|Name||Charge Distribution||Amino Acid Sequence||Type|
CAPs are oppositely charged peptides (e.g. Ac-(LKLK)3-NH2 and Ac-(LDLD)3-NH2). The self-repulsion of each module prevents uncontrolled spontaneous self-assembly, while electrostatic interaction between positively and negatively charged peptides drive their co-assembly and lead to nanofibrillar architecture.
PAs typically consist of various structural domains e.g. a hydrophobic tail and a hydrophilic head, which allow formation of the aligned assembly into supramolecular structures and contribute to functional properties. The hydrophobic tail, for example, can consist of nonpolar amino acid residues (C,G,A,V,I,L,P,F) with different degrees of hydrophobicity while hydrophilic heads consist of positively charged (H,K,R) or negatively charged amino acid residues (D,E) in order to achieve good solubility in water. Examples of these kinds of PAs are: A3K, A6K, A9K, GnD2 (n=4, 6, 8, 10), and V6D.
More complex PAs have also been described. These typically consist of four domains: an alkyl chain as the hydrophobic domain, a short peptide sequence capable of forming beta-sheet structures, a region containing charged amino acids for enhanced solubility in water, and a bioactive epitope.
Figure: Structure of a PA consisting of four domains.
Applications of SAP Scaffolds in Regenerative Medicine
Numerous approaches in the application of SAP scaffolds in regenerative medicine have been reported. Among them are treatment options for spinal cord injuries, peripheral nerve transections, neurodegenerative diseases, burns, osteoarthritis, and enamel defects. Some examples are given in Table 2:
|Ac-(KLDL)3-NH2||Cartilage Repair||TGF-beta1 adsorbed to a Ac-(KLDL)3-NH2 peptide hydrogel stimulated chondrogenesis of equine bone marrow derived cells.||Kopesky, P. W. et al. (2014)|
|RAD16-I (PuraMatrix™)||Cartilage Repair||A unique composite scaffold was developed by infiltrating a three-dimensional (3D) woven microfiber poly-caprolactone (PCL) scaffold with the RAD16-I self-assembling nanofibers to obtain multi-scale functional and biomimetic tissue-engineered constructs.||Recha-Sancho, L. et al. (2016)|
|RGDS-PA + S(P)-PA||Bone Regeneration||Enhanced bone regeneration was linked to the presence of phosphorylated serine residues (S(P)) on the supramolecular nanofibers of the matrix. Animals treated with the matrix exhibited similar bone regeneration to those treated with allogenic matrix.||Mata, A. et al. (2010)|
|PFD-5 (Pro-Phe-(Asp-Phe)5-Pro)||Bone Regeneration||Amosi and co-workers could demonstrate that bone regeneration of the PFD-5 hydrogel might be further enhanced in compositions comprising beta-tricalcium phosphate (beta-TCP).||Amosi, N. et al. (2012)|
|C16–A4G3EIKVAV||Repair of Injured Spinal Cord||In vivo treatment with the SAP after spinal cord injury promoted regeneration of both descending motor fibers and ascending sensory fibers through the lesion site and also resulted in significant behavioral improvement.||Tysseling-Mattiace, V. M. et al. (2008)|
|Ac-RADARADARADARADA-NH2||Repair of Injured Spinal Cord||Transplantation of primate neural stem cells cultured in the SAP scaffold was efficient for repairing the injured spinal cord and for improving the motor function of spinal cord in rats.||Ye, J. C. et al. (2016)|
|P11-4 (Ac-QQRFEWEFEQQ-NH2)||Repair of Enamel Defects||Application of self-assembling peptide P11-4 can facilitate the subsurface regeneration of the enamel lesion by supporting de novo mineralization in a similar mode of action as has been shown for the natural formation of dental enamel.||Kind, L. et al. (2017)|
|RADA16, RADA16-FPG and RADA16-RGD||Skin Wound Healing||Adding different functional motifs to the RADA16 base peptide could influence the rate of proliferation and migration of keratinocytes and dermal fibroblasts. Relative to unmodified RADA16, the collagen I motif in RADA16-FPG (FPGERGVEGPGP) significantly promoted cell migration, and reduced proliferation.||Bradshaw, M. et al. (2014)|
SAPs are ideal building blocks for tissue engineering in regenerative medicine. They can be rationally designed and can be functionalized with motifs mediating for example cell adhesion. SAP hydrogels are used as carriers for cells and can contribute to tissue regeneration. Encapsulation of bioactive factors can be used to attract cells from the surrounding tissue, to promote cell survival and differentiation. The number of possible combinations and their compatibility with several tissue engineering technologies make them very attractive as substitutes for autologous and allogeneic tissue grafts. Bachem offers broad expertise and has shown proven success with over 165 related catalog research products. If you would like to explore more of these products, please click Regenerative Medicine.
