drug loaded nanoparticles were not differed much in their physicochemical properties from drug free counterparts. The drug-loaded and drug-free nanoparticles exhibited size of in between 271.4 and 282.7 nm and zeta potential of -34 to -27.4 mV, respectively. There was significant increase in drug incorporation in the particles noticed in dichloromethane + methanol system in comparison to acetone + methanol and ethyl acetate + methanol systems. The drug was partly released from the nanoparticles after 48 h of incubation at 37℃. From Fourier transform infrared spectroscopy and differential scanning calorimetry data demonstrated drug-polymer characteristics within the nanoparticles and unincorporated drug that appeared in the form of crystals from polarized microscopic study. MCF-7 and MDA-MB-231 cells were more sensitive to tamoxifen citrate-poly(d,l) lactic acid-nanoparticles than tamoxifen citrate alone. DNA ladder and the expression of Bax to Bcl-2 ratio were much higher in tamoxifen citrate encapsulated in nanoparticles than that in tamoxifen citrate alone. These results demonstrated the feasibility of encapsulation of tamoxifen citrate and its enhanced efficiency in vitro and in vivo studies.

Monitoring of the Enzymatically Catalyzed Degradation of Biodegradable Polymers by Means of Capacitive Field-Effect Sensors

Designing novel or optimizing existing biodegradable polymers for biomedical applications requires numerous tests on the effect of substances on the degradation process. In the present work, polymer-modified electrolyte-insulator-semiconductor (PMEIS) sensors have been applied for monitoring an enzymatically catalyzed degradation of polymers for the first time. The thin films of biodegradable polymer poly(D,L-lactic acid) and enzyme lipase were used as a model system. During degradation, the sensors were read-out by means of impedance spectroscopy. In order to interpret the data obtained from impedance measurements, an electrical equivalent circuit model was developed. In addition, morphological investigations of the polymer surface have been performed by means of in situ atomic force microscopy. The sensor signal change, which reflects the progress of degradation, indicates an accelerated degradation in the presence of the enzyme compared to hydrolysis in neutral pH buffer media. The degradation rate increases with increasing enzyme concentration. The obtained results demonstrate the potential of PMEIS sensors as a very promising tool for in situ and real-time monitoring of degradation of polymers.

A short term quality control tool for biodegradable microspheres

Accelerated in vitro release testing methodology has been developed as an indicator of product performance to be used as a discriminatory quality control (QC) technique for the release of clinical and commercial batches of biodegradable microspheres. While product performance of biodegradable microspheres can be verified by in vivo and/or in vitro experiments, such evaluation can be particularly challenging because of slow polymer degradation, resulting in extended study times, labor, and expense. Three batches of Leuprolide poly(lactic-co-glycolic acid) (PLGA) microspheres having varying morphology (process variants having different particle size and specific surface area) were manufactured by the solvent extraction/evaporation technique. Tests involving in vitro release, polymer degradation and hydration of the microspheres were performed on the three batches at 55°C. In vitro peptide release at 55°C was analyzed using a previously derived modification of the Weibull function termed the modified Weibull equation (MWE). Experimental observations and data analysis confirm excellent reproducibility studies within and between batches of the microsphere formulations demonstrating the predictability of the accelerated experiments at 55°C. The accelerated test method was also successfully able to distinguish the in vitro product performance between the three batches having varying morphology (process variants), indicating that it is a suitable QC tool to discriminate product or process variants in clinical or commercial batches of microspheres. Additionally, data analysis utilized the MWE to further quantify the differences obtained from the accelerated in vitro product performance test between process variants, thereby enhancing the discriminatory power of the accelerated methodology at 55°C.

