A mechanistic Study on the Chemical and Enzymatic Degradation of PEG‐Oligo(ε‐caprolactone) Micelles

Enhanced biological properties of polyvinyl alcohol-polycaprolactone/hyaluronic acid-coated electrospun scaffolds for articular cartilage regeneration

This study provides a cohesive framework to putting forth PVA-PCL scaffolds coated with hyaluronic acid (HA) hydrogel to mimic the characteristics of articular cartilage, as a cost-effective tissue engineering alternative. PVA and PCL solutions were prepared and electrospun under measured conditions, with parameters adjusted to fabricate aligned and random fiber orientations. Afterward, the scaffold was integrated with the optimal hydrogel, selected for its superior water absorption and hydrophilicity. The thickness of the hydrogel layer satisfied the criteria for supporting chondrocyte function, and the study assesses its effect on cell viability. Scaffolds were characterized using field emission scanning electron microscopy (FE-SEM) for morphology, energy-dispersive X-ray spectroscopy (EDX) for elemental analysis, Fourier transform infrared (FTIR) spectroscopy for chemical composition, and tensile tests for mechanical behavior. The surface wettability was determined by contact angle measurements. Biological properties were assessed through cytotoxicity, protein absorption assays and cell adhesion tests with visualization of cell distribution using DAPI staining, fluorescence microscopy, and FE-SEM. Using a hydrolytic mechanism, biodegradation was assessed using pH variations and weight loss measurements. Accordingly, randomly oriented hydrogel-coated scaffolds yielded the most favorable biological outcomes to produce a tissue-friendly, biologically robust graft that closely mimics the natural cartilage extracellular matrix. The pore size and distribution of these scaffolds were more uniform than those of aligned structures. The findings suggest possibilities for customizing scaffold properties through fiber orientation, polymer blending, and surface coating to optimize cell response and tissue formation. Combining electrospun PVA-PCL with chondrocytes-seeded hydrogels offers a way to improve articular cartilage regeneration.

Near-Infrared Light-Responsive Molybdenum Disulfide Nanosheets for Controlling the Release of Nimodipine as NIR-Drug Delivery System

Here, we present a photothermally triggered drug delivery nanosystem MoS2-NIMO-CHIT-SH, using the thiolated chitosan (CHIT-SH)-modified molybdenum disulfide (MoS2) nanosheets as near-infrared (NIR) photo-responsive carriers, loaded with the dihydropyridine calcium antagonist drug Nimodipine (NIMO). Although NIMO is used to treat stroke, migraine, Alzheimer's disease, cerebrovascular spasms, and hypertension, this drug is poorly water-soluble, with low bioavailability and lack of selectivity. Thus, there is an urgent need for a novel approach to creating NIMO formulations that are safe, effective, and have better solubility and bioavailability. To overcome these problems, we develop a cationic biopolymer functionalized MoS2 nanosheets as a photothermal drug carrier system to facilitate the NIR light-induced release of NIMO drugs. MoS2 nanosheets (<150 nm) as NIMO drug carriers are prepared through simple exfoliation of their bulk phase and then functionalized with CHIT-SH biopolymer to increase their physiological stability and biocompatibility. According to the results, MoS2-NIMO-CHIT-SH nanocomposites show strong NIR absorbance, which makes them a promising candidate for photothermal therapy.

Investigations into the characterization, degradation, and applications of biodegradable polymers by mass spectrometry

Biodegradable polymers have been getting more and more attention because of their contribution to the plastic pollution environmental issues and to move towards a circular economy. Nevertheless, biodegradable materials still exhibit various disadvantages restraining a widespread use in the market. Therefore, additional research efforts are required to improve their performance. Mass spectrometry (MS) affords a relevant contribution to optimize biodegradable polymer synthesis, to confirm macromolecular structures, to examine along the time the progress of degradation processes and highlight advantages and drawbacks in the extensive applications. This review aims to provide an overview of the MS investigations carried out to support the synthesis of biodegradable polymers, with helpful information on undesirable products or polymerization mechanism, to understand deterioration pathways by the structure of degradation products and to follow drug release and pharmacokinetic. Additionally, it summarizes MS studies addressed on environmental and health issues related to the extensive use of plastic materials, that is, potential migration of additives or microplastics identification and quantification. The paper is focused on the most significant studies relating to synthetic and microbial biodegradable polymers published in the last 15 years, not including agro-polymers such as proteins and polysaccharides.

