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Thermostability is an important and desired feature of therapeutic proteins and is critical for the success or failure of protein drugs development. It can be increased by PEGylation-binding of poly(ethylene glycol) moieties-or glycosylation-post-translational modification to add glycans. Here, the thermostability and thermodynamic parameters of native, PEGylated, and glycosylated versions of the antileukemic enzyme crisantaspase were investigated. First-order kinetics was found to describe the irreversible deactivation process. Activation energy of the enzyme-catalyzed reaction (E*) was estimated for native, PEGylated, and glycosylated enzyme (10.2, 14.8, and 18.8 kJ mol-1 respectively). Half-life decreased progressively with increasing temperature, and longer half-life was observed for PEG-crisantaspase (87.74 min) at 50 °C compared to the native form (9.79 min). The activation energy of denaturation of PEG-crisantaspase (307.1 kJ mol-1) was higher than for crisantaspase (218.1 kJ mol-1) and Glyco-crisantaspase (120.0 kJ mol-1), which means that more energy is required to overcome the energy barrier of the unfolding process. According to our results, PEG-crisantaspase is more thermostable than its native form, while Glyco-crisantaspase is more thermosensitive.

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Chrysin is a natural flavonoid that despite having numerous biological properties, its therapeutic value is limited due to its very low solubility in aqueous media. In this work, chrysin was conjugated with methoxypolyethylene glycols (mPEGs) of different molecular weights (350, 500, 750, and 2000 g/mol), affording PEGylated chrysins with high yields and excellent purities. In all cases, an increase in the water solubility of the conjugates was observed, which was highest when 500 g/mol of mPEG was used in the PEGylation reaction. Furthermore, in aqueous solution, PEGylated chrysins formed aggregates of ellipsoid shape. Electrochemical studies showed that the redox properties were conserved after PEGylation. While in vitro antibacterial and antifungal studies probed that the intrinsic activity was conserved, in vitro antitumor activities against HepG2 (liver carcinoma cells) and PC3 (prostate cancer cell) showed that PEGylated chrysins retained the cytotoxic activity and the ability of induction of apoptosis for the evaluated human cancer cells.

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BACKGROUND: In a previous work, an IL-2Rßγ biased mutant derived from human IL-2 and called IL-2noα, was designed and developed. Greater antitumor effects and lower toxicity were observed compared to native IL-2. Nevertheless, mutein has some disadvantages, such as a very short half-life of about 9-12 min, propensity for aggregation, and solubility problems. OBJECTIVE: In this study, PEGylation was employed to improve the pharmacokinetic and antitumoral properties of the novel protein. METHODS: Pegylated IL-2noα was characterized by polyacrylamide gel electrophoresis, size exclusion chromatography, in vitro cell proliferation and in vivo cell expansion bioassays, and pharmacokinetic and antitumor studies. RESULTS: IL-2noα-conjugates with polyethylene glycol (PEG) of 1.2 kDa, 20 kDa, and 40 kDa were obtained by classical acylation. No significant changes in the secondary and tertiary structures of the modified protein were detected. A decrease in biological activity in vitro and a significant improvement in half-life were observed, especially for IL-2noα-PEG20K. PEGylation of IL-2noα with PEG20K did not affect the capacity of the mutant to induce preferential expansion of T effector cells over Treg cells. This pegylated IL-2noα exhibited a higher antimetastatic effect compared to unmodified IL-2noα in the B16F0 experimental metastases model, even when administered at lower doses and less frequently. CONCLUSION: PEG20K was selected as the best modification strategy, to improve the blood circulation time of the IL-2noα with a superior antimetastatic effect achieved with lower doses.

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A pioneering study regarding the isolation, biochemical evaluation, functional assays and first PEGylation report of a novel vascular endothelial growth factor from Crotalus durissus terrificus venom (CdtVEGF and PEG-CdtVEGF). CdtVEGF was isolated from crude venom using two different chromatographic steps, representing 2% of soluble venom proteins. Its primary sequence was determined using mass spectrometry analysis, and the molecule demonstrated no affinity to heparin. The Brazilian crotalid antivenom recognized CdtVEGF. Both native and PEGylated CdtVEGF were able to induce new vessel formation and migration, and to increase the metabolic activity of human umbilical endothelial vascular cells (HUVEC), resulting in better wound closure (~50% within 12 h) using the native form. CdtVEGF induced leukocyte recruitment to the peritoneal cavity in mice, with a predominance of neutrophil influx followed by lymphocytes, demonstrating the ability to activate the immune system. The molecule also induced a dose-dependent increase in vascular permeability, and PEG-CdtVEGF showed less in vivo inflammatory activity than CdtVEGF. By unraveling the intricate properties of minor components of snake venom like svVEGF, this study illuminates the indispensable significance of exploring these molecular tools to unveil physiological and pathological processes, elucidates the mechanisms of snakebite envenomings, and could possibly be used to design a therapeutic drug.