Synthesis and in vivo pharmacokinetic evaluation of degradable shell cross-linked polymer nanoparticles with poly(carboxybetaine) versus poly(ethylene glycol) surface-grafted coatings

Nanoparticles with tunable pharmacokinetics are desirable for various biomedical applications. Poly(ethylene glycol) (PEG) is well-known to create "stealth" effects to stabilize and extend the blood circulation of nanoparticles. In this work, poly(carboxybetaine) (PCB), a new nonfouling polymer material, was incorporated as surface-grafted coatings, conjugated onto degradable shell cross-linked knedel-like nanoparticles (dSCKs) composed of poly(acrylic acid)-based shells and poly(lactic acid) cores, to compare the in vivo pharmacokinetics to their PEG-functionalized analogues. A series of five dSCKs was prepared from amphiphilic block copolymers, having different numbers and lengths of either PEG or PCB grafts, by supramolecular assembly in water followed by shell cross-linking, and then studied by a lactate assay to confirm their core hydrolytic degradabilities. Each dSCK was also conjugated with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid macrocyclic chelators and tyramine moieties to provide for (64)Cu and/or radiohalogen labeling. The high specific activity of (64)Cu radiolabeling ensured nanogram administration of dSCKs for in vivo evaluation of their pharmacokinetics. Biodistribution studies demonstrated comparable in vivo pharmacokinetic profiles of PCB-grafted dSCKs to their PEG-conjugated counterparts. These results indicated that PCB-functionalized dSCKs have great potential as a theranostic platform for translational research.

Accelerated in-vitro release testing methods for extended-release parenteral dosage forms

OBJECTIVES

This review highlights current methods and strategies for accelerated in-vitro drug release testing of extended-release parenteral dosage forms such as polymeric microparticulate systems, lipid microparticulate systems, in-situ depot-forming systems and implants.

KEY FINDINGS

Extended-release parenteral dosage forms are typically designed to maintain the effective drug concentration over periods of weeks, months or even years. Consequently, 'real-time' in-vitro release tests for these dosage forms are often run over a long time period. Accelerated in-vitro release methods can provide rapid evaluation and therefore are desirable for quality control purposes. To this end, different accelerated in-vitro release methods using United States Pharmacopeia (USP) apparatus have been developed. Different mechanisms of accelerating drug release from extended-release parenteral dosage forms, along with the accelerated in-vitro release testing methods currently employed are discussed.

SUMMARY

Accelerated in-vitro release testing methods with good discriminatory ability are critical for quality control of extended-release parenteral products. Methods that can be used in the development of in-vitro-in-vivo correlation (IVIVC) are desirable; however, for complex parenteral products this may not always be achievable.

Sustained-release of protein from biodegradable sericin film, gel and sponge

A silk protein, sericin, contains 18 kinds of amino acids, mostly polar side chains forming a complex of three principal polypeptides. The major polypeptides exhibit hydrophobic characteristics by forming a β-sheet structure in a hydrate state. As a drug-releasing biomaterial made by an aqueous process without using any cross linker, sericin is expected to form various hydrophobic dosage forms. However, its dosage form, with respect to the molecular weight and concentration of sericin, and its biodegradation behavior has not been studied in detail. In this study, the film, gel and sponge of sericin were prepared and examined to determine the release properties of the charged protein, fluorescein isothiocyanate-albumin (FA). The film and gel, as solid and semisolid forms, respectively, were also evaluated for their biodegradation behavior. For in vitro release, FA was sustained-released from these preparations. The concentration and dosage form markedly affected FA release. For in vivo biodegradation, the sericin preparations implanted subcutaneously in rats gradually decreased in size and weight. Histological examination indicated no marked inflammation at the site. As for in vivo release, FA remained for 3-6 weeks or more in rats. These findings suggest that sericin is suitable for use as a drug-releasing biomaterial.