Amphiphilic Diblock Copolymers Bearing Poly(Ethylene Glycol) Block: Hydrodynamic Properties in Organic Solvents and Water Micellar Dispersions, Effect of Hydrophobic Block Chemistry on Dispersion Stability and Cytotoxicity

Despite the fact that amphiphilic block copolymers have been studied in detail by various methods both in common solvents and aqueous dispersions, their hydrodynamic description is still incomplete. In this paper, we present a detailed hydrodynamic study of six commercial diblock copolymers featuring the same hydrophilic block (poly(ethylene glycol), PEG; degree of polymerization is ca. 110 ± 25) and the following hydrophobic blocks: polystyrene, PS35-b-PEG115; poly(methyl methacrylate), PMMA55-b-PEG95; poly(1,4-butadyene), PBd90-b-PEG130; polyethylene PE40-b-PEG85; poly(dimethylsiloxane), PDMS15-b-PEG115; and poly(ɛ-caprolactone), PCL45-b-PEG115. The hydrodynamic properties of block copolymers are investigated in both an organic solvent (tetrahydrofuran) and in water micellar dispersions by the combination of static/dynamic light scattering, viscometry, and analytical ultracentrifugation. All the micellar dispersions demonstrate bimodal particle distributions: small compact (hydrodynamic redii, Rh ≤ 17 nm) spherical particles ascribed to "conventional" core-shell polymer micelles and larger particles ascribed to micellar clusters. Hydrodynamic invariants are (2.4 ± 0.4) × 10-10 g cm2 s-2 K-1 mol-1/3 for all types of micelles used in the study. For aqueous micellar dispersions, in view of their potential biomedical applications, their critical micelle concentration values and cytotoxicities are also reported. The investigated micelles are stable towards precipitation, possess low critical micelle concentration values (with the exception of PDMS15-b-PEG115), and demonstrate low toxicity towards Chinese Hamster Ovarian (CHO-K1) cells.

The in vivo fate of polymeric micelles

This review aims to provide a systemic analysis of the in vivo, as well as subcellular, fate of polymeric micelles (PMs), starting from the entry of PMs into the body. Few PMs are able to cross the biological barriers intact and reach the circulation. In the blood, PMs demonstrate fairly good stability mainly owing to formation of protein corona despite controversial results reported by different groups. Although the exterior hydrophilic shells render PMs "long-circulating", the biodistribution of PMs into the mononuclear phagocyte systems (MPS) is dominant as compared with non-MPS organs and tissues. Evidence emerges to support that the copolymer poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) is first broken down into pieces of PEG and PLA and then remnants to be eliminated from the body finally. At the cellular level, PMs tend to be internalized via endocytosis due to their particulate nature and disassembled and degraded within the cell. Recent findings on the effect of particle size, surface characteristics and shape are also reviewed. It is envisaged that unraveling the in vivo and subcellular fate sheds light on the performing mechanisms and gears up the clinical translation of PMs.

EGFR-Targeted Nanobody Functionalized Polymeric Micelles Loaded with mTHPC for Selective Photodynamic Therapy

meta-Tetra(hydroxyphenyl)chlorin (mTHPC) is one of the most potent second-generation photosensitizers, clinically used for photodynamic therapy (PDT) of head and neck squamous cell carcinomas. However, improvements are still required concerning its present formulation (i.e., Foscan, a solution of mTHPC in ethanol/propylene glycol (40:60 w/w)), as mTHPC has the tendency to aggregate in aqueous media, e.g., biological fluids, and it has limited tumor specificity. In the present study, polymeric micelles with three different diameters (17, 24, and 45 nm) based on benzyl-poly(ε-caprolactone)-b-poly(ethylene glycol) (PCL_n-PEG; n = 9, 15, or 23) were prepared with mTHPC loadings ranging from 0.5 to 10 wt % using a film-hydration method as advanced nanoformulations for this photosensitizer. To favor the uptake of the micelles by cancer cells that overexpress the epidermal growth factor receptor (EGFR), the micelles were decorated with an EGFR-targeted nanobody (named EGa1) through maleimide-thiol chemistry. The enhanced binding of the EGFR-targeted micelles at 4 °C to EGFR-overexpressing A431 cells, compared to low-EGFR-expressing HeLa cells, confirmed the specificity of the micelles. In addition, an enhanced uptake of mTHPC-loaded micelles by A431 cells was observed when these were decorated with the EGa1 nanobody, compared to nontargeted micelles. Both binding and uptake of targeted micelles were blocked by an excess of free EGa1 nanobody, demonstrating that these processes occur through EGFR. In line with this, mTHPC loaded in EGa1-conjugated PCL₂₃-PEG (EGa1-P₂₃) micelles demonstrated 4 times higher photocytotoxicity on A431 cells, compared to micelles lacking the nanobody. Importantly, EGa1-P₂₃ micelles also showed selective PDT against A431 cells compared to the low-EGFR-expressing HeLa cells. Finally, an in vivo pharmacokinetic study shows that after intravenous injection, mTHPC incorporated in the P₂₃ micelles displayed prolonged blood circulation kinetics, compared to free mTHPC, independently of the presence of EGa1. Thus, these results make these micelles a promising nanomedicine formulation for selective therapy.