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The biological activity of antimicrobial peptides and proteins is closely related to their structural aspects and is sensitive to certain post-translational modifications such as glycosylation, lipidation and PEGylation. However, PEGylation of protein and peptide drugs has expanded in recent years due to the reduction of their toxicity. Due to their size, the PEGylation process can either preserve or compromise the overall structure of these biopolymers and their biological properties. The antimicrobial peptide LyeTx I-bcys was synthesized by Fmoc strategy and coupled to polyethylene glycol 2.0 kDa. The conjugates were purified by HPLC and characterized by MALDI-ToF-MS analysis. Microbiological assays with LyeTx I-bcys and LyeTx I-bPEG were performed against Staphylococcus aureus (ATCC 33591) and Escherichia coli (ATCC 25922) in liquid medium. MIC values of 2.0 and 1.0 µM for LyeTx I-bcys and 8.0 and 4.0 µM for LyeTx I-bPEG were observed against S. aureus and E. coli, respectively. PEGylation of LyeTx I-bcys (LyeTx I-bPEG) decreased the cytotoxicity determined by MTT method for VERO cells compared to the non-PEGylated peptide. In addition, structural and biophysical studies were performed to evaluate the effects of PEGylation on the nature of peptide-membrane interactions. Surface Plasmon Resonance experiments showed that LyeTx I-b binds to anionic membranes with an association constant twice higher than the PEGylated form. The three-dimensional NMR structures of LyeTx I-bcys and LyeTx I-bPEG were determined and compared with the LyeTx I-b structure, and the hydrodynamic diameter and zeta potential of POPC:POPG vesicles were similar upon the addition of both peptides. The mPEG-MAL conjugation of LyeTx I-bcys gave epimers, and it, together with LyeTx I-bPEG, showed clear α-helical profiles. While LyeTx I-bcys showed no significant change in amphipathicity compared to LyeTx I-b, LyeTx I-bPEG was found to have a slightly less clear separation between hydrophilic and hydrophobic faces. However, the similar conformational freedom of LyeTx I-b and LyeTx I-bPEG suggests that PEGylation does not cause significant structural changes. Overall, our structural and biophysical studies indicate that the PEGylation does not alter the mode of peptide interaction and maintains antimicrobial activity while minimizing tissue toxicity, which confirmed previous results obtained in vivo. Interestingly, significantly improved proteolytic resistance to trypsin and proteinase K was observed after PEGylation.

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The degradation of mesoporous silica nanoparticles (MSNs) in the biological milieu due to silica hydrolysis plays a fundamental role for the delivery of encapsulated drugs and therapeutics. However, little is known on the evolution of the pore arrangement in the MSNs in biologically relevant conditions. Small Angle X-ray scattering (SAXS) studies were performed on unmodified and PEGylated MSNs with a MCM-48 pore structure and average sizes of 140 nm, exposed to simulated body fluid solution (SBF) at pH 7.4 for different time intervals from 30 min to 24 h. Experiments were performed with silica concentrations below, at and over 0.14 mg/mL, the saturation concentration of silica in water at physiological temperature. At silica concentrations of 1 mg/mL (oversaturation), unmodified MSNs show variation in interpore distances over 6 h exposure to SBF, remaining constant thereafter. A decrease in radius of gyration is observed over the same time. Mesoporosity and radius of gyration of unmodified MSNs remain then unchanged up to 24 h. PEGylated MSNs at 1 mg/mL concentration show a broader diffraction peak but no change in the position of the peak is observed following 24 h exposure to SBF. PEGylated MSNs at 0.01 mg/mL show no diffraction peaks already after 30 min exposure to SBF, while at 0.14 mg/mL a small diffraction peak is present after 30 min exposure but disappears after 1 h.

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PEGylated protein purification with the required quality attributes has represented a bioengineering challenge and Affinity Monolith Chromatography (AMC) has never been exploited for this goal. This work reports the generation of a heparin-modified affinity monolith disk by reductive alkylation with raised ligand density for its use as chromatographic support in the separation of lysozyme PEGylation reactions (LPRs) with three different PEG sizes (1, 20 and 40 kDa). For immobilized heparin determination a modified toluidine colorimetric assay adapted to microplate format was proposed. The heparin modified-disk was able to differentiate positional isomers of 20 kDa mono-PEGylated lysozyme at neutral pH using a salt linear gradient. Identity of PEG-conjugates was verified by SDS-PAGE and positional isomers were partially characterized by peptide mapping mass spectrometry. 20 kDa mono-PEGylated lysozyme conjugate purity (99.69 ± 0.05%) was comparable with traditional chromatographic methods while productivity (0.0964 ± 0.0001 mg/mL*min) was increased up to 6.1 times compared to that obtained in heparin packed-bed affinity chromatography procedures. The proposed AMC method represents a reliable, efficient, easy-handling, fast and single-step operation for the analysis or preparative isolation of PEGylated proteins containing a heparin binding domain.

