Tunable Degradation Behavior of PEGylated Polyester-Based Nanoparticles Obtained Through Emulsion Free Radical Polymerization

Glycerol- and diglycerol-based polyesters: Evaluation of backbone alterations upon nano-formulation performance

Despite the success of polyethylene glycol-based (PEGylated) polyesters in the drug delivery and biomedical fields, concerns have arisen regarding PEG's immunogenicity and limited biodegradability. In addition, inherent limitations, including limited chemical handles as well as highly hydrophobic nature, can restrict their effectiveness in physiological conditions of the polyester counterpart. To address these matters, an increasing amount of research has been focused towards identifying alternatives to PEG. One promising strategy involves the use of bio-derived polyols, such as glycerol. In particular, glycerol is a hydrophilic, non-toxic, untapped waste resource and as other polyols, can be incorporated into polyesters via enzymatic catalysis routes. In the present study, a systematic screening is conducted focusing on the incorporation of 1,6-hexanediol (Hex) (hydrophobic diol) into both poly(glycerol adipate) (PGA) and poly(diglycerol adipate) (PDGA) at different (di)glycerol:hex ratios (30:70; 50:50 and 70:30 mol/mol) and its effect on purification upon NPs formation. By varying the amphiphilicity of the backbone, we demonstrated that minor adjustments influence the NPs formation, NPs stability, drug encapsulation, and degradation of these polymers, despite the high chemical similarity. Moreover, the best performing materials have shown good biocompatibility in both in vitro and in vivo (whole organism) tests. As preliminary result, the sample containing diglycerol and Hex in a 70:30 ratio, named as PDGA-Hex 30%, has shown to be the most promising candidate in this small library analysed. It demonstrated comparable stability to the glycerol-based samples in various media but exhibited superior encapsulation efficiency of a model hydrophobic dye. This in-depth investigation provides new insights into the design and modification of biodegradable (di)glycerol-based polyesters, potentially paving the way for more effective and sustainable PEG-free drug delivery nano-systems in the pharmaceutical and biomedical fields.

Nanostructured Poly-l-lactide and Polyglycerol Adipate Carriers for the Encapsulation of Usnic Acid: A Promising Approach for Hepatoprotection

The present study investigates the utilization of nanoparticles based on poly-l-lactide (PLLA) and polyglycerol adipate (PGA), alone and blended, for the encapsulation of usnic acid (UA), a potent natural compound with various therapeutic properties including antimicrobial and anticancer activities. The development of these carriers offers an innovative approach to overcome the challenges associated with usnic acid's limited aqueous solubility, bioavailability, and hepatotoxicity. The nanosystems were characterized according to their physicochemical properties (among others, size, zeta potential, thermal properties), apparent aqueous solubility, and in vitro cytotoxicity. Interestingly, the nanocarrier obtained with the PLLA-PGA 50/50 weight ratio blend showed both the lowest size and the highest UA apparent solubility as well as the ability to decrease UA cytotoxicity towards human hepatocytes (HepG2 cells). This research opens new avenues for the effective utilization of these highly degradable and biocompatible PLLA-PGA blends as nanocarriers for reducing the cytotoxicity of usnic acid.

Estimating the bioaccessibility of flocculants in the presence of sediments in model wastewater

