Cláudia Martins

Functionalizing PLGA and PLGA Derivatives for Drug Delivery and Tissue Regeneration Applications

Poly(lactic-co-glycolic) acid (PLGA) is one of the most versatile biomedical polymers, already approved by regulatory authorities to be used in human research and clinics. Due to its valuable characteristics, PLGA can be tailored to acquire desirable features for control bioactive payload or scaffold matrix. Moreover, its chemical modification with other polymers or bioconjugation with molecules may render PLGA with functional properties that make it the Holy Grail among the synthetic polymers to be applied in the biomedical field. In this review, the physical-chemical properties of PLGA, its synthesis, degradation, and conjugation with other polymers or molecules are revised in detail, as well as its applications in drug delivery and regeneration fields. A particular focus is given to successful examples of products already on the market or at the late stages of trials, reinforcing the potential of this polymer in the biomedical field.

Chemical modification of drug molecules as strategy to reduce interactions with mucus

Abstract Many drug molecules possess inadequate physical‐chemical characteristics that prevent to surpass the viscous mucus layer present in the surface of mucosal tissues. Due to mucus protective role and its fast turnover, these drug molecules end up being removed from the body before being absorbed and, thus, before exerting any physiologic affect. Envisaging a better pharmacokinetics profile, chemical modifications, to render drug a more mucopenetrating character, have been introduced to drug molecules backbone towards more effective therapies. Mucus penetration increases when drug molecules are provided with net‐neutral charge, when they are conjugated with mucolytic agents and through modifications that makes them resistant to enzymes present in mucus, with the overall increase of their hydrophilicity and the decrease of their molecular weight. All of these characteristics act as a whole and influence each other so they must be well thought when drug molecules are being designed for mucosal delivery. Graphical abstract Figure. No Caption available.

Therapeutic Monoclonal Antibodies Delivery for the Glioblastoma Treatment

Glioblastoma multiforme (GBM) is the most common and challenging primary malignant brain tumor, being the median overall survival between 10 and 14 months due to its invasive characteristics. GBM treatment is mainly based on the maximal surgical resection and radiotherapy associated to chemotherapy. Monoclonal antibodies (mAbs) have been used in chemotherapy protocols for GBM treatment in order to improve immunotherapy and antiangiogenic processes. High specificity and affinity of mAbs for biological targets make them highly used for brain tumor therapy. Specifically, antiangiogenic mAbs have been wisely indicated in chemotherapy protocols because GBM is the most vascularized tumors in humans with high expression of cytokines. However, mAb-based therapy is not that effective due to the aggressive spread of the tumor associated to the difficulty in the access of mAb into the brain (due to the blood-brain barrier). For that reason, nanobiotechnology has played an important role in the treatment of several tumors, mainly in the tumors of difficult access, such as GBM. In this chapter will be discussed strategies related with nanobiotechnology applied to the mAb delivery and how these therapeutics can improve the GBM treatment and life quality of the patient.

Using microfluidic platforms to develop CNS-targeted polymeric nanoparticles for HIV therapy

ABSTRACT The human immunodeficiency virus (HIV) uses the brain as reservoir, which turns it as a promising target to fight this pathology. Nanoparticles (NPs) of poly(lactic‐co‐glycolic) acid (PLGA) are potential carriers of anti‐HIV drugs to the brain, since most of these antiretrovirals, as efavirenz (EFV), cannot surpass the blood‐brain barrier (BBB). Forasmuch as the conventional production methods lack precise control over the final properties of particles, microfluidics emerged as a prospective alternative. This study aimed at developing EFV‐loaded PLGA NPs through a conventional and microfluidic method, targeted to the BBB, in order to treat HIV neuropathology. Compared to the conventional method, NPs produced through microfluidics presented reduced size (73nm versus 133nm), comparable polydispersity (around 0.090), less negative zeta‐potential (−14.1mV versus −28.0mV), higher EFV association efficiency (80.7% versus 32.7%) and higher drug loading (10.8% versus 3.2%). The microfluidics‐produced NPs also demonstrated a sustained in vitro EFV release (50% released within the first 24h). NPs functionalization with a transferrin receptor‐binding peptide, envisaging BBB targeting, proved to be effective concerning nuclear magnetic resonance analysis (&dgr; = −0.008ppm; &dgr; = −0.017ppm). NPs demonstrated to be safe to BBB endothelial and neuron cells (metabolic activity above 70%), as well as non‐hemolytic (1–2% of hemolysis, no morphological alterations on erythrocytes). Finally, functionalized nanosystems were able to interact more efficiently with BBB cells, and permeability of EFV associated with NPs through a BBB in vitro model was around 1.3‐fold higher than the free drug.

