Harnessing the Therapeutic Potential of Biomacromolecules through Intracellular Delivery of Nucleic Acids, Peptides, and Proteins

Fusogenic Lipid Nanovesicle for Biomacromolecular Delivery

Although biomacromolecules are promising cytosolic drugs which have attracted tremendous attention, the major obstacles were the cellular membrane hindering the entrance and the endosome entrapment inducing biomacromolecule degradation. How to avoid those limitations to realize directly cytosolic delivery was still a challenge. Here, we prepared oligoarginine modified lipid to assemble a nanovesicle for biomacromolecules delivery, including mRNA (mRNA) and proteins which could be directly delivered into the cytoplasm of dendritic cells through subendocytosis-mediated membrane fusion. We named this membrane fusion lipid nanovesicle as MF-LNV. The mRNA loaded MF-LNV as nanovaccines showed efficient antigen expression to elicit robust immuno responses for cancer therapy. What's more, the antigen protein loaded MF-LNV as nanovaccines elicits much stronger CD8+ T cell specific responses than lipid nanoparticles through normal uptake pathways. This MF-LNV represented a refreshing strategy for intracellular delivery of the biomacromolecule.

Subcellular targeting strategies for protein and peptide delivery

Cytosolic delivery of proteins and peptides provides opportunities for effective disease treatment, as they can specifically modulate intracellular processes. However, most of protein-based therapeutics only have extracellular targets and are cell-membrane impermeable due to relatively large size and hydrophilicity. The use of organelle-targeting strategy offers great potential to overcome extracellular and cell membrane barriers, and enables localization of protein and peptide therapeutics in the organelles. Although progresses have been made in the recent years, organelle-targeted protein and peptide delivery is still challenging and under exploration. We reviewed recent advances in subcellular targeted delivery of proteins/peptides with a focus on targeting mechanisms and strategies, and highlight recent examples of active and passive organelle-specific protein and peptide delivery systems. This emerging platform could open a new avenue to develop more effective protein and peptide therapeutics.

High-Throughput Screening of Surface Engineered Cyanine Nanodots for Active Transport of Therapeutic Antibodies into Solid Tumor

The successful delivery of therapeutic biomacromolecules into solid tumor holds great challenge due to their high resistance to penetrate through the complex tumor microenvironments. Here, active-transporting nanoparticles are harnessed to efficiently deliver biomacromolecular drugs into solid tumors through cell transcytosis. A series of molecularly precise cyanine 5-cored polylysine G5 dendrimers (Cy5 nanodots) with different peripheral amino acids (G5-AA) is prepared. The capability of these positively charged nanodots to induce cell endocytosis, exocytosis, and transcytosis is evaluated via fluorescence-based high-throughput screen. The optimized nanodots (G5-R) are conjugated with αPD-L1 (a therapeutic monoclonal antibody binding to programmed-death ligand 1) (αPD-L1-G5-R) to demonstrate the nanoparticle-mediated tumor active transport. The αPD-L1-G5-R can greatly enhance the tumor-penetration capability through adsorption-mediated transcytosis (AMT). The effectiveness of αPD-L1-G5-R is tested in treating mice bearing partially resected CT26 tumors, mimicking the local immunotherapy of residual tumors post-surgery in clinic. The αPD-L1-G5-R embedded in fibrin gel can efficiently mediate tumor cell transcytosis, and deliver αPD-L1 throughout the tumor, thereby enhancing immune checkpoint blockade, reducing tumor recurrence, and significantly prolonging the survival time. The active-transporting nanodots are promising platforms for efficient tumor delivery of therapeutic biomacromolecules.

Intracellular Delivery of Functional Proteins with DNA-Protein Nanogels-Lipids Complex

Using functional proteins for therapeutic purposes due to their high selectivity and/or catalytic properties can enable the control of various cellular processes; however, the transport of active proteins inside living cells remains a major challenge. In contrast, intracellular delivery of nucleic acids has become a routine method for a number of applications in gene therapy, genome editing, or immunization. Here we report a functionalizable platform constituting of DNA-protein nanogel carriers cross-linked through streptavidin-biotin or streptactin-biotin interactions and demonstrate its applicability for intracellular delivery of active proteins. We show that the nanogels can be loaded with proteins bearing either biotin, streptavidin, or strep-tag, and the resulting functionalized nanogels can be delivered into living cells after complexation with cationic lipid vectors. We use this approach for delivery of alkaline phosphatase enzyme, which is shown to keep its catalytic activity after internalization by mouse melanoma B16 cells, as demonstrated by the DDAO-phosphate assay. The resulting functionalized nanogels have dimensions on the order of 100 nm, contain around 100 enzyme molecules, and are shown to be transfectable at low lipid concentrations (charge ratio R± = 0.75). This ensures the low toxicity of our system, which in combination with high local enzyme concentration (∼100 μM) underlines potential interest of this nanoplatform for biomedical applications.