Branched poly(lactide) synthesized by enzymatic polymerization: effects of molecular branches and stereochemistry on enzymatic degradation and alkaline hydrolysis

In this article the effects of the number of molecular branches (chain ends) and the stereochemistry of poly(lactide)s (PLAs) on the enzymatic degradation and alkaline hydrolysis are studied. Various linear and branched PLAs were synthesized using lipase PS (Pseudomonas fluorescens)-catalyzed ring-opening polymerization (ROP) of lactide monomers having different stereochemistries (L-lactide, D-lactide, and D,L-lactide). Five different alcohols were used as initiators for the ROP, and the monomer-to-initiator molar feed ratio was varied from 10 to 100 and 1000 for each branch in the polymer architecture. The properties of branched PLAs that would affect the enzymatic and alkaline degradations, i.e., the glass transition temperature, the melting temperature, the melting enthalpy, and the advancing contact angle, were determined. The PLA films were degraded using proteinase K or 1.0 M NaOH solution, and the weight loss and changes in the number average molecular weight (Mn) of the polymer were studied during 12 h of degradation. The results suggest that an increase in the number of molecular branches of branched PLAs enhances its enzymatic degradability and alkali hydrolyzability. Moreover, the change in Mn of the branched poly(L-lactide) (PLLA) by alkaline hydrolysis indicated that the decrease in Mn was in the first place dependent on the number of molecular branches and thereafter on the length of the molecular branch of branched PLA. The branched PLLA, poly(D-lactide) (PDLA), and poly(D,L-lactide) (PDLLA) differed in weight loss and change in Mn of the PLA segment during the enzymatic degradation. It is suggested that the branched PDLLA was degraded preferentially by proteinase K.

5-Fluorouracil plasma levels and biodegradation of subcutaneously injected drug-loaded microspheres prepared by spray-drying poly(d,l-lactide) and poly(d,l-lactide-co-glycolide) polymers

Microspheres (MS) of 5-fluorouracil-loaded poly(D,L-lactide) (PLA), poly(D,L-lactide-co-glycolide) 75/25 (PLGA 75/25) and poly(D,L-lactide-co-glycolide) 50/50 (PLGA 50/50) prepared by the spray-drying technique were subcutaneously injected in the back of Wistar rats in order to evaluate the 5-fluorouracil (5-FU) release and the biodegradation characteristics. Determination of plasma 5-FU concentration by HPLC with analysis of data using a non-compartmental model showed drug in plasma between 9 and 14 days after administration of drug-loaded PLGA 50/50 or PLA and PLGA 75/25 microspheres, respectively, with a maximum drug concentration of 2.4+/-0.2microg/mL at 24h (5-FU-loaded PLGA 50/50 MS), 2.5+/-0.1microg/mL at 48h (5-FU-loaded PLGA 75/25 MS), and 2.3+/-0.1microg/mL at 24h (5-FU-loaded PLA MS). Pharmacokinetically, a significant increase of AUC (up to 50 times) and MRT (up to 196 times) of 5-FU with regard to the administration of the drug in solution was observed. Scanning electron microscopy and histological studies indicated that a small fibrous capsule was observed around the microspheres in the site of injection. One month after the injection of PLGA 50/50 MS and 2 months after the injection of PLGA 75/25 and PLA MS, masses of polymers, instead of single microspheres, were observed. Close to them, macrophagic cells were present, and blood vessels were observed in the connective tissue. Total absence of fibrous capsule and injected microspheres was observed after 2 (for PLGA 50/50 MS) or 3 (PLGA 75/25 and PLA MS) months.

Profiling in vitro drug release from subcutaneous implants: a review of current status and potential implications on drug product development

