Preparation, characterization and in vitro release kinetics of polyaspartamide-based conjugates containing antimalarial and anticancer agents for combination therapy

Progress in Treatment and Diagnostics of Infectious Disease with Polymers

In this era of advanced technology and innovation, infectious diseases still cause significant morbidity and mortality, which need to be addressed. Despite overwhelming success in the development of vaccines, transmittable diseases such as tuberculosis and AIDS remain unprotected, and the treatment is challenging due to frequent mutations of the pathogens. Formulations of new or existing drugs with polymeric materials have been explored as a promising new approach. Variations in shape, size, surface charge, internal morphology, and functionalization position polymer particles as a revolutionary material in healthcare. Here, an overview is provided of major diseases along with statistics on infection and death rates, focusing on polymer-based treatments and modes of action. Key issues are discussed in this review pertaining to current challenges and future perspectives.

Combining Doxorubicin-Conjugated Polymeric Nanoparticles and 5-Aminolevulinic Acid for Enhancing Radiotherapy against Lung Cancer

Radiation therapy (RT) concurrent with chemotherapy improves local lung cancer control but may cause systemic toxicity. There is an unmet clinical need of treatments that can selectively sensitize cancer cells to RT. Herein, we explored a radiosensitizing strategy that combines doxorubicin (DOX)-encapsulated polyaspartamide nanoparticles and 5-aminolevulinic acid (5-ALA). The DOX-polyaspartamide nanoparticles were coupled with NTS_mut, a ligand specific to neurotensin receptor type 1 (NTSR1), for lung cancer targeting. DOX was coupled to the polymer backbone through a pH-sensitive hydrazone linker, which allows for controlled release of the drug in an acidic tumor micromovement. Meanwhile, 5-ALA accumulates in the cancer cell's mitochondria, forming protoporphyrin (PpIX) that amplifies RT-induced oxidative stress. When tested in vitro in H1299 cells, DOX-encapsulated nanoparticles in conjugation with 5-ALA enhanced cancer cell killing owing to the complementary radiosensitizing effects of DOX and 5-ALA. In vivo studies confirmed that the combination improved tumor suppression relative to RT alone without causing toxicity to normal tissues. Overall, our study suggests an effective and selective radiosensitizing approach.

Polymeric Nanoparticle Based Diagnosis and Nanomedicine for Treatment and Development of Vaccines for Cerebral Malaria: A Review on Recent Advancement

Cerebral malaria occurs due to Plasmodium falciparum infection, which causes 228 million infections and 450,000 deaths worldwide every year. African people are mostly affected with nearly 91% cases, of which 86% are pregnant women and infants. India and Brazil are the other two countries severely suffering from malaria endemicity. Commonly used drugs have severe side effects, and unfortunately no suitable vaccine is available in the market today. In this line, this review is focused on polymeric nanomaterials and nanocapsules that can be used for the development of effective diagnostic strategies, nanomedicines, and vaccines in the management of cerebral malaria. Further, this review will help scientists and medical professionals by updating the status on the development stages of polymeric nanoparticle based diagnostics, nanomedicines, and vaccines and strategies to eradicate cerebral malaria. In addition to this, the predominant focus of this review is antimalarial agents based on polymer nanomedicines that are currently in the preclinical and clinical trial stages, and potential developments are suggested as well. This review further will have an important social and commercial impact worldwide for the development of polymeric nanomedicines and strategies for the treatment of cerebral malaria.