Organ/Cell-Selective Intracellular Delivery of Biologics via N-Acetylated Galactosamine-Functionalized Polydisulfide Conjugates

Biologics, including proteins and antisense oligonucleotides (ASOs), face significant challenges when it comes to achieving intracellular delivery within specific organs or cells through systemic administrations. In this study, we present a novel approach for delivering proteins and ASOs to liver cells, both in vitro and in vivo, using conjugates that tether N-acetylated galactosamine (GalNAc)-functionalized, cell-penetrating polydisulfides (PDSs). The method involves the thiol-bearing cargo-mediated ring-opening polymerization of GalNAc-functionalized lipoamide monomers through the so-called aggregation-induced polymerization, leading to the formation of site-specific protein/ASO-PDS conjugates with narrow dispersity. The hepatocyte-selective intracellular delivery of the conjugates arises from a combination of factors, including first GalNAc binding with ASGPR receptors on liver cells, leading to cell immobilization, and the subsequent thiol-disulfide exchange occurring on the cell surface, promoting internalization. Our findings emphasize the critical role of the close proximity of the PDS backbone to the cell surface, as it governs the success of thiol-disulfide exchange and, consequently, cell penetration. These conjugates hold tremendous potential in overcoming the various biological barriers encountered during systemic and cell-specific delivery of biomacromolecular cargos, opening up new avenues for the diagnosis and treatment of a range of liver-targeting diseases.

Hydroxyl-rich branched polycations for nucleic acid delivery

Recently, nucleic acid delivery has become an amazing route for the treatment of various malignant diseases, and polycationic vectors are attracting more and more attention among gene vectors. However, conventional polycationic vectors still face many obstacles in nucleic acid delivery, such as significant cytotoxicity, high protein absorption behavior, and unsatisfactory blood compatibility caused by a high positive charge density. To solve these problems, the fabrication of hydroxyl-rich branched polycationic vectors has been proposed. For the synthesis of hydroxyl-rich branched polycations, a one-pot method is considered as the preferred method due to its simple preparation process. In this review, typical one-pot methods for fabricating hydroxyl-rich polycations are presented. In particular, amine-epoxide ring-opening polymerization as a novel approach is mainly introduced. In addition, various therapeutic scenarios of hydroxyl-rich branched polycations via one-pot fabrication are also generalized. We believe that this review will motivate the optimized design of hydroxyl-rich branched polycations for potential nucleic acid delivery and their bio-applications.

Chemical Modification of Cytochrome C for Acid-Responsive Intracellular Apoptotic Protein Delivery for Cancer Eradication

Delivering bioactive proteins into cells without carriers presents significant challenges in biomedical applications due to limited cell membrane permeability and the need for targeted delivery. Here, we introduce a novel carrier-free method that addresses these challenges by chemically modifying proteins with an acid-responsive cell-penetrating peptide (CPP) for selective intracellular delivery within tumours. Cytochrome C, a protein known for inducing apoptosis, served as a model for intracellular delivery of therapeutic proteins for cancer treatment. The CPP was protected with 2,3-dimethyl maleic anhydride (DMA) and chemically conjugated onto the protein surface, creating an acid-responsive protein delivery system. In the acidic tumour microenvironment, DMA deprotects and exposes the positively charged CPP, enabling membrane penetration. Both in vitro and in vivo assays validated the pH-dependent shielding mechanism, demonstrating the modified cytochrome C could induce apoptosis in cancer cells in a pH-selective manner. These findings provide a promising new approach for carrier-free and tumour-targeted intracellular delivery of therapeutic proteins for a wide range of potential applications.

A high-throughput microfluidic mechanoporation platform to enable intracellular delivery of cyclic peptides in cell-based assays

