Influence of pH on the kinetics of polymer hydrolysis: The case of polylactic acid

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Selectively Fluorinated PAMAM-Arginine Conjugates as Gene Delivery Vectors

: Polyamidoamine (PAMAM) dendrimers are among the most studied cationic polymers as non-viral gene delivery vectors. However, an "ideal" PAMAM-based gene delivery vector is still missing due to the high manufacturing costs and non-negligible cytotoxicity associated with the use of high-generation dendrimers, whereas low-generation dendrimers are far from displaying efficient gene transfection. In order to cover this gap in the literature, in this study, we propose the functionalization of the outer primary amines of PAMAM G2 and PAMAM G4 with building blocks bearing fluorinated moieties along with a guanidino functional group. We have designed and synthetized two fluorinated arginine (Arg)-based Michael acceptors which were straightforwardly "clicked" to PAMAM dendrimers without the need for coupling reagents and/or catalysts. The obtained conjugates, in particular, derivative 1 formed starting from the low-cost PAMAM G2 and a building block bearing two trifluoromethyl groups, were able to efficiently complex plasmid DNA, had negligible cytotoxicity, and showed improved gene transfection efficiency as compared to undecorated PAMAM dendrimers and a corresponding unfluorinated PAMAM-Arg derivative, with derivative 1 being two orders of magnitude more efficient than the gold standard branched polyethylenimine, bPEI, 25 kDa. These results highlight the importance of the presence of trifluoromethyl moieties for both gene transfection and a possible future application in 19F magnetic resonance imaging

Role of the Polymer Microstructure in Controlling Colloidal and Thermo-Responsive Properties of Nano-Objects Prepared Via RAFT Polymerization in a Non-polar Medium

After having demonstrated their potential in biomedicalapplications,thermo-responsive block copolymers that are able to self-assembleinto nano-objects in response to temperature modifications are becomingmore and more appealing in other sectors, such as the oil and gasand lubricant fields. Reversible addition-fragmentation chaintransfer (RAFT) polymerization-induced self-assembly has been demonstratedas a valuable strategy for producing nano-objects from modular blockcopolymers in non-polar media, required for the mentioned applications.Although the influence of the nature and size of the thermo-responsiveblock of these copolymers on the properties of the nano-objects isextensively studied in the literature, the role of the solvophilicblock is often neglected. In this work, we elucidate the role of themain microstructural parameters, including those of the solvophilicportion, of block copolymers produced by RAFT polymerization in thehydrocarbon blend decane/toluene 50:50 v/v on the thermo-responsivebehavior and colloidal properties of the resulting nano-objects. Twolong-aliphatic chain monomers were employed for the synthesis of fourmacromolecular chain transfer agents (macroCTAs), with increasingsolvophilicity according to the number of units (n) or length of the alkyl side chain (q). Subsequently,the macroCTAs were chain-extended with different repeating units ofdi(ethylene glycol) methyl ether methacrylate (p),leading to copolymers that are able to self-assemble below a criticaltemperature. We show that this cloud point can be tuned by actingon n, p, and q.On the other hand, the colloidal stability, expressed in terms ofarea of the particle covered by each solvophilic segment, is onlya function of n and q, which providesa way for controlling the size distribution of the nano-objects andto decouple it from the cloud point

Soft sensor based on Raman spectroscopy for the in-line monitoring of metabolites and polymer quality in the biomanufacturing of polyhydroxyalkanoates

Polyhydroxyalkanoates (PHA) are among the most promising bio-based alternatives to conventional petroleum-based plastics. These biodegradable polyesters can in fact be produced by fermentation from bacteria like Cupriavidus necator, thus reducing the environmental footprint of the manufacturing process. However, ensuring consistent product quality attributes is a major challenge of biomanufacturing. To address this issue, the implementation of real-time monitoring tools is essential to increase process understanding, enable a prompt response to possible process deviations and realize on-line process optimization. In this work, a soft sensor based on in situ Raman spectroscopy was developed and applied to the in-line monitoring of PHA biomanufacturing. This strategy allows the collection of quantitative information directly from the culture broth, without the need for sampling, and at high frequency. In fact, through an optimized multivariate data analysis pipeline, this soft sensor allows monitoring cell dry weight, as well as carbon and nitrogen source concentrations with root mean squared errors (RMSE) equal to 3.71, 7 and 0.03 g/L, respectively. In addition, this tool allows the in-line monitoring of intracellular PHA accumulation, with an RMSE of 14 gPHA/gCells. For the first time, also the number and weight average molecular weights of the polymer produced could be monitored, with RMSE of 8.7E4 and 11.6E4 g/mol, respectively. Overall, this work demonstrates the potential of Raman spectroscopy in the in -line monitoring of biotechnology processes, leading to the simultaneous measurement of several process variables in real time without the need of sampling and labor-intensive sample preparations

