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Nanoparticles-based multivalent antigen display has the capability of mimicking natural virus infection characteristics, making it useful for eliciting potent long-lasting immune response. Several vaccines are developed against global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However these subunit vaccines use mammalian expression system, hence mass production with rapid pace is a bigger challenge. In contrast E. coli based subunit vaccine production circumvents these limitations. The objective of the present investigation was to develop nanoparticle vaccine with multivalent display of receptor binding domain (RBD) of SARS-CoV-2 expressed in E. coli. Results showed that RBD entrapped PLA (Poly lactic acid) nanoparticle in combination with aluminum hydroxide elicited 9-fold higher immune responses as compared to RBD adsorbed aluminum hydroxide, a common adjuvant used for human immunization. It was interesting to note that RBD entrapped PLA nanoparticle with aluminum hydroxide not only generated robust and long-lasting antibody response but also provided Th1 and Th2 balanced immune response. Moreover, challenge with 1 µg of RBD alone was able to generate secondary antibody response, suggesting that immunization with RBD-PLA nanoparticles has the ability to elicit memory antibody against RBD. Plaque assay revealed that the antibody generated using the polymeric formulation was able to neutralize SARS-CoV-2. The RBD entrapped PLA nanoparticles blended with aluminum hydroxide thus has potential to develop asa subunit vaccine against COVID-19.

Expression of heterologous proteins in E. coli often leads to the formation of protein aggregates known as inclusion bodies (IBs). Inclusion body aggregates pose a major hurdle in the recovery of bioactive proteins from E. coli. Usage of strong denaturing buffers for solubilization of bacterial IBs results in poor recovery of bioactive protein. Structure-function understanding of IBs in the last two decades have led to the development of several mild solubilization buffers, which improve the recovery of bioactive from IBs. Recently, combinatorial mild solubilization methods have paved the way for solubilization of wide range of inclusion bodies with appreciable refolding yield. Here, we describe a simple protocol for solubilization and refolding of an inclusion body protein with appreciable recovery.

Formation of protein aggregates as inclusion bodies (IBs) still poses a major hurdle in the recovery of bioactive proteins from E. coli. Despite the development of many mild solubilization buffers in last two decades, high-throughput recovery of functional protein from wide range of IBs is still a challenge at an academic and industrial scale. Herein, a novel formulation for improved recovery of bioactive protein from variety of bacterial IBs is developed. This novel formulation is comprised of 20% trifluoroethanol, 20% n-propanol and 2 M urea at pH 12.5 which disrupts the major dominant forces involved in protein aggregation. An extensive comparative study of novel formulation conducted on different IBs demonstrates its high solubilization and refolding efficiency. The overall yield of bioactive protein from human growth hormone expressed as bacterial IBs is reported to be around 50%. This is attributed to the capability of novel formulation to disrupt the tertiary structure of the protein while protecting the secondary structure of the protein, thereby reducing the formation of soluble aggregates during refolding. Thus, the formulation can eliminate the need of screening and optimizing various solubilization formulation and will improve the efficiency of recovering bioactive protein from variety of IB aggregates.

Recombinant proteins expressed as bacterial inclusion bodies (IBs) are now receiving tremendous attention for many diverse applications in the areas of industrial and medical biotechnology. Understanding the structure–function relationship of protein in IBs has recently created new possibilities in developing innovative isolation, solubilization, refolding, and purification processes for high-throughput recovery of bioactive protein from bacterial IBs. This opinion article describes the advantages, disadvantages, and major challenges presently associated with each of the processing steps. Finally, we conclude with the possible solutions for each operational step and the future direction of the basic and translational research to achieve maximum benefit from IB aggregates.

In recent years, a great deal of attention has been given towards re-purposing and re-innovating the potential drugs. In this regard, dihydroartemisinin (DHA) has been reported to demonstrate anti-proliferative effects on various cancerous cells viz. breast, liver and lung. However, it is associated with some limitations, such as low bioavailability which is hampered by its poor aqueous solubility and its rapid metabolism in systemic circulation. Therefore, in order to overcome these limitations, we synthesized a novel hyaluronic acid-dihydroartemisinin conjugate in which the hydroxyl group of DHA was covalently linked to carboxylic group of hyaluronic acid (HA). The conjugate was successfully characterized using 1H NMR, Fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC). The synthesized conjugate self-assembled into nanoparticles in aqueous solution. The developed nanoparticles were characterized for their average size, zeta potential, Transmission Electron Microscopy (TEM), X-ray Powder Diffraction (XRD) and loading efficiency. The nanoparticles were cytotoxic to lung cancer (A549) cell line which was determined using CCK-8 cell viability assay. This was further supported by Annexin-V-FITC-Propidium iodide apoptosis assay, reactive oxygen species (ROS) production and mitochondrial membrane potential (MMP) loss. Conclusively, present findings demonstrate hyaluronic acid conjugates can be used to improve the therapeutic outcomes of anticancer drugs.