The cationic degradable polymer poly(lactic acid) choline iodide ester methacrylate, poly(PLA₄ChMA), can be used to flocculate particles and dewater sediments from tailings ponds and wastewater. A suitable bioaccessibility method is required to characterize the interactions of this novel flocculant in the human gastrointestinal system. To this end, a physiologically based extraction test (PBET) was modified to evaluate the bioaccessibility of flocculants. Bioaccessibility (bioaccessible fraction) is a measure of the solubility of a contaminant in gastrointestinal fluids and that may be available for systemic absorption. The flocculants poly(PLA₄ChMA), SNF C3276, and FLOPAM A3338 were tested at a solid-to-liquid ratio of 1:200 in the absence and presence of kaolin clay, which is used as a model sediment compound. Bioaccessible fractions were characterized by proton nuclear magnetic resonance spectroscopy and estimated by gravimetry. The bioaccessibility of poly(PLA₄ChMA) in gastric and intestinal PBET solutions decreases from 78% to 100%, respectively, in the absence of kaolin to approximately 0% with kaolin, indicating that poly(PLA₄ChMA) remains adsorbed onto the clay surface throughout the PBET, a result confirmed by thermogravimetric analysis. The bioaccessibility of cationic SNF C3276 and anionic FLOPAM A3338 in gastric solution is approximately 76% and 26%, respectively, and is not affected by the presence of kaolin. However, in intestinal solutions, the bioaccessibility of SNF C3276 and FLOPAM A3338 (60-85% in the absence of kaolin) changes to 0% and 100%, respectively, in the presence of kaolin. These results, interpreted in terms of solution pH and surface charge, demonstrate that interactions with kaolin influence the solubility of flocculants and must be considered in the evaluation of bioaccessibility. In future works, such bioaccessibility methods can be applied to assess the human-health safety of using flocculants in wastewater treatments.

Miniemulsion polymerization at low temperature: A strategy for one-pot encapsulation of hydrophobic anti-inflammatory drugs into polyester-containing nanoparticles

HYPOTHESIS

Conventional synthesis methods of polymeric nanoparticles as drug delivery systems are based on the use of large amounts of organic solvents, hence requiring several steps for the obtaining of waterborne dispersions. In view of the need for new environmentally friendly methods, emulsion polymerization and their related techniques are a good alternative for the production of monodispersed waterborne dispersions of biodegradable nanoparticles in a cleaner, reproducible and faster manner.

EXPERIMENTS

Herein, the miniemulsion polymerization technique at low temperature using poly(2-ethyl-2-oxazoline) as surfactant has been developed for poly(hydroxyethyl methacrylate-lactic acid) and poly(hydroxyethyl methacrylate-lactic-co-glycolic acid) nanoparticles. Additionally, the anti-inflammatory drug BRP-187 was used to proof the potential of this technique in the encapsulation of hydrophobic drugs. The effect of the oligomer composition on the miniemulsion and the final dispersion stability, the final oligomer conversion, the polymer particle size and the drug encapsulation efficiency has been studied.

FINDINGS

Monodisperse spherical particles ranging between 170 and 250 nm in diameter in long term non-toxic stable waterborne dispersions were obtained with drug encapsulation efficiencies up to 66%. In contrast with conventional synthesis techniques, residual organic solvents are completely removed and, thus, the potential of redox initiated miniemulsion polymerization to obtain stable drug loaded poly(hydroxyethyl methacrylate-lactic acid) and poly(hydroxyethyl methacrylate-lactic-co-glycolic acid) nanoparticles in an efficient and fast manner is shown.

Sequentially bridging anionic addition and ring-opening polymerization by cooperative organocatalysis: Well-defined block copolymers from methacrylates and cyclic esters

Organocatalytic sequential block copolymerization of dissimilar monomers with distinct chemical characteristics is great challenging, usually involving the integration of different polymerization mechanism. In this contribution, we reported the synthesis of...

Evaluation of a Novel Polymeric Flocculant for Enhanced Water Recovery of Mature Fine Tailings

The novel cationic flocculant, poly(lactic acid) choline iodide ester methacrylate (poly(PLA4ChMA)), has been shown to provide improved flocculation of 5.0 wt.% mature fine tailings (MFT) diluted in deionized water compared to commercial anionic polymers, with continued dewatering of the sediment occurring as the polymer undergoes partial hydrolytic degradation. However, the elevated dosages (10,000 ppm) required would make the polymer costly to implement on an industrial scale. With this motivation, the impact of MFT loading and the use of process water is explored while comparing the settling performance of poly(PLA4ChMA) to available commercial alternatives such as anionic FLOPAM A3338. Improved consolidation of 5.0 wt.% MFT diluted with process water could be achieved at reduced dosages (500 ppm) with poly(PLA4ChMA). However, the final compaction levels after polymer degradation were similar to those achieved with the nondegradable commercial flocculants. Flocculation-filtration experiments with undiluted MFT are also conducted to compare the performance of the polymers. Significantly faster rates of water release were observed with the cationic flocculants compared to FLOPAM A3338, but no improvement in the overall tailings compaction was found either before or after poly(PLA4ChMA) degradation. Thus, the improved dewatering observed with poly(PLA4ChMA) in dilute MFT suspensions does not extend to conditions that would be encountered in the field.

