Production of Cell-Penetrating Peptides in Escherichia coli Using an Intein-Mediated System

Cell-Penetrating Peptides: A Powerful Tool for Targeted Drug Delivery

The cellular membrane hinders the effective delivery of therapeutics to targeted sites. Cellpenetrating peptide (CPP) is one of the best options for rapidly internalizing across the cellular membrane. CPPs have recently attracted lots of attention because of their excellent transduction efficiency and low cytotoxicity. The CPP-cargo complex is an effective and efficient method of delivering several chemotherapeutic agents used to treat various diseases. Additionally, CPP has become another strategy to overcome some of the current therapeutic agents' limitations. However, no CPP complex is approved by the US FDA because of its limitations and issues. In this review, we mainly discuss the cellpenetrating peptide as the delivery vehicle, the cellular uptake mechanism of CPPs, their design, and some strategies to synthesize the CPP complex via some linkers such as disulfide bond, oxime, etc. Here, we also discuss the recent status of CPPs in the market.

Nanoformulations targeting immune cells for cancer therapy: mRNA therapeutics

The approved worldwide use of two messenger RNA (mRNA) vaccines (BNT162b2 and mRNA-1273) in late 2020 has proven the remarkable success of mRNA therapeutics together with lipid nanoformulation technology in protecting people against coronaviruses during COVID-19 pandemic. This unprecedented and exciting dual strategy with nanoformulations and mRNA therapeutics in play is believed to be a promising paradigm in targeted cancer immunotherapy in future. Recent advances in nanoformulation technologies play a prominent role in adapting mRNA platform in cancer treatment. In this review, we introduce the biologic principles and advancements of mRNA technology, and chemistry fundamentals of intriguing mRNA delivery nanoformulations. We discuss the latest promising nano-mRNA therapeutics for enhanced cancer immunotherapy by modulation of targeted specific subtypes of immune cells, such as dendritic cells (DCs) at peripheral lymphoid organs for initiating mRNA cancer vaccine-mediated antigen specific immunotherapy, and DCs, natural killer (NK) cells, cytotoxic T cells, or multiple immunosuppressive immune cells at tumor microenvironment (TME) for reversing immune evasion. We highlight the clinical progress of advanced nano-mRNA therapeutics in targeted cancer therapy and provide our perspectives on future directions of this transformative integrated technology toward clinical implementation.

Purification and partial biochemical characterization of recombinant lactate dehydrogenase 1 (LDH-1) of the white shrimp Litopenaeus vannamei

Lactate dehydrogenase (LDH) is a key enzyme to produce energy during hypoxia by anaerobic glycolysis. In the white shrimp Litopenaeus vannamei, two protein subunits (LDH-1 and LDH-2) were previously identified, deduced from two different transcripts that come from the same LDH gene by processing via mutually exclusive alternative splicing. LDH-1 contains exon five and LDH-2 contains exon six and the two proteins differ only in 15 amino acid residues. Both subunits were independently cloned and overexpressed in E. coli as a fusion protein containing a chitin binding domain. Previously, recombinant LDH-2 was successfully purified and characterized, but LDH-1 was insoluble and aggregated forming inclusion bodies. We report the production of soluble LDH-1 by testing different pHs in the buffers used to lyse the bacterial cells before the purification step and the characterization of the purified protein to show that the cDNA indeed codes for a functional and active protein. The recombinant native protein is a homotetramer of approximately 140 kDa composed by 36 kDa subunits and has higher affinity for pyruvate than for lactate. LDH-1 has an optimum pH of 7.5 and is stable between pH 8.0 and 9.0; pH data analysis showed two pKa values of 6.1 ± 0.15 and 8.8 ± 0.15 suggesting a histidine and asparagine, respectively, involved in the active site. The enzyme optimal temperature was 44 °C and it was stable between 20 and 60 °C. LDH-1 was slightly activated by NaCl, KCl and MgCl₂ and fully inhibited by ZnCl₂.

Overview of Fusion Tags for Recombinant Proteins

Virtually all recombinant proteins are now prepared using fusion domains also known as "tags". The use of tags helps to solve some serious problems: to simplify procedures of protein isolation, to increase expression and solubility of the desired protein, to simplify protein refolding and increase its efficiency, and to prevent proteolysis. In this review, advantages and disadvantages of such fusion tags are analyzed and data on both well-known and new tags are generalized. The authors own data are also presented.

Strategies to stabilize cell penetrating peptides for in vivo applications

In the era of biomedicines and engineered carrier systems, cell penetrating peptides (CPPs) have been established as a promising tool for therapeutic application. Likewise, other therapeutic peptides, successful in vivo application of CPPs will strongly depend on peptide stability, the bottleneck for this type of biodegradable molecules. In this review, the authors describe the current knowledge of the in vivo degradation for known CPPs and the different strategies available to provide a higher resistance to metabolic degradation while preserving cell penetration efficiency. Peptide stability can be improved by different means, either modifying the structure to make it unrecognizable to proteases, or preventing access of proteolytic enzymes by applying conformation restriction or shielding strategies.