Recent trends in protein and peptide-based biomaterials for advanced drug delivery

Abstract

Engineering protein and peptide-based materials for drug delivery applications has gained momentum due to their biochemical and biophysical properties over synthetic materials, including biocompatibility, ease of synthesis and purification, tunability, scalability, and lack of toxicity. These biomolecules have been used to develop a host of drug delivery platforms, such as peptide- and protein-drug conjugates, injectable particles, and drug depots to deliver small molecule drugs, therapeutic proteins, and nucleic acids. In this review, we discuss progress in engineering the architecture and biological functions of peptide-based biomaterials -naturally derived, chemically synthesized and recombinant- with a focus on the molecular features that modulate their structure-function relationships for drug delivery.

Keywords: Bioinspired materials; Drug delivery; Hierarchical self-assembly; Polypeptides; Recombinant proteins.

Fig. 1

List of protein-based materials discussed in this review. Created with Biorender.com

Fig. 2

A brief timeline of advances made in engineering protein-based biomaterials for controlled drug delivery.

Fig. 3

Recent advances in the engineering of the peptide-based biomaterials as delivery vehicles. Created with Biorender.com.

Fig. 4

Intrinsic design modules of a peptide amenable to precision engineering for drug delivery application. Created with Biorender.com.

Fig. 5

Synthesis procedure of SF@MnO2/ICG/DOX (SMID) nanoparticles. SMID nanoparticle acts as a multifunctional drug delivery platform for in vivo MR/fluorescence imaging-assisted tri-modal therapy of cancer. Adapted with permission from [83].

Fig. 6

Conjugation of the cyclic pentapeptide cRGDfk and the photodynamic agent Chlorin e6 (Ce6) to SF was achieved using a simple acid-amine coupling reaction and the resulting conjugate was doped with 5-fluorouracil (5-FU) using genipin peptide as a crosslinker. Adapted with permission from [84].

Fig. 7

Dual stimulus responsiveness of keratin-based drug loaded nanoparticles (KDNPs). (A) Schematic of nanoparticle fabrication and GSH- or pH- stimulated drug release (B) An acidic environment shifts the size and zeta potential of KDNPs and accelerates the release of entrapped DOX (C) The presence of GSH shifts the size and zeta potential of KDNPs and accelerates the release of entrapped DOX. Adapted with permission from [105].

Fig. 8

Disulfide shuffling to modulate drug release from keratin hydrogels. (A) Schematic of gelation by the disulfide shuffling strategy. Crosslinking density and thus microstructure, mechanical strength, and degradation can be tuned with this method (B,C) Hydrogel degradation and ciprofloxacin release in PBS demonstrate that greater crosslinking, represented by a greater number of Cys residues, slows degradation and release. (D,E) Hydrogel degradation and DOX release in the presence of GSH demonstrates the redox responsiveness of these hydrogels. Adapted with permission from [117].

Fig. 9

Ribbon diagram of the three-dimensional structure of human serum albumin (A). Schematic of the in vivo thiol-maleimide conjugation reaction (B). Chemical structure of DOX-EMCH/Aldoxorubicin (C). Adapted with permission from [140] (A) and [144] (B).

Fig. 10

Design of doxorubicin(DOX)-conjugated albumin-binding nanoparticles. DOX was conjugated via a pH-sensitive hydrazone linker. (B) Albumin-binding properties of ABDN-CP-DOX and ABDH-CP-DOX were qualitatively demonstrated using native PAGE. (C) Cryo-TEM images of ABDN-CP-DOX (I) and CP-DOX (II) micelles. (D) Isothermal titration calorimetry of ABDN-CP-DOX and ABDH-CP-DOX micelles with MSA. The solid red line represents the best fit of the binding isotherm. (E, F) Pharmacokinetics of ABD-decorated nanoparticles in murine (E) and canine (F) models. Adapted with permission from [126]. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 11