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Liposomal amphotericin B (AmB) or AmBisome® is the most effective and safe therapeutic agent for visceral leishmaniasis (VL), but its clinical efficacy is limited in cutaneous leishmaniasis (CL) and HIV/VL co-infection. The aim of this work was to develop a formulation of AmB in PEGylated liposomes and compare its efficacy to AmBisome® in a murine model of CL. Formulations of AmB in conventional and PEGylated liposomes were characterized for particle size and morphology, drug encapsulation efficiency and aggregation state. Those were compared to AmBisome® in Leishmania amazonensis-infected BALB/c mice for their effects on the lesion size growth and parasite load. The conventional and PEGylated formulations showed vesicles with 100-130 nm diameter and low polydispersity, incorporating more than 95% of AmB under the non-aggregated form. Following parenteral administration in the murine model of CL, the PEGylated formulation of AmB significantly reduced the lesion size growth and parasite load, in comparison to control groups, in contrast to conventional liposomal AmB. The PEGylated formulation of AmB was also effective when given by oral route on a 2-day regimen. This work reports for the first time that PEGylated liposomal AmB can improve the treatment of experimental cutaneous leishmaniasis by both parenteral and oral routes.

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Cytochrome c (Cyt-c), a small mitochondrial electron transport heme protein, has been employed in bioelectrochemical and therapeutic applications. However, its potential as both a biosensor and anticancer drug is significantly impaired due to poor long-term and thermal stability. To overcome these drawbacks, we developed a site-specific PEGylation protocol for Cyt-c. The PEG derivative used was a 5 kDa mPEG-NHS, and a site-directed PEGylation at the lysine amino-acids was performed. The effects of the pH of the reaction media, molar ratio (Cyt-c:mPEG-NHS) and reaction time were evaluated. The best conditions were defined as pH 7, 1:25 Cyt-c:mPEG-NHS and 15 min reaction time, resulting in PEGylation yield of 45% for Cyt-c-PEG-4 and 34% for Cyt-c-PEG-8 (PEGylated cytochrome c with 4 and 8 PEG molecules, respectively). Circular dichroism spectra demonstrated that PEGylation did not cause significant changes to the secondary and tertiary structures of the Cyt-c. The long-term stability of native and PEGylated Cyt-c forms was also investigated in terms of peroxidative activity. The results demonstrated that both Cyt-c-PEG-4 and Cyt-c-PEG-8 were more stable, presenting higher half-life than unPEGylated protein. In particular, Cyt-c-PEG-8 presented great potential for biomedical applications, since it retained 30-40% more residual activity than Cyt-c over 60-days of storage, at both studied temperatures of 4 °C and 25 °C.

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Biological drugs or biopharmaceuticals off patent open a large market for biosimilars and biobetters, follow-on biologics. Biobetters, in particular, are new drugs designed from existing ones with improved properties such as higher selectivity, stability, half-life and/or lower toxicity/immunogenicity. Glycosylation is one of the most used strategies to improve biological drugs, nonetheless bioconjugation is an additional alternative and refers to the covalent attachment of polymers to biological drugs. Extensive research on novel polymers is underway, nonetheless PEGylation is still the best alternative with the longest clinical track record. Innovative trends based on genetic engineering techniques such as fusion proteins and PASylation are also promising. In this review, all these alternatives wereexplored as well as current market trends, legislation and future perspectives.

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The liposomal amphotericin B (AmB) formulation, AmBisome®, still represents the best therapeutic option for cutaneous and visceral leishmaniasis. However, its clinical efficacy depends on the patient's immunological status, the clinical manifestation and the endemic region. Moreover, the need for parenteral administration, its side effects and high cost significantly limit its use in developing countries. This review reports the progress achieved thus far toward the understanding of the mechanism responsible for the reduced toxicity of liposomal AmB formulations and the factors that influence their efficacy against leishmaniasis. It also presents the recent advances in the development of more effective liposomal AmB formulations, including topical and oral liposome formulations. The critical role of the AmB aggregation state and release rate in the reduction of drug toxicity and in the drug efficacy by non-invasive routes is emphasized. This paper is expected to guide future research and development of innovative liposomal formulations of AmB.