Cyclic peptides are poised to target historically difficult to drug intracellular protein-protein interactions, however, their general cell impermeability poses a challenge for characterizing function. Recent advances in microfluidics have enabled permeabilization of the cytoplasmic membrane by physical cell deformation (i.e., mechanoporation), resulting in intracellular delivery of impermeable macromolecules in vector- and electrophoretic-free approaches. However, the number of payloads (e.g., peptides) and/or concentrations delivered via microfluidic mechanoporation is limited by having to pre-mix cells and payloads, a manually intensive process. In this work, we show that cells are momentarily permeable (t 1/2 = 1.1-2.8 min) after microfluidic vortex shedding (μVS) and that lower molecular weight macromolecules can be cytosolically delivered upon immediate exposure after cells are processed/permeabilized. To increase the ability to screen peptides, we built a system, dispensing-microfluidic vortex shedding (DμVS), that integrates a μVS chip with inline microplate-based dispensing. To do so, we synced an electronic pressure regulator, flow sensor, on/off dispense valve, and an x-y motion platform in a software-driven feedback loop. Using this system, we were able to deliver low microliter-scale volumes of transiently mechanoporated cells to hundreds of wells on microtiter plates in just several minutes (e.g., 96-well plate filled in <2.5 min). We validated the delivery of an impermeable peptide directed at MDM2, a negative regulator of the tumor suppressor p53, using a click chemistry- and NanoBRET-based cell permeability assay in 96-well format, with robust delivery across the full plate. Furthermore, we demonstrated that DμVS could be used to identify functional, low micromolar, cellular activity of otherwise cell-inactive MDM2-binding peptides using a p53 reporter cell assay in 96- and 384-well format. Overall, DμVS can be combined with downstream cell assays to investigate intracellular target engagement in a high-throughput manner, both for improving structure-activity relationship efforts and for early proof-of-biology of non-optimized peptide (or potentially other macromolecular) tools.

Intrathecal delivery of Macromolecules: Clinical status and emerging technologies

The proximity and association of cerebrospinal fluid (CSF) and the intrathecal (IT) space with deep targets in the central nervous system (CNS) parenchyma makes IT injection an attractive route of administration for brain drug delivery. However, the extent to which intrathecally administered macromolecules are effective in treating neurological diseases is a question of both clinical debate and technological interest. We present the biological, chemical, and physical properties of the intrathecal space that are relevant to drug absorption, distribution, metabolism, and elimination from CSF. We then analyze the evolution of IT drug delivery in clinical trials over the last 20 years. Our analysis revealed that the percentage of clinical trials assessing IT delivery for the delivery of biologics (i.e., macromolecules, cells) for treatment of chronic conditions (e.g., neurodegeneration, cancer, and metabolic diseases) has steadily increased. Clinical trials exploring cell or macromolecular delivery within the IT space have not evaluated engineering technologies, such as depots, particles, or other delivery systems. Recent pre-clinical studies have evaluated IT macromolecule delivery in small animals, postulating that delivery efficacy can be assisted by external medical devices, micro- or nanoparticles, bulk biomaterials, and viral vectors. Further studies are necessary to evaluate the extent to which engineering technologies and IT administration improve CNS targeting and therapeutic outcome.

Intracellular delivery of therapeutic proteins. New advancements and future directions

Achieving the full potential of therapeutic proteins to access and target intracellular receptors will have enormous benefits in advancing human health and fighting disease. Existing strategies for intracellular protein delivery, such as chemical modification and nanocarrier-based protein delivery approaches, have shown promise but with limited efficiency and safety concerns. The development of more effective and versatile delivery tools is crucial for the safe and effective use of protein drugs. Nanosystems that can trigger endocytosis and endosomal disruption, or directly deliver proteins into the cytosol, are essential for successful therapeutic effects. This article aims to provide a brief overview of the current methods for intracellular protein delivery to mammalian cells, highlighting current challenges, new developments, and future research opportunities.

Dose-Dependent Nuclear Delivery and Transcriptional Repression with a Cell-Penetrant MeCP2

The vast majority of biologic-based therapeutics operate within serum, on the cell surface, or within endocytic vesicles, in large part because proteins and nucleic acids fail to efficiently cross cell or endosomal membranes. The impact of biologic-based therapeutics would expand exponentially if proteins and nucleic acids could reliably evade endosomal degradation, escape endosomal vesicles, and remain functional. Using the cell-permeant mini-protein ZF5.3, here we report the efficient nuclear delivery of functional Methyl-CpG-binding-protein 2 (MeCP2), a transcriptional regulator whose mutation causes Rett syndrome (RTT). We report that ZF-tMeCP2, a conjugate of ZF5.3 and MeCP2(Δaa13-71, 313-484), binds DNA in a methylation-dependent manner in vitro, and reaches the nucleus of model cell lines intact to achieve an average concentration of 700 nM. When delivered to live cells, ZF-tMeCP2 engages the NCoR/SMRT corepressor complex, selectively represses transcription from methylated promoters, and colocalizes with heterochromatin in mouse primary cortical neurons. We also report that efficient nuclear delivery of ZF-tMeCP2 relies on an endosomal escape portal provided by HOPS-dependent endosomal fusion. The Tat conjugate of MeCP2 (Tat-tMeCP2), evaluated for comparison, is degraded within the nucleus, is not selective for methylated promoters, and trafficks in a HOPS-independent manner. These results support the feasibility of a HOPS-dependent portal for delivering functional macromolecules to the cell interior using the cell-penetrant mini-protein ZF5.3. Such a strategy could broaden the impact of multiple families of biologic-based therapeutics.