(A) Synthetic scheme of ABD–DOX. Elastin-like polypeptide (ELP) was used as a purification tag and removed following drug conjugation using sortase A. Inclusion of the KEKE peptide at the N-terminus disrupted micellar self-assembly upon DOX conjugation and enabled the subsequent sortase A cleavage of ELP from the ABD–DOX conjugate. (B) Synthetic scheme of albumin−polymer−drug conjugates. Drug-containing monomer (drug: panobinostat, dark blue) was copolymerized with HPMA using RAFT agents, which allow one-step conjugation of albumin. Adapted with permission from [59] (A) and [172] (B). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 12

CBD–IL-12 binds to collagen with high affinity without compromising functionality. (A) Schematic of the fusion sites of the von Willebrand factor A3 CBD to the mouse p35 and p40 subunits via a (GGGS)2 linker. (B) Dose–response of phosphorylated STAT4 to IL-12 and CBD–IL-12 in preactivated primary mouse CD8+ T cells. EC₅₀, half-maximum effective concentration; MFI, mean fluorescence intensity. (C, D) Binding of CBD–IL-12 to collagen I (C) and collagen III (D) as measured by SPR. The curves represent the specific responses (in resonance units (RU)) to CBD–IL-12. (E, F) Affinity of bare IL-12 (E) or CBD–IL-12 (F) to human melanoma cryosections was imaged using fluorescence microscopy. Scale bars, 100 μm. Adapted with permission from [237].

Fig. 13

(A) Amino acid sequence of synthetic collagen-like peptide CPII. Distinct domain structure of collagen triads is shown. (B) Proposed triple-helical wheel diagram of CPII. (C) Side view of higher-order assembly of a CPII homotrimer illustrating the proposed interhelical electrostatic interactions to yield triple-helical protomers. (D) Schematic representation of CPII fibrillogenesis. Adapted with permission from [251].

Fig. 14

Chemical conjugation of ELP and CLP using a Cu-mediated click reaction. (B) Proposed assembly and disassembly behavior of the CLP-ELP vesicle. (C) Conjugation and two-step assembly mechanism of the CLP-PDEGMEMA conjugate. Adapted with permission from [265,266].

Fig. 15

(A) Three-step preparation of gelatin nanoparticles coated with pH-sensitive polymer. (B) Schematic presentation of the synthesis of RB-GNP. Adapted with permission from [286] (A) and [290] (B).

Fig. 16

Lower critical solution temperature behavior of elastin-like polypeptides (ELPs). (A, B) At temperatures below the transition temperature (T_t), water molecules order themselves along the ELP chain such that the ELP remains soluble and appears optically clear. At temperatures above the transition temperature, water is expelled from the polymer, and the polypeptide chain aggregates, leading to a turbid suspension. C) The T_t can be determined from the temperature dependent optical turbidity and increases with guest residue hydrophobicity, molecular weight, and concentration. Adapted with permission from [316] (A & B) and [321].

Fig. 17

Design and efficacy of zwitterionic polypeptides (ZIPPs). (A) ZIPPs are homopolymers comprised of repeating monomers of the pentapeptide Val-Pro-X1-X2-Gly, where X1 and X2 are cationic and anionic residues, respectively. (B) ZIPPs have a higher plasma concentration than length- and MW-matched ELPs after intravenous injection (C, D) A ZIPP fusion to the antidiabetic peptide GLP1 resulted in bettr blood-glucose control than a MW matched ELP. Adapted with permission from [335].

Fig. 18

Design and efficacy of CP-DOX nanoparticles. (A) ELPs are conjugated to DOX at Cys residues via a heterobifunctional linker. (B) CP nanoparticles self-assemble to entrap hydrophobic DOX in the core and display the hydrophilic polypeptide on the corona. (C) DOX release from CP-DOX is pH-dependent. (D, E) CP-DOX formulation promotes DOX accumulation in the tumor while reducing its presence in heart tissue. (F) A single injection of CP-DOX outperforms free DOX in reducing tumor volume. Adapted with permission from [354].