Development of a PEGylated-based Platform for Efficient Delivery of Dietary Antioxidants Across the Blood–Brain Barrier

The uptake and transport of dietary antioxidants remains the most important setback for their application in therapy. To overcome the limitations, a PEGylated-based platform was developed to improve the delivery properties of two dietary hydroxycinnamic (HCA) antioxidants-caffeic and ferulic acids. The antioxidant properties of the new polymer-antioxidant conjugates (PEGAntiOxs), prepared by linking poly(ethylene glycol) (PEG) to the cinnamic acids by a one-step Knovenagel condensation reaction, were evaluated. PEGAntiOxs present a higher lipophilicity than the parent compounds (caffeic and ferulic acids) and similar, or higher, antioxidant properties. PEGAntiOxs were not cytotoxic at the tested concentrations in SH-SY5Y, Caco-2, and hCMEC/D3 cells. By contrast, cytotoxic effects in hCMEC/D3 and SH-SY5Y cells were observed, at 50 and 100 μM, for caffeic and ferulic acids. PEGAntiOxs operate as antioxidants against several oxidative stress-cellular inducers in a neuronal cell-based model, and were able to inhibit glycoprotein-P in Caco-2 cells. PEGAntiOxs can cross hCMEC/D3 monolayer cells, a model of the blood-brain barrier (BBB) endothelial membrane. In summary, PEGAntiOxs are valid antioxidant prototypes that can uphold the antioxidant properties of HCAs, reduce their cytotoxicity, and improve their BBB permeability. PEGAntiOxs can be used in the near future as drug candidates to prevent or slow oxidative stress associated with neurodegenerative diseases.

PEGylated PLGA nanoparticles as a smart carrier to increase the cellular uptake of a coumarin-based monoamine oxidase B inhibitor

Despite research efforts to discover new drugs for Parkinson treatment, the majority of candidates fail in preclinical and clinical trials due to inadequate pharmacokinetic properties, namely blood-brain barrier permeability. Within the high demand to introduce new drugs to market, nanotechnology can be used as a solution. Accordingly, PEGylated PLGA nanoparticles (NPs) were used as a smart delivery carrier to solve the suboptimal aqueous solubility, which precludes its use in in vivo assays, of a potent, reversible, and selective monoamine oxidase B inhibitor (IMAO-B) (coumarin C75, IC50 = 28.89 ± 1.18 nM). Long-term stable PLGA@C75 NPs were obtained by nanoprecipitation method, with sizes around 105 nm and a zeta potential of -10.1 mV. The encapsulation efficacy was around 50%, achieving the final C75 concentration of 807 ± 30 μM in the nanoformulation, which corresponds to a therapeutic concentration 27828-fold higher than its IC50 value. Coumarin C75 showed cytotoxic effects at 50 μM after 48 and 72 h of exposure in SH-SY5Y, Caco-2, and hCMEC/D3 cell lines. Remarkably, no cytotoxic effects were observed after nanoencapsulation. Furthermore, the data obtained from the P-gp-Glo assay and the cellular uptake studies showed that C75 is a P-glycoprotein (P-gp) substrate having a lower uptake profile in intestinal and brain endothelial cells. Moreover, it was shown that this membrane transporter influences C75 permeability profile in Caco-2 and hCMEC/D3 cells. Interestingly, PLGA NPs inhibited P-gp and were able to cross intestinal and brain membranes allowing the successful transport of C75 through this type of biological barriers. Overall, this work showed that nanotechnology can be used to solve drug discovery related drawbacks.