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

Poly(N-(2-Hydroxypropyl) methacrylamide) (poly(HPMA)) is gaining pharmaceutical attention in replacement to PEG as a hydrophilic stabilizer for polymer nanoparticles (NPs) devoted to systemic administration.[1] This is due to its biocompatibility, prolonged circulation time and, compared to PEG, to the avoidance of allergic reactions and of the accelerated blood clearance effect.[2, 3] In this work, a lipophilic HPMA-based macromonomer with a predetermined and controllable structure is synthesized for the first time attaching a short oligo(caprolactone) chain obtained via Ring Opening Polymerization (ROP) to the HPMA using a succinic acid unit as a spacer. This biodegradable monomer (hereinafter HPMA-CL) was then used to synthesize well-defined amphiphilic block copolymers comprising a hydrophilic poly(HPMA) block and a hydrophobic poly(HPMA-CL) segment via Reversible Addition-Fragmentation Transfer (RAFT) polymerization. The combination of ROP and RAFT allows the production of a library of polymers with a predetermined and controlled structure that are able to self-assemble in water into biodegradable NPs with different size. In particular, such NPs are designed to degrade in aqueous environment into completely water soluble poly(HPMA), with a molecular weight that is below the critical threshold for the renal excretion. This is a very important feature since it allows to avoid polymer accumulation into the body once the NPs are injected.[4] The degradation time is a function of the number of caprolactone units in the HPMA-CL macromonomer and of its degree of polymerization in the NP forming copolymer. Then, the polymer structure can be adjusted to obtain the desired degradation time. Finally, the possibility for such nanoparticles to physically incorporate and mediate the release of a lipophilic antineoplastic drug was evaluated in the case of Trabectedin. The formulation proved to be biocompatible and to sustainedly release the drug for up to 24 hours. Please click Additional Files below to see the full abstract

Design of a twin-column countercurrent purification (MCSGP) unit for the polishing of an oligonucleotide sequence

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Process and cost modeling approaches for manufacturing operations utilizing multi- column chromatography applications

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Influence of pH on the kinetics of hydrolysis reactions: the case of epichlorohydrin and glycidol

Glycidol (GL) and epichlorohydrin (EPI) are two widely used molecules in chemical, pharmaceutical and food industry applications. However, their use in aqueous environments causes the formation of compounds, like monochloropropanediol (MCPD) and dichloropropanol (DCP), reported as dangerous for human health and therefore regulated by severe law restrictions. To identify the conditions leading to such species and design the corresponding processes in order to prevent their formation, hydrolysis and chlorination of EPI and GL, together with dehydrohalogenation of DCP and MCPD, have been systematically analysed. Different reaction conditions in terms of temperature, pH and chloride ion concentration have been experimentally investigated and the concentration of the involved species was tracked over time by gas chromatography and high-performance liquid chromatography. These experimental data were fitted through a kinetic model, which allowed a general expression of the observed rate constant of each reaction as a function of temperature and pH to be quantified. In particular, the reaction rates are conveniently expressed as combinations of three contributions: alkaline, neutral and acid. The corresponding rate laws explicitly account for the critical role of pH. The developed mechanistic model exhibits good prediction ability and may represent the basis for optimising processes employing EPI and GL

Enhanced flow synthesis of small molecules by in-line integration of sequential catalysis and benchtop twin-column continuous chromatography

We report an improved approach for the integration of flow synthesis and continuous chromatography, for applications in the end-to-end preparation of pharmaceutically-relevant small molecules. It involves the combination of sequential microreactors and twin-column counter-current chromatography based on the often-used C18 columns. The column loading method ensures that the product breaking through a fully loaded first column is loaded onto the second one, avoiding waste of precious material and technological complexity associated with the use of four-to-six columns typical of simulated moving bed chromatography. The system was applied to synthesize biphenyl via Suzuki–Miyaura reaction, and was also demonstrated for other structurally-different compounds. Compared to the discontinuous and other traditional approaches, our method leads to higher isolated yields (ca. +60%), higher productivity (ca. +30%), and reduced solvent consumption (ca. −80%). A circularity and life-cycle analysis was also conducted to demonstrate the environmental benefits of the flow process

From batch to continuous free-radical polymerization: Recent advances and hurdles along the industrial transfer

The care of safety and environment is nowadays an essential aspect in the conduction of every kind of factory. A decisive contribution to these aspects is given by the conversion from batch to continuous processes. In polymer manufacturing, this transition allows to better manage important safety and pollution concerns, such as energy transport phenomena and process emissions. This, in turn, facilitates the fulfilling of the more and more stringent requirements imposed by local and international regulatory agencies. In addition, through this process intensification, it is also possible to optimize both investment and operative costs, thus overcoming the current profit margin reduction in the field of polymerizations. The aim of this chapter is to provide an insight into the technical and process difficulties that are currently hampering the transition from batch to continuous free-radical polymerization (FRP). The discussion is driven by considering key points in polymer manufacturing, including safety, environmental concerns, product quality and cost management. For a seek of clarity, we drove the discussion by considering the two main modalities in which the FRP can be conducted, namely homogenous and heterogeneous reactions. Extensive reference to literature examples is made to highlight the state of art in the field and the recent innovations toward continuous processes. Finally, successful examples of such auspicable transition achieved on an industrial scale are presented, trying to highlight the features that can be generalized to reach the goal