Fig. 19

Design and efficacy of an optimized subcutaneous depot of GLP1-ELP. A single injection of the ELP fusion maintained blood glucose control in (A) diet-induced obese mice, (B) ob/ob mice, and (C) db/db mice for up to 10 days. (D) Circulating levels of the GLP1-ELP fusion were detectable for up to 21 days in cynomolgus monkeys. (E) The enhanced pharmacokinetics of GLP1 are attributed to the increased residence time of depot-forming GLP1-ELP compared to the soluble control or GLP1 alone. Adapted with permission from [368].

Fig. 20

RLP nanoparticle formation in response to various stimuli. (A-D) Representative TEM images of RLP nanoparticle formations at 25°C (A), 50°C (B), 65°C (C), and 85°C (D). The hydrodynamic radius of RLP nanoparticles is dependent on (E) RLP concentration, (F) salt concentration, (G) salt identity, and (H) pH. Adapted with permission from [385].

Fig. 21

Cell binding and uptake by RLP-ELP diblock nanomaterials. (A) Cellular uptake of RLP-ELP unimers, spherical micelles, and worm-shaped micelles with an integrin-targeting Fn3 protein domain. The increased avidity and worm-like structure of the micelle promoted its ability to enter the cell. (B) Shape-dependent avidity of RLP-ELP diblocks. Multivalency increased the affinity of the nanoparticles for its target by decreasing the off-rate. Adapted from [55].

Fig. 22

The fabrication and release profiles of redox-sensitive RZ10-RGD hydrogels. (A) Schematic of the crosslinking and degradation reactions of RZ10-RGD and DTSSP. Images of the crosslinked hydrogel in a non-reducing (left) or reducing environment (right). In a reducing environment (B), dextran release was not MW-dependent. In a non-reducing, PBS environment (C), dextran release was dependent on MW. Adapted from [395].

Fig. 23

(A) Doxorubicin-triggered self-assembly of SELP nanoparticles (B) Delivery of SELP-encapsulated DOX to HeLa cells at 40 min and 4 h. SELP encapsulation improves cell uptake and drug accumulation in the cytoplasm. Adapted from [362].

Fig. 24

Adenovirus delivery by SELP hydrogels. (A) Ad.GFP was released from a 4% SELP hydrogel over the course of 28 days. (B) GFP expression in tumor cells receiving Ad.GFP or Ad.GFP mixed with SELP. Panels a-d show GFP expression 3, 7, 11 and 15 days after injection. Adapted from [405].

Fig. 25

SAGE delivery with SELP hydrogels for the treatment of radiation-induced proctitis (RIP). (A) A schematic of the treatment platform. The glycosaminoglycan (GM-0111) was mixed with SELP and rectally delivered to a murine model for RIP. The injectable SELP solution forms a solid hydrogel upon administration to slowly release GM-0111. (B) Representative fluorescent micrograph images of rectal tissue 3 and 12 h after treatment with GM-0111 loaded SELP or GM-0111 alone. GM-0111 accumulation is enhanced and prolonged when delivered with the SELP hydrogel. Adapted from [410].

Fig. 26

XTENylation of therapeutics for improved pharmacokinetic properties. (A) Design and production of XTENylated protein drugs. A plasmid is designed such that the gene encoding the drug is fused to XTEN for recombinant expression (B) Pharmacokinetic profile of XTENylated exenatide (E-XTEN) delivered intravenously or subcutaneously to cynomolgous monkeys (C) A single injection of E-XTEN protected mice from a glucose challenge 48 h post administration. Adapted from [411].

Fig. 27

PASylation of therapeutics for improved pharmacokinetic properties. (A) Pharmacokinetic profile of recombinant and PASylated IFN in BALB/c mice. The number within the parentheses in the PASylated versions indicates the length of the PAS peptide. (B) Pharmacokinetic profile of recombinant and PASylated hGH injected intravenously or subcutaneously. Adapted from [426].