A hybrid HPV capsid protein L1 with giant Mo-containing polyoxometalate improves the stability of virus-like particles and the anti-tumor effect of [Mo154]

We report a bio-inorganic hybrid system, [Mo154]@VLPs, constructed from the virus-like particles (VLPs) of the HPV capsid protein L1 and a giant disc-shaped, molybdenum-containing polyoxometalate of [Mo154]. The hybrid was purified by CsCl gradient centrifugation and further validated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), dynamic light scattering (DLS) and transmission electron microscopy (TEM). An assembly with [Mo154] improved the tolerance of VLPs to pH, temperature, and storage time, thereby defining an opportunity to reduce the cost of HPV vaccines. Moreover, the ability of [Mo154] to kill cancer cells was improved by 6% after being encapsulated inside the VLPs, which is mainly attributed to the enhanced biocompatibility of [Mo154]. The irradiation of both [Mo154] and [Mo154]@VLPs with an infrared light of 808 nm further enhanced their ability to destroy cancer cells by 3- and 2-fold, respectively, confirming that [Mo154] is an effective anti-tumor photo-thermal agent. Therefore, the successful hybrid of L1-p and [Mo154] improves the stability of VLPs and simultaneously paves the way to enhance the anti-tumor ability of [Mo154] and further extends its application prospects as a future anti-tumor drug.

Co-assembly of HPV capsid proteins and aggregation-induced emission fluorogens for improved cell imaging

In order to improve the cell-imaging ability, and particularly, to extend the bio-application of AIEgen, human papillomavirus (HPV) capsid protein L1 was assembled with the complex of DNA and aggregation-induced emission fluorogen 9,10-distyrylhydrazine (DSAI), where the virus-like particles (VLPs) of HPV encapsulate the complex via electrostatic interaction. The co-assembled nanoparticles, DSAI-DNA@VLPs, showed homogeneous size (∼53 nm), enhanced fluorescence (8 × 2.5-fold), considerable stability (anti-DNase digestion), improved biocompatibility and commendable protection for the DSAI-DNA complex, ensuring virtual brighter imaging in live cells, both for HeLa and normal 293T cell lines.

Hybrid Assembly toward Enhanced Thermal Stability of Virus-like Particles and Antibacterial Activity of Polyoxometalates

In an effort to improve both the stability of virus-like particles (VLPs) and the medical activity of polyoxometalates (POMs), a new hybrid assembly system between human papillomavirus (HPV) capsid protein L1 and a europium-containing POM (EuW₁₀) has been constructed, for the first time, via the electrostatic interactions between them. The co-assembly of EuW₁₀ and HPV 16 L1-pentamer (L1-p) in buffer solution resulted in the encapsulation of POMs in the cavity of VLPs, which was further confirmed by cesium chloride (CsCl) gradient ultracentrifugation, SDS-PAGE, dynamic light scattering, and transmission electron microscopy, whereas the post-assembly of EuW₁₀ with the as-prepared VLPs leads to the adsorption of POMs only on the external surface of particles, and both cases improved the thermal and storage stabilities of VLPs obviously. Particularly, the encapsulation of POMs in VLPs largely improved the antibacterial activity of EuW₁₀, and thereby, the present study will be significant for both the stability improvement of protein vaccines and the development of POM medicine.

Cell receptor screening for human papillomavirus invasion by using a polyoxometalate-peptide assembly as a probe

The present study constructed a competitive recognition system using cell receptor screening for human papillomavirus (HPV) invasion by using the hybrid-assembly of polyoxometalates (POMs) and cationic peptides as a platform. The fine tuning both of the surface charge of POMs and peptide sequence were precisely performed to develop a luminescence switch of POMs, leading to the establishment of a ternary system to identify which types of glycosaminoglycans (GAGs) are potential cell receptors for HPV infection. In addition, the method was successfully applied to construct a hybrid-assembly with the recombined HPV 16 L1 pentamers from Escherichia coli and perform GAGs screening, which validated the system's potential for practical applications. In particular, the intrinsic mechanism for each competitive partner in the system was explained well by using isothermal titration calorimetry (ITC) and time-resolved fluorescence spectra. The present method will be helpful to extend the protocol to other systems by using peptides and POMs with similar properties, and ultimately, we hope it will promote the development of anti-viral agents.