Integration of iron oxide nanoparticles and polyaspartamide biopolymer for MRI image contrast enhancement and an efficient drug-delivery system in cancer therapy

We integrate superparamagnetic iron oxide nanoparticles with polyaspartamide (PA) biopolymer to form a biological construct that functions as a tracking, targeting and drug-delivery system for cancer diagnosis and therapy. Iron oxide nanoparticles with uniformly distributed average spherical diameters of around 10 nm and superparamagnetic characteristics play a key role in increasing the transverse 1/T ₂ relaxation rate or darkening the T ₂-weighted MR image for cancer diagnosis using MRI. In in vitro MRI testing on cancer cells, the MR images of samples with the bio-constructshow a much clearer contrast effect than those of controls. The PA biopolymer plays an essential role in enhancing the hydrophilicity and biocompatibility of the bio-construct. In addition, as a multifunctional polymer, PA is conjugated with biotin and doxorubicin (Dox) functional groups to enhance targeting and impairment of cancer cells. In in vivo testing on cancer tumors, injection with the bio-construct decreased the magnitude of cancer tumor volume growth by three times compared with that of uninjected controls. The physicochemical characteristics of the bio-construct and the roles of biotin and Dox functional groups are examined and discussed in detail.

Nanomedicines to Deliver mRNA: State of the Art and Future Perspectives

The use of messenger RNA (mRNA) in gene therapy is increasing in recent years, due to its unique features compared to plasmid DNA: Transient expression, no need to enter into the nucleus and no risk of insertional mutagenesis. Nevertheless, the clinical application of mRNA as a therapeutic tool is limited by its instability and ability to activate immune responses; hence, mRNA chemical modifications together with the design of suitable vehicles result essential. This manuscript includes a revision of the strategies employed to enhance in vitro transcribed (IVT) mRNA functionality and efficacy, including the optimization of its stability and translational efficiency, as well as the regulation of its immunostimulatory properties. An overview of the nanosystems designed to protect the mRNA and to overcome the intra and extracellular barriers for successful delivery is also included. Finally, the present and future applications of mRNA nanomedicines for immunization against infectious diseases and cancer, protein replacement, gene editing, and regenerative medicine are highlighted.

Fully amino acid-based hydrogel as potential scaffold for cell culturing and drug delivery

Polymer hydrogels are ideal scaffolds for both tissue engineering and drug delivery. A great advantage of poly(amino acid)-based hydrogels is their high similarity to natural proteins. However, their expensive and complicated synthesis often limits their application. The use of poly(aspartic acid) (PASP) seems an appropriate solution for this problem due to the relatively cheap and simple synthesis of PASP. Using amino acids not only as building blocks in the polymer backbone but also as cross-linkers can improve the biocompatibility and the biodegradability of the hydrogel. In this paper, PASP cross-linked with cystamine (CYS) and lysine-methylester (LYS) was introduced as fully amino acid-based polymer hydrogel. Gels were synthesized employing six different ratios of CYS and LYS. The pH dependent swelling degree and the concentration of the elastically active chain were determined. After reduction of the disulfide bonds of CYS, the presence of thiol side groups was also detected. To determine the concentration of the reactive cross-linkers in the hydrogels, a new method based on the examination of the swelling behavior was established. Using metoprolol as a model drug, cell proliferation and drug release kinetics were studied at different LYS contents and in the presence of thiol groups. The optimal ratio of cross-linkers for the proliferation of periodontal ligament cells was found to be 60-80% LYS and 20-40% CYS. The reductive conditions resulted in an increased drug release due to the cleavage of disulfide bridges in the hydrogels. Consequently, these hydrogels provide new possibilities in the fields of both tissue engineering and controlled drug delivery.

Combination Therapy Strategies for the Treatment of Malaria

Malaria is a vector- and blood-borne infection that is responsible for a large number of deaths around the world. Most of the currently used antimalarial therapeutics suffer from drug resistance. The other limitations associated with the currently used antimalarial drugs are poor drug bioavailability, drug toxicity, and poor water solubility. Combination therapy is one of the best approaches that is currently used to treat malaria, whereby two or more therapeutic agents are combined. Different combination therapy strategies are used to overcome the aforementioned limitations. This review article reports two strategies of combination therapy; the incorporation of two or more antimalarials into polymer-based carriers and hybrid compounds designed by hybridization of two antimalarial pharmacophores.