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BACKGROUND PEGylation, defined as the covalent attachment of polyethylene glycol, allows the synthesis of PEGylated therapeutic proteins with enhanced physicochemical properties. Traditional alkylating Nterminal PEGylation reactions on amine groups involve the use of modified linear mono-methoxy polyethylene glycol (mPEG) molecules looking for the synthesis of mono-PEGylated products. However, this approach requires different purification steps since inevitably undesired cross-linked products are synthesized. Herein, we propose the use of reactive aqueous two-phase systems (ATPS) to produce and purify PEGylated therapeutic conjugates using Ribonuclease A (RNase A) as a model protein. RESULTS: Selected linear 5 kDa and 20 kDa mPEG ­ potassium phosphate systems were produced according to equilibrium data obtained from constructed binodal curves. All reactive systems were able to generate biphasic systems and to PEGylate RNase A. Two 5 kDa and two 20 kDa systems were selected based on the reaction yield percentage and the feasibility of purifying the mono-PEGylated RNase A from the diPEGylated and native RNase A by contrasting the differences in their partition behaviors. The remnant biological activity was of 94% and of 100% for the mono-PEGylated RNase A purified from the 5 kDa and 20 kDa mPEG systems when compared to the mono-PEGylated conjugate obtained by standard procurement methods.

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Interferons (IFNs) are cytokines involved in the immune response that act on innate and adaptive immunity. These proteins are natural cell-signaling glycoproteins expressed in response to viral infections, tumors, and biological inducers and constitute the first line of defense of vertebrates against infectious agents. They have been marketed for more than 30 years with considerable impact on the global therapeutic protein market thanks to their diversity in terms of biological activities. They have been used as single agents or with combination treatment regimens, demonstrating promising clinical results, resulting in 22 different formulations approved by regulatory agencies. The 163 clinical trials with currently active IFNs reinforce their importance as therapeutics for human health. However, their application has presented difficulties due to the molecules' size, sensitivity to degradation, and rapid elimination from the bloodstream. For some years now, work has been underway to obtain new drug delivery systems to provide adequate therapeutic concentrations for these cytokines, decrease their toxicity and prolong their half-life in the circulation. Although different research groups have presented various formulations that encapsulate IFNs, to date, there is no formulation approved for use in humans. The current review exhibits an updated summary of all encapsulation forms presented in the scientific literature for IFN-α, IFN-ß, and IFN-γ, from the year 1996 to the year 2021, considering parameters such as: encapsulating matrix, route of administration, target, advantages, and disadvantages of each formulation.

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Proteins, which have inherent biorecognition properties, have long been used as therapeutic agents for the treatment of a wide variety of clinical indications. Protein modification through covalent attachment to different moieties improves the therapeutic's pharmacokinetic properties, affinity, stability, confers protection against proteolytic degradation, and increases circulation half-life. Nowadays, several modified therapeutic proteins, including PEGylated, Fc-fused, lipidated, albumin-fused, and glycosylated proteins have obtained regulatory approval for commercialization. During its manufacturing, the purification steps of the therapeutic agent are decisive to ensure the quality, effectiveness, potency, and safety of the final product. Due to the robustness, selectivity, and high resolution of chromatographic methods, these are recognized as the gold standard in the downstream processing of therapeutic proteins. Moreover, depending on the modification strategy, the protein will suffer different physicochemical changes, which must be considered to define a purification approach. This review aims to deeply analyze the purification methods employed for modified therapeutic proteins that are currently available on the market, to understand why the selected strategies were successful. Emphasis is placed on chromatographic methods since they govern the purification processes within the pharmaceutical industry. Furthermore, to discuss how the modification type strongly influences the purification strategy, the purification processes of three different modified versions of coagulation factor IX are contrasted.

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The metabolic function of catalase (CAT) is to prevent oxidative damage to tissues through the hydrolysis of hydrogen peroxide, which is a strong oxidizing agent. It has been suggested as an alternative to treat skin diseases related to oxidative stress, such as vitiligo. Owing to the instability associated to the protein nature, topical use of CAT is challenging and, in this sense, PEGylation can be an interesting alternative. Here, we conjugated CAT to methoxy-poly(ethylene oxide) (mPEG) of 10, 20 and 40 kDa, by means of a nucleophilic attack of ε-amino groups to an electron-deficient carbonyl group of the reactive PEG, resulting in site specifically PEGylated bioconjugates. PEGylation yields ranged from 31% ± 2% for CAT-PEG40 to 59% ± 4% for CAT-PEG20 and were strongly affected by the reaction pH owing to the protonation/deprotonation state of primary amines of lysine and N-terminal residues. PEGylated conjugates were purified by size-exclusion chromatography (purity > 95%) and characterized by circular dichroism. Irrespectively of MW, PEG did not affected CAT secondary and tertiary structure, but a decrease in specific activity was observed, more pronounced when PEGs of higher MWs were used. However, this loss of activity is compensated by the increased long-term stability, with a gain of >5 times in t1/2. In vitro antioxidant activity of CAT-PEG20 showed complete elimination of lipid peroxidation at the skin upper layer (stratum corneum) suitable for a topical use to treat vitiligo, as well as other skin conditions related to oxidative stress.