A novel fluorescent turn-on biosensor based on QDs@GSH-GO fluorescence resonance energy transfer for sensitive glutathione S-transferase sensing and cellular imaging

A novel fluorescent turn-on biosensor based on fluorescence resonance energy transfer (FRET) from GSH functionalized Mn-doped ZnS QDs to graphene oxide (GO) was constructed to determine glutathione S-transferases (GSTs) in live cells and human urine. The QDs@GSH is adsorbed on the GO surface via hydrogen bonding interaction between the GSH on the surface of QDs@GSH and GO, and as a result, fluorescence quenching of the QDs@GSH takes place because of FRET. The FRET efficiency from QDs@GSH to GO was calculated to be 86.3%. However, in the presence of GSTs, the FRET process could be inhibited by the specific interaction between the GSH on the surface of QDs@GSH and GSTs, which would keep the QDs@GSH far away from the GO surface, leading to the recovery of the fluorescence. The proposed sensor exhibited high sensitivity, selectivity, and excellent specificity in the buffer, live cells and human urine for the detection of GSTs. Under the physiological conditions (pH 7.4), dissociation constants and the detection limit of GST and ATP6 V1F (a GST-tagged protein) were estimated to be 8.0 × 10^-9 M, 2.1 × 10^-10 M and 3.5 × 10^-9 M, 7.2 × 10^-11 M, respectively. The presented method has been successfully utilized for the determination of the GSTs in live cells and human urine without any complicated pretreatment and the recovery was in the range of 80%-90%.

Controlled Hybrid-Assembly of HPV16/18 L1 Bi VLPs in Vitro

Based on the helix4-exchanged HPV16 L1 and HPV18 L1, HPV16 L1 Bi and HPV18 L1 Bi, we have successfully realized the controlled hybrid-assembly of HPV16/18 L1 Bi VLPs (bihybrid-VLPs) in vitro. The bihybrid-VLPs were further confirmed by fluorescence resonance energy transfer (FRET) and complex-immunoprecipitation (Co-IP) assays. The ratio of 16 L1 Bi and 18 L1 Bi in bihybrid-VLPs was verified to be 3:5 based on a modified magnetic Co-IP procedure, when mixing 1 equiv pentamer in assembly buffer solution, but it changed with conditions. In addition, the bihybrid-VLPs showed identical thermal stability as that of normal VLPs, suggesting high potential in practical applications. The present study is significant because it modified one of the vital steps of virus life cycle at the stage of virus assembly, supplying a new approach not only to deepen structural insights but also a possibility to prepare stable, low-cost, bivalent antivirus vaccine. Furthermore, the controlled hybrid-assembly of bihybrid-VLPs in vitro provides suggestions for the design of effective multivalent hybrid-VLPs, being a potential to develop broad-spectrum vaccines for the prevention of infection with multiple types of HPV.

A fluorescence-enhanced inorganic probe to detect the peptide and capsid protein of human papillomavirus in vitro

A europium-substituted polyoxometalate (EuW10) could be used as a fluorescence-enhanced probe to detect the recombinant HPV L1 protein in vitro.

Peptidic inhibitors for in vitro pentamer formation of human papillomavirus capsid protein l1

A new 14 peptide, originating essentially from the helix 5 of HPV 16L1, illustrates an IC50 of 19.38 nM for the inhibition of HPV 16 L1 pentamer formation, which is highly efficient for targeting a specific protein segment. In addition, mechanism studies reveal that the length, sequence, and the folding of the peptide are critical factors for its inhibition. Particularly, the peptide shows similar inhibition against the pentamer formation of HPV 58L1, although it is designed specially for HPV 16 L1. This study opens a way for the development of high-efficiency, broad-spectrum inhibitors as a new class of anti-HPV agents, which could be extended to the treatment of other virus types.

The critical residues of helix 5 for in vitro pentamer formation and stability of the papillomavirus capsid protein, L1

The mono-site mutation of the conserved residues, ⁴⁶⁴LGR⁴⁶⁶, in the helix 5 of HPV16 L1 completely disrupted the pentamer formation.