Surfactant-free and rinsing-resistant biodegradable nanoparticles with high adsorption on natural fibers for the long-lasting release of fragrances

Synthetic polymers are attracting growing attention as additives for laundry and personal care products. In particular, the high volatility of many common fragrances requires the development of polymeric particles for their encapsulation and controlled release. Unfortunately, the vast majority of these carriers is made from polymers that are not biodegradable. This poses severe concerns about the accumulation of nano- and microplastics. Hence, such particles are expected to be banned from the market in the coming years. Therefore, biodegradable particles enabling a long-lasting release of the fragrances are urgently needed. In this work, we produced biodegradable nanoparticles (NPs) that are structurally composed of lactones, i.e. well known perfumes that occur naturally and that are already considered safe by regulatory agencies. We polymerized these lactones via ring opening polymerization (ROP) using an ionizable tertiary amine as initiator to produce in a single step amphiphilic oligoesters able to directly self-assemble into NPs once nanoprecipitated in water. In this way, we can produce biodegradable NPs with a perfume loading up to 85 % w/w without the need for additional surfactants. Subsequently we show that the ionizable group is able to confer a positive charge to our nanoparticles and, in turn, a high adsorption capacity on natural fibers (i.e. hairs and cotton fabric). Finally, we demonstrate the nanoparticle resistance to rinsing and their ability to confer a long-lasting fragrance perception to treated hair swatches for at least 3 weeks.

Starch/Poly (Glycerol-Adipate) Nanocomposite Film as Novel Biocompatible Materials

Starch is one of the most abundant polysaccharides on the earth and it is the most important source of energy intake for humans. Thermoplastic starch (TPS) is also widely used for new bio-based materials. The blending of starch with other molecules may lead to new interesting biodegradable scaffolds to be exploited in food, medical, and pharmaceutical fields. In this work, we used native starch films as biopolymeric matrix carriers of chemo enzymatically-synthesized poly (glycerol-adipate) (PGA) nanoparticles (NPs) to produce a novel and biocompatible material. The prototype films had a crystallinity ranging from 4% to 7%. The intrinsic and thermo-mechanical properties of the composite showed that the incorporation of NPs in the starch films decreases the glass transition temperature. The utilization of these film prototypes as the basis for new biocompatible material showed promise, particularly because they have a very low or even zero cytotoxicity. Coumarin was used to monitor the distribution of the PGA NPs in the films and demonstrated a possible interaction between the two polymers. These novel hybrid nanocomposite films show great promise and could be used in the future as biodegradable and biocompatible platforms for the controlled release of amphiphilic and hydrophobic active ingredients.

Exploring the enzymatic degradation of poly(glycerol adipate)

Poly(glycerol adipate) (PGA) is a biodegradable, biocompatible, polymer with a great deal of potential in the field of drug delivery. Active drug molecules can be conjugated to the polymer backbone or encapsulated in self-assembled nanoparticles for targeted and systemic delivery. Here, a range of techniques have been used to characterise the enzymatic degradation of PGA extensively for the first time and to provide an indication of the way the polymer will behave and release drug payloads in vivo. Dynamic Light Scattering was used to monitor change in nanoparticle size, indicative of degradation. The release of a fluorescent dye, coupled to PGA, upon incubation with enzymes was measured over a 96 h period as a model of drug release from polymer drug conjugates. The changes to the chemical structure and molecular weight of PGA following enzyme exposure were characterised using FTIR, NMR and GPC. These techniques provided evidence of the biodegradability of PGA, its susceptibility to degradation by a range of enzymes commonly found in the human body and the polymer's potential as a drug delivery platform.