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The enzyme L-asparaginase (ASNase) is broadly applied as a drug to treat acute lymphoblastic leukemia, as well as in the food industry to avoid acrylamide formation in baked and fried food. In the present work, ASNase was covalently attached to polyethylene glycol (PEG) of different molecular weights (ASNase-PEG-5, ASNase-PEG-10, ASNase-PEG-20, and ASNase-PEG-40) at the N-terminal portion (monoPEGylation). Native and PEGylated forms were analyzed regarding thermodynamics and thermostability based on enzyme activity measurements. ASNase (native and PEGylated) presented maximum activity at 40 °C and denaturation followed a first-order kinetics. Based on these results, the activation energy for denaturation (E*d) was estimated and higher values were observed for PEGylated forms compared to the native ASNase, highlighting the ASNase-PEG10 with a 4.24-fold increase (48.85 kJ.mol-1) in comparison to the native form (11.52 kJ.mol-1). The enzymes were evaluated by residual activity over time (21 days) under different storage temperatures (4 and 37 °C) and the PEGylated conjugates remained stable after the 21 days. Thermodynamic parameters like enthalpy (ΔH‡), entropy (ΔS‡) and Gibbs free energy (ΔG‡) of ASNase (native and PEGylated) irreversible denaturation were also investigated. Higher - and positive - values of Gibbs free energy were found for the PEGylated conjugates (61.21 a 63.45 kJ.mol-1), indicating that the process of denaturation was not spontaneous. Enthalpy also was higher for PEGylated conjugates (18.84 a 46.08 kJ.mol-1), demonstrating the protective role of PEGylation. As for entropy, the negative values were more elevated for native ASNase (-0.149 J/mol.K), pointing out that the denaturation process enhanced the randomness and aggregation of the system, which was observed by circular dichroism. Thus, PEGylation proved its potential to increase ASNase thermostability

A enzima L-asparaginase (ASNase) é amplamente usada como medicamento para tratamento da leucemia linfoblástica aguda, bem como na indústria de alimentos para evitar a formação de acrilamida em alimentos cozidos e fritos. No presente trabalho, ASNase foi covalentemente ligada ao polímero poli(etilenoglicol) (PEG) de diferentes massas moleculares (ASNase-PEG-5, ASNase-PEG- 10, ASNase-PEG-20, and ASNase-PEG-40) na região N-terminal (monoPEGuilação) a fim de se estudar os efeitos da PEGuilação na termoestabilidade da enzima. As formas PEGuiladas e nativa foram analisadas em relação à termodinâmica e termoestabilidade a partir de atividade enzimática. A ASNase (nativa e PEGuilada) apresentou atividade máxima a 40 °C e a desnaturação ocorreu por cinética de primeira ordem. Com base nesses resultados, a energia de ativação para desnaturação (E*d) foi estimada e maiores valores foram observados para as formas PEGuiladas em comparação à enzima nativa, destacando-se a ASNase-PEG10 com aumento de 4.24 vezes (48.85 kJ.mol-1) em comparação com a forma nativa in (11.52 kJ.mol mol-1). As enzimas foram avaliadas por sua atividade residual ao longo do tempo em diferentes temperaturas de armazenamento (4 e 37 °C) e os conjugados PEGuilados mostraram-se mais estáveis após os 21 dias de ensaio. Parâmetros termodinâmicos como entalpia (ΔH‡) de desnaturação irreversível foram analisados. Valores maiores - e ), entropia (ΔS‡) de desnaturação irreversível foram analisados. Valores maiores - e ) e energia livre de Gibbs (ΔG‡) de desnaturação irreversível foram analisados. Valores maiores - e positivos - da energia livre de Gibbs foram encontrados para os conjugados PEGuilados (61.21 a 63.45 kJ.mol-1), indicando que o processo de desnaturação não ocorreu de forma espontânea. A entalpia também foi maior para os conjugados PEGuilados (18.84 a 46.08 kJ.mol-1), demonstrando o efeito protetivo da PEGuilação. Já para a entropia, os valores negativos foram mais elevados para a ASNase nativa (-0.149 J/mol.K), apontando que o processo de desnaturação aumentou a aleatoriedade e agregação do sistema, o que foi confirmado pelo dicroísmo circular. Dessa forma, a PEGuilação revelou o seu potencial de aumento de termoestabilidade para a ASNase