This review presents current methods and strategies for studying the release characteristics of drugs from subcutaneous implant dosage forms. Implants are dosage forms that are subcutaneously placed with the aid of surgery or a hypodermic needle, and are designed to release drugs over a prolonged period of time. In most cases, the objective of a release test is to identify sufficiently discriminatory procedures that in turn would provide data to set meaningful specifications. Additional information obtained from successful in vitro-in vivo correlations (IVIVC) and accelerated drug release tests are extremely useful during drug product development. Although several workers have employed different methods to monitor drug release from these dosage forms, the use of the compendial Apparatus 4 (flow-through) device has been recommended in a publication on FIP/AAPS Guidelines for drug release testing of modified release dosage forms. However, most of method development with this device has focused on oral immediate or controlled release dosage forms and little published information is available on implants. Two recent reports on workshops provide useful information on methods to evaluate drug release from controlled-release parenterals such as implants, including IVIVC and accelerated release testing. Details on such studies, however, are generally not found in the literature; possibly because of the high proprietary value of methodologies for establishing release specifications of implant dosage forms. This article reviews the current status of methodologies used in the investigation of drug release from subcutaneous implants with an emphasis on mechanistic, product development and regulatory perspectives.

A model-dependent approach to correlate accelerated with real-time release from biodegradable microspheres

The purpose of this study was to determine the feasibility of applying accelerated in vitro release testing to correlate or predict long-term in vitro release of leuprolide poly(lactide-co-glycolide) microspheres. Peptide release was studied using a dialysis technique at 37 degrees C and at elevated temperatures (50 degrees C-60 degrees C) in 0.1M phosphate buffered saline (PBS) pH 7.4 and 0.1M acetate buffer pH 4.0. The data were analyzed using a modification of the Weibull equation. Peptide release was temperature dependent and complete within 30 days at 37 degrees C and 3 to 5 days at the elevated temperatures. In vitro release profiles at the elevated temperatures correlated well with release at 37 degrees C. The shapes of the release profiles at all temperatures were similar. Using the modified Weibull equation, an increase in temperature was characterized by an increase in the model parameter, alpha, a scaling factor for the apparent rate constant. Complete release at 37 degrees C was shortened from approximately 30 days to 5 days at 50 degrees C, 3.5 days at 55 degrees C, 2.25 days at 60 degrees C in PBS pH 7.4, and 3 days at 50 degrees C in acetate buffer pH 4.0. Values for the model parameter beta indicated that the shape of the release profiles at 55 degrees C in PBS pH 7.4 (2.740) and 50 degrees C in 0.1M acetate buffer pH 4.0 (2.711) were similar to that at 37 degrees C (2.677). The E(a) for hydration and erosion were determined to be 42.3 and 19.4 kcal/mol, respectively. Polymer degradation was also temperature dependent and had an E(a) of 31.6 kcal/mol. Short-term in vitro release studies offer the possibility of correlation with long-term release, thereby reducing the time and expense associated with long-term studies. Accelerated release methodology could be useful in the prediction of long-term release from extended release microsphere dosage forms and may serve as a quality control tool for the release of clinical or commercial batches.

Impurity formation studies with peptide-loaded polymeric microspheres Part II. In vitro evaluation

Since acylated peptide impurities were isolated from octreotide microspheres following incubation in an in vivo environment, the present investigation was undertaken to determine the dosage form dynamics responsible for facilitating acylation. In particular, microsphere batches made with poly(L-lactide) (PLA) and poly(lactide-co-glycolide) (PLGA) 85:15 were studied for in vitro drug release, mass balance relationships, mass loss behavior, hydration uptake, and solid-state stability. Furthermore, native octreotide was incubated in a varying pH stability model (heat treated lactic acid solutions 42.5%, w/w) to determine the effects of acidity on impurity formation. From a review of the experimental results, the appearance of octreotide impurities or related substances occurred with the onset of polymeric mass loss. In fact, the significant formation of acylated peptide did not appear until >90% mass loss, which was observed at 14 days. It was surmised that because of water uptake, the hydrolytic cleavage of the polymeric backbone created an acidic microenvironment to facilitate the covalent coupling of peptide with polymer. The lactic acid solution stability model corroborated with greater evidence of acylation at pH 2.25 where the presence lactoyl (+72 m/z) derivatives of octreotide were confirmed by MALDI-TOF mass spectrometry.