Hydrazone linked doxorubicin-PLA prodrug nanoparticles with high drug loading

An optimal drug delivery system should be characterized by biocompatibility, biodegradability, high drug loading and favorable drug release profile. To achieve this goal a hydrazone linked doxorubicin-poly(lactic acid) prodrug (PLA-DOX) was synthesized by the functionalization of a short polymer chain produced by ring opening polymerization. The hydrophobic prodrug generated in this way was nanoprecipitated using a block copolymer to form polymeric nanoparticles (NPs) with a quantitative loading efficiency and a high and tunable drug loading. The effects of the concentration of the PLA-DOX prodrug and surfactant were studied by dynamic light scattering showing a range of NP size between 50 and 90 nm and monodispersed size distributions with polydispersity indexes lower then 0.27 up to a maximum DOX concentration of 27% w/w. The release profile of DOX from these NPs, tested at different pH conditions, showed a higher release rate in acidic conditions, consistent with the nature of the hydrazone bond which was used to conjugate the drug to the polymer. In vitro cytotoxicity studies performed on BV2 microglia-like cell line highlighted a specific cytotoxic effect of these NPs suggesting the maintenance of the drug efficacy and a modified release profile upon encapsulation of DOX in the NPs.

Zwitterionic Polyester-Based Nanoparticles with Tunable Size, Polymer Molecular Weight, and Degradation Time

Biodegradable polymer nanoparticles are an important class of materials used in several applications for their unique characteristics. In particular, the ones stabilized by zwitterionic materials are gaining increased interest in medicine as alternative to the more common ones based on poly(ethylene glycol) thanks to their superior stability and ability to avoid both the accelerated blood clearance and allergic reactions. In this work, a novel class of zwitterionic based NPs has been produced, and a method to independently control the nanoparticle size, degradation time, and polymer molecular weight has been developed and demonstrated. This has been possible by the synthesis and the fine-tuning of zwitterionic amphiphilic block copolymers obtained via the combination of ring-opening polymerization and reversible addition-fragmentation chain transfer polymerization. The final results showed that when two block copolymers contain the same number of caprolactone units, the one with longer oligoester lateral chains degrades faster. This phenomenon is in sharp contrast with the one seen so far for the common linear polyester systems where longer chains result in longer degradation times, and it can be used to better tailor the degradation behavior of the nanoparticles.

Strategies to combine ROP with ATRP or RAFT polymerization for the synthesis of biodegradable polymeric nanoparticles for biomedical applications

The available strategies to combine CRPs and ROP in the synthesis of highly engineered polymer nanoparticles are here critically discussed.

Dewatering Oil Sands Tailings with Degradable Polymer Flocculants

We synthesized hydrolytically degradable cationic polymers by micellar radical polymerization of a short-chain polyester macromonomer, polycaprolactone choline iodide ester methacrylate (PCL₂ChMA) with two polyester units, and used them to flocculate oil sands mature fine tailings (MFT). We evaluated the flocculation performance of the homopolymer and copolymers with 30 mol % acrylamide (AM) by measuring initial settling rate (ISR), supernatant turbidity, and capillary suction time (CST) of the sediments. Flocculants made with trimethylaminoethyl methacrylate chloride (TMAEMC), the monomer corresponding to PCL_nChMA with n = 0, have improved performance over poly(PCL₂ChMA) at equivalent loadings due to their higher charge density per gram of polymer. However, MFT sediments flocculated using the PCL₂ChMA-based polymers are easier to dewater (up to an 85% reduction in CST) after accelerated hydrolytic degradation of the polyester side chains. This study demonstrates the potential of designing cationic polymers that effectively flocculate oil sands tailings ponds, and also further dewater the resulting solids through polymer degradation.