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As infecções relacionadas à assistência à saúde (IRAS) podem ser causadas por bactérias, vírus e fungos, sendo de extrema importância para o sistema de tratamento e pacientes. Com o alarmante avanço no surgimento de bactérias resistentes, tem havido uma preocupação crescente com as IRAS de origem bacteriana. Nesse sentido, várias pesquisas buscam alternativas para os fármacos antimicrobianos convencionais, sendo que os peptídeos antimicrobianos (AMPs), como a lunatina-1, aparecem como moléculas promissoras. No entanto, os AMPs geralmente apresentam rápida degradação proteolítica no trato gastrointestinal e meia-vida curta na corrente sanguínea, principais fatores limitantes para sua aplicação no tratamento de IRAS. Entre as estratégias empregadas para superar esses inconvenientes, a PEGuilação apresenta-se como alternativa eficaz que aumenta o tempo de circulação in vivo dos AMPs, resultando na melhora farmacocinética e, em alguns casos, também farmacodinâmica. A PEGuilação consiste na ligação covalente de cadeias de polietileno glicol (PEG) ao peptídeo, que pode ser efetuada por meio de uma reação aleatória ou sítio-específica. Neste trabalho, desenvolveu-se uma PEGuilação sítio-específica no N-terminal da lunatina-1 empregando-se mPEG-NHS de 2 kDa em tampão fosfato 100 mM, visando o aumento da solibilidade deste peptídeo, bem como para avaliar sua ação antimicrobiana. Com relação à reação de PEGuilação, avaliou-se a influência da razão molar PEG:peptídeo (10:1 ou 15:1) a pH 8,5. Foi obtido um rendimento de PEGuilação de 92%, através da análise por RP-HPLC quantitativo. Quanto à purificação da lunatina-1 PEGuilada, foi empregada a técnica semi-preparativa de RP-HPLC utilizando a coluna C18. A caracterização da lunatina-1 PEGuilada, incluindo determinação do grau de PEGuilação, foi realizada por MALDI-TOF Autoflex Speed (Bruker), mostrando que a molécula foi monoPEGuilada na região N-terminal. A atividade antimicrobiana de lunatina-1 livre e bioconjugada frente a diferentes cepas bacterianas, sendo duas Gram-negativas (ATCC 25922 de Escherichia coli e ATCC 9027 de Pseudomonas aeruginosa) e uma Gram-positiva (CECT 239 de Staphylococcus aureus), foi estudada por determinação da concentração inibitória mínima (CIM) em microplaca, sendo que foram obtidos valores de CIM de 86 e 140 µM para o peptídeo liver e PEGuilado, respetivamente. O potencial hemolítico também foi estudado, sendo que a forma PEGuilada mostrou significativa redução da atividade hemolítica em comparação à forma livre. Em suma, a PEGuilação da lunatina-1, aumenta a sua solubilidade e reduz a atividade hemolítica. Porém, para viabilizar esta estratégia a PEGuilação deve ser reversível, pois a conjugação ao polímero reduz atividade antimicrobiana

Health care-related infections (HAIs) caused by bacteria, viruses and fungi are extremely important for patients and health systems. With the alarming advance in the emergence of resistant bacteria, a growing concern with HAIs of bacterial origin is observed. In this sense, several studies investigate alternatives to conventional antimicrobial drugs and antimicrobial peptides (AMPs), such as lunatin-1, appear as promising molecules. However, AMPs generally show rapid proteolytic degradation in the gastrointestinal tract and short half-life in the bloodstream, the main limiting factors for their therapeutic application to treat HAIs. Among the strategies used to overcome these drawbacks, PEGylation presents itself as an effective alternative that increases the in vivo circulation time of AMPs, resulting in improved pharmacokinetics and, in some cases, also pharmacodynamics. PEGylation consists on the covalent attachment of polyethylene glycol (PEG) chains to the peptide, which can be carried out by means of a random or site-specific reaction. In this work, a site-specific PEGylation was developed at the N-terminus of lunatin-1 using 2 kDa mPEG-NHS to increase the solubility of this peptide, as well as to evaluate its antimicrobial activity. Regarding the PEGylation reaction, the influence of the molar ratio PEG: peptide (10: 1 or 15: 1) at pH 8.5 was evaluated and a PEGylation yield of 92% was obtained, based on quantitative RP-HPLC analysis. As for the purification of PEGylated lunatin-1, semi-preparative RP-HPLC was used. The characterization of PEGylated lunatin-1, including determination of the degree of PEGylation, was performed by MALDI-TOF Autoflex Speed (Bruker), showing that the peptide was monoPEGylated in the N-terminal region. The antimicrobial activity of free and bioconjugated lunatin-1 against different bacterial strains, two Gram-negative (ATCC 25922 from Escherichia coli and ATCC 9027 from Pseudomonas aeruginosa), and one Gram positive (CECT 239 from Staphylococcus aureus), was studied by determining the minimum inhibitory concentration (MIC) in a microplate, resulting in MIC values of 86 and 140 µM for the free and PEGylated peptide, respectively. The hemolytic potential was also studied and the PEGylated form showed a significant reduction in hemolytic activity compared to the free form. In short, the PEGylation of lunatin-1 increases its solubility and reduces hemolytic activity. However, to make this strategy feasible, PEGylation must be reversible, since the conjugation to the polymer reduces antimicrobial activity