PEG-PCL-based nanomedicines: A biodegradable drug delivery system and its application

The lack of efficient therapeutic options for many severe disorders including cancer spurs demand for improved drug delivery technologies. Nanoscale drug delivery systems based on poly(ethylene glycol)-poly(ε-caprolactone) copolymers (PEG-PCL) represent a strategy to implement therapies with enhanced drug accumulation at the site of action and decreased off-target effects. In this review, we discuss state-of-the-art nanomedicines based on PEG-PCL that have been investigated in a preclinical setting. We summarize the various synthesis routes and different preparation methods used for the production of PEG-PCL nanoparticles. Additionally, we review physico-chemical properties including biodegradability, biocompatibility, and drug loading. Finally, we highlight recent therapeutic applications investigated in vitro and in vivo using advanced systems such as triggered release, multi-component therapies, theranostics, or gene delivery systems.

Nanocarriers protecting toward an intestinal pre-uptake metabolism

Pre-uptake metabolism within the GI tract is responsible for the poor oral bioavailability of numerous drugs. As nanocarriers function as a 'shield', protecting incorporated drugs from enzymatic attack, there is an increasing interest in utilizing them as a tool for overcoming drug degradation. Degradation of carriers resulting in the release of incorporated drugs, mucus permeation, enzyme inhibitory properties and their toxicity are crucial factors that must be taken into account when designing proper nanocarriers. The use of polymer- and lipid-based nanocarriers as protective vehicles are discussed within this review. Lipid-based carriers and novel mucopenetrating particles seem to have a great potential in avoiding metabolizing enzymes. Accordingly, nanocarriers are promising tools for improving the bioavailability of drugs, being sensitive to a pre-uptake metabolism.

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.

Reflectometric interference spectroscopy-based sensing for evaluating biodegradability of polymeric thin films

Enzymatic degradation of poly(ε-caprolactone) (PCL) thin films was analyzed by reflectometric interference spectroscopy (RIfS)-based sensing system, and validated by attenuated total reflection infrared spectroscopy (ATR-IR) imaging. The degradation of the PCL thin film spin-coated on the silicon substrate on which 65-nm silicon nitride layer was deposited as an interference layer was easily monitored by shifting the peak bottom of reflectance spectra (Δλ) that is known to be proportional to the thickness of thin films. The Δλ values decreased with increasing the concentration of lipase from Pseudomonas cepacia, and the obtained sensorgrams were applied for kinetic analysis using a curve fitting software. ATR-IR spectra and imaging analysis on the surface of the PCL film revealed that carbonyl groups on the surface decreased with time, resulting from proceeding with the enzymatic hydrolysis, and importantly, extinction of the carbonyl group was declined with proportional to the decrease in the film thickness measured by the RIfS system. Consequently, the present RIfS-based label-free monitoring system can provide a simple and reliable way for evaluating biodegradability on synthetic materials.

STATEMENT OF SIGNIFICANCE

A RIfS-based sensing system in combination with ATR-IR measurements can be an analytical method for evaluation of biodegradability of polymeric thin films. This study demonstrates the utility of the RIfS-based sensing approach for analyzing the lipase-catalyzed degradation of PCL. Despite the RIfS is known as an inexpensive label-free detection method for biological interaction, the RIfS applications as monitoring methods for enzymatic degradation of biodegradable polymers had not been systematically explored. This study additionally demonstrated the capability of combined analysis of the biodegradation with ATR-IR spectra/imaging and RIfS measurements, which could be broadly applied towards evaluating biodegradability of various biodegradable polymers in environmental protection research.

A hollow porous magnetic nanocarrier for efficient near-infrared light- and pH-controlled drug release

A NIR light and pH dual responsive nanocarrier was fabricated for anti-cancer drug delivery as well as MRI and fluorescence cell imaging.