Kinetics of dopamine release from poly(aspartamide)-based prodrugs

Preparation of novel biocompatible and biodegradable polymer-based prodrugs that can be applied in complex drug delivery systems is one of the most researched fields in pharmaceutics. The kinetics of the drug release strongly depends on the physicochemical parameters of prodrugs as well as environmental properties, therefore precise kinetical description is crucial to design the appropriate polymer prodrug formula. The aim of the present study was to investigate the dopamine release from different poly(aspartamide) based dopamine drug conjugates in different environments and to work out a kinetic description which can be extended to describe drug release in similar systems. Poly(aspartamide) was conjugated with different amounts of dopamine. In order to alter the solubility of the conjugates, 2-aminoethanol was also grafted to the main chain. Chemical structure as well as physical properties such as solubility, lipophilicity measurements and thermogravimetric analysis has been carried out. Kinetics of dopamine release from the macromolecular prodrugs which has good water solubility has been studied and compared in different environments (phosphate buffer, Bromelain and α-Chymotrypsin). It was found that the kinetics of release in those solutions can be satisfactorily described by first order reaction rate. For poorly-soluble conjugates, the release of dopamine was considered as a result of coupling of diffusion and chemical reaction. Besides the time dependence of dopamine cleavage, a practical quantity, the half-life of the release of loading capacity has been introduced and evaluated. It was found, that dopamine containing macromolecular prodrugs exhibit prolonged release kinetics and the quantitative description of the kinetics, including the most important physical parameters provides a solid base for future pharmaceutical and medical studies.

STATEMENT OF SIGNIFICANCE

Poly(aspartamide) based polymer-drug conjugates are promising for controlled and prolonged drug delivery due to their biocompatibility and biodegradability. In this study different poly(aspartamide) based dopamine conjugates were synthesized which can protect dopamine from deactivation in the human body. Since there is no satisfying kinetics description for drug release from covalent polymer-drug conjugates in the literature, dopamine release was investigated in different environments and a complete kinetical description was worked out. This study demonstrates that poly(aspartamide) is able to protect conjugated dopamine from deactivation and provide prolonged release in alkaline pH as well as in the presence of different enzymes. Furthermore, detailed kinetical descriptions were demonstrated which can be used in case of other covalent polymer-drug conjugates.

Polymeric therapeutic delivery systems for the treatment of infectious diseases

Infectious diseases caused by germs, parasites, fungi, virus and bacteria are one of the leading causes of death worldwide. Polymeric therapeutics are nanomedicines that offer several advantages making them useful for the treatment of infectious diseases such as targeted drug release mechanism, ability to maintain the drug concentration within a therapeutic window for a desired duration, biocompatibility with low immunogenicity and reduced drug toxicity resulting in enhanced therapeutic efficacy of the incorporated drug. Although polymeric therapeutics have been evaluated for the treatment of infectious diseases in vitro and in vivo with improved therapeutic efficacy, most treatments for infectious disease have not been evaluated using polymeric therapeutics. This review will focus on the applications of polymeric therapeutics for the treatment of infectious diseases (preclinical studies and clinical trials), with particular focus on parasitic and viral infections.

Layered Double Hydroxide-Based Functional Nanohybrids as Controlled Release Carriers of Pharmaceutically Active Ingredients

The chemical stability, degradation and penetration ability of pharmaceutically active ingredients in topical formulations are the greatest challenges because of problems with the protection of actives for long times and with delivery. Therefore, the development of unique and efficient substrate material is vital for their protection and controlled drug release. Layered double hydroxides (LDHs) known as hydrotalcite like compounds possess positive charges due to isomorphic substitutions, which are counterbalanced by hydrated exchangeable anions located in the interlayer region. Some of the active ingredient molecules can be intercalated into the inner region of the LDHs through ionic bonding, hydrogen bonding or van der Waals interaction to form nanohybrids, which are more potent for their protection and controlled-release. This account focuses on our recent research efforts and key scientific and technical challenges in the development of LDH based nanohybrids for commercial use in advanced controlled release carriers of active ingredients in topical formulations.