Delivery of Therapeutic Biopolymers Employing Silica-Based Nanosystems

The use of nanoparticles is crucial for the development of a new generation of nanodevices for clinical applications. Silica-based nanoparticles can be tailored with a wide range of functional biopolymers with unique physicochemical properties thus providing several advantages: (1) limitation of interparticle interaction, (2) preservation of cargo and particle integrity, (3) reduction of immune response, (4) additional therapeutic effects and (5) cell targeting. Therefore, the engineering of advanced functional coatings is of utmost importance to enhance the biocompatibility of existing biomaterials. Herein we will focus on the most recent advances reported on the delivery and therapeutic use of silica-based nanoparticles containing biopolymers (proteins, nucleotides, and polysaccharides) with proven biological effects.

Are We There Yet? Intracellular Sensing with Luminescent Nanoparticles and FRET

Combinations of luminescent nanoparticles (LNPs) and Förster resonance energy transfer (FRET) offer properties and features that are advantageous for sensing of biomolecular targets and activity. Despite a multitude of designs for LNP-FRET sensors, intracellular sensing applications are underdeveloped. We introduce readers to this field, summarize essential concepts, meta-analyze the literature, and offer a perspective on the bottleneck in LNP-FRET sensor development.

Development of a Lysine-Based Poly(ester amide) Library with High Biosafety and a Finely Tunable Structure for Spatiotemporal-Controlled Protein Delivery

With the fast growth of protein therapeutics, efficient, precise, and universal delivery platforms are highly required. However, very few reports have discussed the progress of precisely spatiotemporal-controlled protein delivery. Therefore, a mini library of well-designed amino acid-based poly(ester amide)s derived from lysine (Lys-aaPEAs) has been developed. Lys-aaPEAs can interact with and encapsulate proteins into nanocomplexes via electrostatic interactions. The chemical structure of Lys-aaPEAs can be finely tuned by changing the type and molar ratio of the monomers. Studies of structure-function relationships reveal that the carbon chain length of diacid/diol segments, hydrophilicity, and electrical properties affect the polymer-protein interaction, cell-material interaction, and, therefore, the outcome of protein delivery. By modulating the structures of Lys-aaPEAs, the delivery systems could present customized physiochemical and biological properties and perform time- and space-specific protein release and delivery without causing any systematic toxicity. The screened systems exhibited prolonged hypoglycemic activity and superior biosafety in vivo, using insulin as a model protein and a mouse model bearing type 1 diabetes mellitus (T1DM). This work establishes a novel lysine-based polymer platform for spatiotemporal-controlled protein delivery and offers a paradigm of precise structure-function controllability for designing the next generation of polymers.

Bridging polymer chemistry and cryobiology

Polymers, especially charged polymers, are the key to a sustainable future, as they have the capability to act as alternatives to plastics, reduce the impact of global warming, and offer solutions to global environmental pollution problems. Biomaterial polymers have proven to be incredibly effective in a multitude of applications, including clinical applications. In the fields of cryobiology and cryopreservation, polymers have emerged as credible alternatives to small molecules and other compounds, yielding excellent results. This review outlines the results of research in the areas of polymer chemistry and cryobiology, which have not been discussed together previously. Herein, we explain how recent polymer research has enabled the development of polymeric cryoprotectants with novel mechanisms and the development of novel methods for the intracellular delivery of substances, such as drugs, using a cryobiological technique called the freeze-concentration effect. Our findings indicate that interdisciplinary collaboration between cryobiologists and polymer chemists has led to exciting developments that will further cell biology and medical research.

The Journey of 1-Keto-1,2,3,4-Tetrahydrocarbazole Based Fluorophores: From Inception to Implementation

Carbazole is a unique template associated with several biological activities. It is due to the diverse and versatile biological properties of carbazole derivatives that they are of immense interest to the research community. 1-keto-1,2,3,4-tetrahydrocarbazoles are important synthetic intermediates to obtain carbazole derivatives. Several members of this family emit fluorescence on photoexcitation. In the context of biochemical and biophysical research, designing and characterising small molecule environment sensitive fluorophores is extremely significant. This article aims to be a state of the art review with synthetic and photophysical details of a variety of fluorophores based on 1-keto-1,2,3,4-tetrahydrocarbazole skeleton.