Bioresorbable polymersomes for targeted delivery of cisplatin

Nontoxic bioresorbable polymersomes have been developed that efficiently and site-selectively tether targeting peptides under mild conditions with no toxic catalysts. The binding and release properties of these polymersomes have been evaluated when targeting DLD-1 human colon cancer cells overexpressing the α(5)β(1) integrin. The delivery efficacy to these cells is markedly improved over commonly used RGD targeting peptides by use of an α(5)β(1)-specific targeting peptide, PR_b. Release profiles in buffered solution from pH 7.4 to 4.5 were evaluated and compared to release after binding to cells, and enzymatic degradation was identified as a major cause of rapid payload release in the cell. Intracellular trafficking and release were imaged via confocal microscopy in live cells and colocalization with organelles was evaluated quantitatively over time. Finally, the anticancer drug cisplatin was encapsulated in the PR_b functionalized polymersomes and the presence of PR_b greatly improved delivery efficacy, with increased cisplatin-induced losses to targeted DLD-1 colon cancer cell viability. When delivered to CACO-2 model human epithelial cells expressing low levels of α(5)β(1) integrin, low toxicity was maintained, suggesting that targeting was specific to α(5)β(1) overexpressing cells. These results demonstrate that PR_b-functionalized bioresorbable polymersomes may be an attractive route to minimizing the dose-limiting side effects associated with existing approaches to cisplatin chemotherapy.

Modulating rheological and degradation properties of temperature-responsive gelling systems composed of blends of PCLA-PEG-PCLA triblock copolymers and their fully hexanoyl-capped derivatives

In this study, the ability to modulate rheological and degradation properties of temperature-responsive gelling systems composed of aqueous blends of poly(ε-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-lactide) (PCLA-PEG-PCLA) triblock copolymers (i.e. uncapped) and their fully capped derivatives was investigated. Uncapped and capped PCLA-PEG-PCLA triblock copolymers, abbreviated as degree of modification 0 and 2 (DM0 and DM2, respectively), were composed of identical PCLA and PEG blocks but different end groups: namely hydroxyl and hexanoyl end groups. DM0 was synthesized by ring opening polymerization of l-lactide and ε-caprolactone in toluene using PEG as initiator and tin(II) 2-ethylhexanoate as the catalyst. A portion of DM0 was subsequently reacted with an excess of hexanoyl chloride in solution to yield DM2. The cloud point and phase behaviour of DM0 and DM2 in buffer as well as that of their blends were determined by light scattering in a diluted state and by vial tilting and rheological measurements in a concentrated state. Degradation/dissolution properties of temperature-responsive gelling systems were studied in vitro at pH 7.4 and 37°C. The cloud points of DM0/DM2 blends were ratio-dependent and could be tailored from 15 to 40°C for blends containing 15 to 100wt.% DM0. Vial tilting and rheological experiments showed that, with solid contents between 20 and 30wt.%, DM0/DM2 blends (15/85 to 25/75w/w) had a sol-to-gel transition temperature at 10-20°C, whereas blends with less than 15wt.% DM0 formed gels below 4°C and the ones with more than 25wt.% DM0 did not show a sol-to-gel transition up to 50°C. Complete degradation of temperature-responsive gelling systems took ∼100days, independent of the DM0 fraction and the initial solid content. Analysis of residual gels in time by GPC and (1)H-NMR showed no chemical polymer degradation, but indicated gel degradation by dissolution. Preferential dissolution of lactoyl-rich polymers induced enrichment of the residual gels in caproyl-rich polymers. To the best of our knowledge, degradation of temperature-responsive gelling systems by dissolution has not been reported or hypothesized as being the consequence of acylation of polymers. In conclusion, blending of PCLA-PEG-PCLA triblock polymers composed of identical backbones but different end groups provides for a straightforward preparation of temperature-responsive gelling systems with well-characterized rheological properties and potential in drug delivery. Furthermore, acylation of triblock copolymers may allow for the design of bioerodible systems with control over degradation by polymer dissolution.