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Resumo A PEGuilação, reação química de conjugação com a molécula de polietilenoglicol (PEG) ou polietilenoglicol metil éter (mPEG), tem sido amplamente aplicada pelas indústrias farmacêuticas como estratégia de melhoria das propriedades farmaco-cinéticas de compostos bioativos. O PEG é um polímero que possui um esqueleto de poliéter quimicamente inerte e que apresenta grupos hidroxilas (-OH) em suas extremidades. Assim, o PEG para tornar-se apto como reagente de conjugação deve ser ativado com um grupo funcional que seja reativo. Nesse sentido, a bromoaceti-lação apresenta-se como uma alternativa para a funcionalização do PEG. Portanto, nesse trabalho objetivamos descrever em detalhes os procedimentos e o mecanismo de reação envolvida na funcionalização do mPEG, através da reação de bromoacetilação. Além do mais, estudamos a aplicação do MALDI-ToF para a caracterização do produto ativado. Após a bromoacetilação, por um procedimento adaptado, obteve-se o bromoacetil-mPEG-éster, com rendimento bruto de 56,78%. Análises posteriores, por espectrometria de massas por MALDI-ToF, possibilitaram identificar e caracterizar o produto bromoacetilado. Entre as condições de reação, o controle de temperatura (-10 °C a 0 °C) mostrou-se eficaz favorecendo a adição nucleofílica essencial à bromoacetilação. Assim, concluímos que o controle da baixa temperatura reacional é um fator chave para o favorecimento da adição nucleofílica à carbonila e, portanto, essencial na obtenção do mPEG funcionalizado via bromoacetilação. Estudos posteriores serão necessários, no entanto, para confirmar se o mPEG esterificado, nessas condições, poderá ser utilizado na conjugação com moléculas de natureza proteica ou peptídica, por meio de substituição nucleofílica bimolecular.

SUMMARY PEGylation, a chemical reaction of conjugation with the polyethylene glycol molecule (PEG), has been widely applied by the pharmaceutical industries as a strategy to improve the pharmacokinetic properties of bioactive compounds. PEG is a polymer that has a chemically inert polyether backbone and hydroxyl groups (-OH) at its ends. Thus, PEG to become fit as a reagent for conjugation must be activated with a functional group that is reactive. In this sense, bromoacetylation presents itself as an alternative for the functionalization of PEG. Therefore, in this study we aim to describe in detail the procedures and reaction mechanism involved in the functionalization of mPEG through the bromoacetylation reaction. In addition, we used the spectrometric technique, by MALDI-ToF, for the characterization of the activated product. After applying an adapted bromoacetylation procedure, bromoacetyl-mPEG-ester was obtained with a yield of 56.78%. Subsequent analyzes of MALDI-ToF mass spectrometry were able to correctly identify and characterize the bromoacety-lated product. Among the reaction conditions, temperature control (from -10 °C to 0 °C) was effective in favoring the essential nucleophilic addition to bromoacetylation. Thus, we conclude that the control of the low reaction temperature is a key factor in favoring the nucleophilic addition to carbonyl and, therefore, obtaining a favorable conversion to functionalized PEG via bromoacetylation. Further studies, however, will be necessary to confirm whether PEG esterified with these conditions can be used in conjunction with molecules of a protein or peptide nature by means of bimolecular nucleophilic substitution.