Synthesis and Nanoprecipitation of HEMA-CLn Based Polymers for the Production of Biodegradable Nanoparticles

The control over the size distribution and stability of polymeric nanoparticles (NPs) is crucial in many of their applications, especially in the biomedical field. These characteristics are typically influenced by the production method and the nature of the starting material. To investigate these aspects, the controlled radical polymerization of functionalized methacrylates constituted by 2-hydroxyethyl methacrylate (HEMA) functionalized with a controlled number of ε-caprolactone (CL) units (HEMA-CL_n), was carried out via reversible addition–fragmentation chain transfer polymerization (RAFT) in solution. The living reaction allows for good control over the molar mass of the final polymer with a low molar mass dispersity. The obtained polymer solutions were nanoprecipitated in order to produce NPs suitable for drug delivery applications with narrow particle size distribution and a wide size range (from 60 to 250 nm). The NP synthesis has been performed using a mixing device, in order to control the parameters involved in the nanoprecipitation process. As already seen for similar systems, the size of the produced NPs is a function of the polymer concentration during the nanoprecipitation process. Nevertheless, when the polymer concentration is kept constant, the NP size is influenced by the chemical structure of the polymer used, in terms of the presence of PEG (poly(ethylene glycol)), the degree of RAFT polymerization, and the length of the caprolactone side chain. These characteristics were also found to influence the stability and degradation properties of the produced NPs.

Polymer Nanoparticle Engineering for Podocyte Repair: From in Vitro Models to New Nanotherapeutics in Kidney Diseases

Specific therapeutic targeting of kidney podocytes, the highly differentiated ramified glomerular cells involved in the onset and/or progression of proteinuric diseases, could become the optimal strategy for preventing chronic kidney disease. With this aim, we developed a library of engineered polymeric nanoparticles (NPs) of tuneable size and surface properties and evaluated their interaction with podocytes. NP cytotoxicity, uptake, and cytoskeletal effects on podocytes were first assessed. On the basis of these data, nanodelivery of dexamethasone loaded into selected biocompatible NPs was successful in repairing damaged podocytes. Finally, a three-dimensional in vitro system of co-culture of endothelial cells and podocytes was exploited as a new tool for mimicking the mechanisms of NP interaction with glomerular cells and the repair of the kidney filtration barrier.

Polylactic acid macromonomer radical propagation kinetics and degradation behaviour

Polylactic acid (PLA) macromonomer radical homopropagation rate coefficients are evaluated as a function of average macromonomer chain length. Hydrolysis studies of nanoparticles (NP) produced from PLA macromonomers demonstrate the importance of end-group functionality on NP degradation time.

Poly(HPMA)-based copolymers with biodegradable side chains able to self assemble into nanoparticles

Biocompatible PCL-based nanoparticles able to degrade into completely water soluble poly(HPMA) chains are produced via the inverse macromonomer method.

Small interfering RNA delivery through positively charged polymer nanoparticles

Small interfering RNA (siRNA) is receiving increasing attention with regard to the treatment of many genetic diseases, both acquired and hereditary, such as cancer and diabetes. Being a high molecular weight (MW) polyanion, siRNA is not able to cross a cell membrane, and in addition it is unstable in physiological conditions. Accordingly, a biocompatible nanocarrier able to deliver siRNA into cells is needed. In this work, we synthesized biocompatible positively charged nanoparticles (NPs) following a two-step process that involves ring opening polymerization (ROP) and emulsion free radical polymerization (EFRP). Firstly, we proved the possibility of fine tuning the NPs' characteristics (e.g. size and surface charge) by changing the synthetic process parameters. Then the capability in loading and delivering undamaged siRNA into a cancer cell cytoplasm has been shown. This latter process occurs through the biodegradation of the polymer constituting the NPs, whose kinetics can be tuned by adjusting the polymer's MW. Finally, the ability of NPs to carry siRNA inside the cells in order to inhibit their target gene has been demonstrated using green flourescent protein positive cells.

New N-acyl amino acid-functionalized biodegradable polyesters for pharmaceutical and biomedical applications

Aminoacyl PGA: a biodegradable polyester modified with amino acids to provide a range of physicochemical characteristics for interaction with drugs.

Multiple strategies to produce lipophilic nanoparticles leaving water-soluble poly(HPMA)

N-(2-Hydroxypropyl) methacrylamide (HPMA) is used to produce water-soluble polymers with non-immumogenic properties that can be used in drug delivery applications.