Micellar nanocarriers assembled from doxorubicin-conjugated amphiphilic macromolecules (DOX-AM)

Amphiphilic macromolecules (AMs) have unique branched hydrophobic domains attached to linear PEG chains. AMs self-assemble in aqueous solution to form micelles that are hydrolytically stable in physiological conditions (37 degrees C, pH 7.4) over 4 weeks. Evidence of AM biodegradability was demonstrated by complete AM degradation after 6 d in the presence of lipase. Doxorubicin (DOX) was chemically conjugated to AMs via a hydrazone linker to form DOX-AM conjugates that self-assembled into micelles in aqueous solution. The conjugates were compared with DOX-loaded AM micelles (i.e., physically loaded DOX) on DOX content, micellar sizes and in vitro cytotoxicity. Physically encapsulated DOX loading was higher (12 wt.-%) than chemically bound DOX (6 wt.-%), and micellar sizes of DOX-loaded AMs (approximately 16 nm) were smaller than DOX-AMs (approximately 30 nm). In vitro DOX release from DOX-AM conjugates was faster at pH 5.0 (100%) compared to pH 7.4 (78%) after 48 h, 37 degrees C. Compared to free DOX and physically encapsulated DOX, chemically bound DOX had significantly higher cytotoxicity at 10(-7) M DOX dose against human hepatocellular carcinoma cells after 72 h. Overall, DOX-AM micelles showed promising characteristics as stable, biodegradable DOX nanocarriers.

Overcoming the barriers in micellar drug delivery: loading efficiency, in vivo stability, and micelle-cell interaction

IMPORTANCE OF THE FIELD

Spontaneously constructed from block copolymers in aqueous media, the polymer micelle has been extensively studied as a potential carrier of poorly water-soluble drugs, but cellular uptake pathways and stability of micelles in blood have not yet been clearly understood. An in-depth insight into the physical and biological behaviors of polymer micelles is necessitated for designing next-generation micelles.

AREAS COVERED IN THIS REVIEW

This review suggests possible solutions to improve micellar drug loading capacity, scrutinizes the parameters influencing the micelle stability in blood, and also discusses the fate of micelles in cellular and in vivo environment, respectively. Direct and indirect evidences from the literatures mostly published after 90's were collected, analyzed and summarized.

WHAT THE READER WILL GAIN

A critical analysis of micelle's stability in vivo and micelle-cell interaction is provided to highlight the key issues to be addressed to affirm that micelle can properly work as a drug carrier in clinical settings.

TAKE HOME MESSAGE

With a clear understanding of its behaviors in biological environment, the polymer micelle is a promising nanocarrier for chemotherapy.

A review of analytical methods for the identification and characterization of nano delivery systems in food

Detection and characterization of nano delivery systems is an essential part of understanding the benefits as well as the potential toxicity of these systems in food. This review gives a detailed description of food nano delivery systems based on lipids, proteins, and/or polysaccharides and investigates the current analytical techniques that can be used for the identification and characterization of these delivery systems in food products. The analytical approaches have been subdivided into three groups; separation techniques, imaging techniques, and characterization techniques. The principles of the techniques together with their advantages and drawbacks, and reported applications concerning nano delivery systems, or otherwise related compounds are discussed. The review shows that for a sufficient characterization, the nano delivery systems need to be separated from the food matrix, for which high-performance liquid chromatography or field flow fractionation are the most promising techniques. Subsequently, online photon correlation spectroscopy and mass spectrometry seem to be a convenient combination of techniques to characterize a wide variety of nano delivery systems.

Photocytotoxicity of mTHPC (temoporfin) loaded polymeric micelles mediated by lipase catalyzed degradation

PURPOSE

To study the in vitro photocytotoxicity and cellular uptake of biodegradable polymeric micelles loaded with the photosensitizer mTHPC, including the effect of lipase-catalyzed micelle degradation.

METHODS

Micelles of mPEG750-b-oligo(epsilon-caprolactone)5 (mPEG750-b-OCL5) with a hydroxyl (OH), benzoyl (Bz) or naphthoyl (Np) end group were formed and loaded with mTHPC by the film hydration method. The cellular uptake of the loaded micelles, and their photocytotoxicity on human neck squamous carcinoma cells in the absence and presence of lipase were compared with free and liposomal mTHPC (Fospeg).

RESULTS

Micelles composed of mPEG750-b-OCL5 with benzoyl and naphtoyl end groups had the highest loading capacity up to 30% (w/w), likely due to pi-pi interactions between the aromatic end group and the photosensitizer. MTHPC-loaded benzoylated micelles (0.5 mg/mL polymer) did not display photocytotoxicity or any mTHPC-uptake by the cells, in contrast to free and liposomal mTHPC. After dilution of the micelles below the critical aggregation concentration (CAC), or after micelle degradation by lipase, photocytotoxicity and cellular uptake of mTHPC were restored.

CONCLUSION

The high loading capacity of the micelles, the high stability of mTHPC-loaded micelles above the CAC, and the lipase-induced release of the photosensitizer makes these micelles very promising carriers for photodynamic therapy in vivo.