RESUMEN La PEGilación, una reacción química de conjugación con la molécula de polietilenglicol (PEG), ha sido ampliamente aplicada por las industrias farmacéuticas como una estrategia para mejorar las propiedades farmacocinéticas de los compuestos bioactivos. El PEG es un polímero formado por un esqueleto de poliéter químicamente inerte con grupos hidroxilo (-OH) en sus extremos. Por lo tanto, para usar el PEG como reactivo de conjugación debe activarse con un grupo funcional que sea reactivo. En este sentido, la bromoacetilación es una alternativa para la funcionalización de PEG. De esta manera, en este trabajo nuestro objetivo es describir en detalle los procedimientos y el mecanismo de reacción involucrados en la funcionalización de PEG a través de la reacción de bromoacetilación. Además, estudiamos la aplicación de MALDI-ToF para la caracterización del producto activado. Después de aplicar un procedimiento de bromoacetilación adaptado, se obtuvo bromoacetil-mPEG-éster con un rendimiento bruto de 56,78%. Los análisis posteriores de espectrometría de masas por MALDI-ToF pudieron identificar y caracterizar correctamente el producto bromoacetilado. Entre las condiciones de reacción, el control de la temperatura (desde -10 °C hasta 0 °C) fue eficaz para favorecer la adición nucleofílica esencial a la bromoacetilación. Así, concluimos que el control de la baja temperatura de reacción es un factor clave para favorecer la adición nucleofílica al carbonilo y, por lo tanto, esencial para obtener el mPEG funcionalizado mediante la bromoacetilación. Sin embargo, serán necesarios más estudios para confirmar si el mPEG esterificado en estas condiciones puede usarse junto con moléculas de naturaleza proteica o peptídica por medio de la sustitución nucleófila bimolecular.

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Intranasal administration of mucus-penetrating nanoparticles is an emerging trend to increase drug delivery to the brain. In order to overcome rapid nasal mucociliary clearance, low epithelial permeation, and local enzymatic degradation, we investigated the influence of PEGylation on nose-to-brain delivery of polycaprolactone (PCL) nanoparticles (PCL-NPs) encapsulating bexarotene, a potential neuroprotective compound. PEGylation with 1, 3, 5, and 10% PCL-PEG did not affect particle diameter or morphology. Upon incubation with artificial nasal mucus, only 5 and 10% of PCL-PEG coating were able to ensure NP stability and homogeneity in mucus. Rapid mucus-penetrating ability was observed for 98.8% of PCL-PEG5% NPs and for 99.5% of PCL-PEG10% NPs. Conversely, the motion of non-modified PCL-NPs was markedly slower. Fluorescence microscopy showed that the presence of PEG on NP surface did not reduce their uptake by RMPI 2650 cells. Fluorescence tomography images evidenced higher translocation into the brain for PCL-PEG5% NPs. Bexarotene loaded into PCL-PEG5% NPs resulted in area under the curve in the brain (AUCbrain) 3 and 2-fold higher than that for the drug dispersion and for non-PEGylated NPs (p < 0.05), indicating that approximately 4% of the dose was directly delivered to the brain. Combined, these results indicate that PEGylation of PCL-NPs with PCL-PEG5% is able to reduce NP interactions with the mucus, leading to a more efficient drug delivery to the brain following intranasal administration. Graphical abstract.

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Crisantaspase is an asparaginase enzyme produced by Erwinia chrysanthemi and used to treat acute lymphoblastic leukemia (ALL) in case of hypersensitivity to Escherichia coli l-asparaginase (ASNase). The main disadvantages of crisantaspase are the short half-life (10 H) and immunogenicity. In this sense, its PEGylated form (PEG-crisantaspase) could not only reduce immunogenicity but also improve plasma half-life. In this work, we developed a process to obtain a site-specific N-terminal PEGylated crisantaspase (PEG-crisantaspase). Crisantaspase was recombinantly expressed in E. coli BL21(DE3) strain cultivated in a shaker and in a 2-L bioreactor. Volumetric productivity in bioreactor increased 37% compared to shaker conditions (460 and 335 U L-1  H-1 , respectively). Crisantaspase was extracted by osmotic shock and purified by cation exchange chromatography, presenting specific activity of 694 U mg-1 , 21.7 purification fold, and yield of 69%. Purified crisantaspase was PEGylated with 10 kDa methoxy polyethylene glycol-N-hydroxysuccinimidyl (mPEG-NHS) at different pH values (6.5-9.0). The highest N-terminal pegylation yield (50%) was at pH 7.5 with the lowest poly-PEGylation ratio (7%). PEG-crisantaspase was purified by size exclusion chromatography and presented a KM value three times higher than crisantaspase (150 and 48.5 µM, respectively). Nonetheless, PEG-crisantaspase was found to be more stable at high temperatures and over longer periods of time. In 2 weeks, crisantaspase lost 93% of its specific activity, whereas PEG-crisantaspase was stable for 20 days. Therefore, the novel PEG-crisantaspase enzyme represents a promising biobetter alternative for the treatment of ALL.

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