L. Sun et al., Self-assembled peptide nanomaterials for biomedical applications: promises and pitfalls. Int. J. Nanomedicine 12, 73-86 (2017)
C.M. Rubert Perez et al., Mimicking the bioactivity of fibroblast growth factor-2 using supramolecular nanoribbons. ACS Biomater. Sci. Eng. 3, 2166-2175 (2017)
R. Pugliese and F. Gelain, Peptidic biomaterials: from self-assembling to regenerative medicine. Trends Biotechnol. 35, 145-158 (2017)
L. Kind et al., Biomimetic remineralization of carious lesions by self-assembling peptide. J. Dent. Res. 96, 790-797 (2017)
J.C. Ye et al., Using primate neural stem cells cultured in self-assembling peptide nanofiber scaffolds to repair injured spinal cords in rats. Spinal Cord 54, 933-941 (2016)
L. Recha-Sancho et al., Dedifferentiated human articular chondrocytes redifferentiate to a cartilage-like tissue phenotype in a poly(epsilon-caprolactone)/self-assembling peptide composite scaffold. Materials (Basel) 9, (2016)
A. Heidary Rouchi and M. Mahdavi-Mazdeh, Regenerative medicine in organ and tissue transplantation: shortly and practically achievable? Int. J. Organ Transplant. Med. 6, 93-98 (2015)
R. Ravichandran et al., Applications of self-assembling peptide scaffolds in regenerative medicine: the way to the clinic. Journal of Materials Chemistry B 2, 8466-8478 (2014)
P.W. Kopesky et al., Sustained delivery of bioactive TGF-beta1 from self-assembling peptide hydrogels induces chondrogenesis of encapsulated bone marrow stromal cells. J. Biomed. Mater. Res. A 102, 1275-1285 (2014)
M. Bradshaw et al., Designer self-assembling hydrogel scaffolds can impact skin cell proliferation and migration. Sci. Rep. 4, 6903 (2014)
H. Hosseinkhani et al., Self-assembled proteins and peptides for regenerative medicine. Chem. Rev. 113, 4837-4861 (2013)
J.B. Matson and S.I. Stupp, Self-assembling peptide scaffolds for regenerative medicine. Chem. Commun. (Camb) 48, 26-33 (2012)
N. Amosi et al., Acidic peptide hydrogel scaffolds enhance calcium phosphate mineral turnover into bone tissue. Acta Biomater. 8, 2466-2475 (2012)
J.B. Matson et al., Peptide self-assembly for crafting functional biological materials. Curr. Opin. Solid State Mater. Sci. 15, 225-235 (2011)
A. Mata et al., Bone regeneration mediated by biomimetic mineralization of a nanofiber matrix. Biomaterials 31, 6004-6012 (2010)
V.M. Tysseling-Mattiace et al., Self-assembling nanofibers inhibit glial scar formation and promote axon elongation after spinal cord injury. J. Neurosci. 28, 3814-3823 (2008)
P. Chen, Self-assembly of ionic-complementary peptides: a physicochemical viewpoint. Colloids and Surfaces A: Physicochemical and Engineering Aspects 261, 3-24 (2005)
G.A. Silva et al., Selective differentiation of neural progenitor cells by high-epitope density nanofibers. Science 303, 1352-1355 (2004)
Regenerative medicine aims to improve quality of life by repairing or replacing tissues or organs that are no longer functional with living working tissues or organs. In this emerging field, peptides are playing key roles in tissue repair and regeneration. For example, Cerapedics, an orthobiologics company, has developed P-15, a small synthetic peptide utilized as an attachment factor to stimulate bone healing. The company has launched i-FACTOR™ Peptide Enhanced Bone Graft, based on P-15 for use in cervical spine surgery (1). There are several peptide-based drug candidates in various phases of clinical development for use in regenerative medicine as shown in Table 2.
|Product Name||Active Ingredient||Condition Treated||Highest Phase||Companies|
|RGN-259||thymosin-β4||Dry Eye Syndrome(III), Neurotrophic Keratitis(III)||Phase III||ReGenTree and GtreeBNT|
|ARA290||cibinetide||Critical Limb Ischemia(II), Diabetic Neuropathic Pain(II), Neuropathy(II), Rheumatoid Arthritis(II), Memory Impairment(I), Neuropathic Pain(I), Acute Radiation Injury(PC), Insulin-Dependent Diabetes Mellitus(PC), Surgical Wound(PC), Diabetic Macular Edema(R)||Phase II||Araim Pharmaceuticals Inc|
|RGN-137||thymosin- β4||Epidermolysis Bullosa(II), Pressure Ulcers(II), Venous Stasis Ulcers(II), Burns(PC), Diabetic Foot Ulcer(PC)||Phase II||GtreeBNT|
|YH14618||--||Spinal Disorders(II)||Phase II||Yuhan Corporation, Ensol Biosciences Inc|
|RGN-352||thymosin-β4||Myocardial Infarction(I), Diabetic Neuropathy(PC), Epidermolysis Bullosa(PC), Inflammatory Bowel Disease(PC), Ischemic Stroke(PC), Multiple Sclerosis(PC), Renal Ischemia(PC), Traumatic Brain Injury(PC)||Phase I||RegeneRx Biopharmaceuticals Inc|
Phase III Candidates
Thymosin β-4 (Tβ4) is a 43-amino acid peptide that promotes cell migration, angiogenesis, cell survival and wound healing. ReGenTree and GtreeBNT are developing RGN-259 as Tβ4 containing ophthalmic products, the company’s candidate in Phase III development for the treatment of dry eye syndrome, neurotrophic keratopathy and other corneal disorders (2). RGN-259 is a Tβ4-based eye drop and this drug candidate has received orphan drug designation from the U.S. Food and Drug Administration for the treatment of neurotrophic keratopathy (3). In 2017, ReGenTree announced results from ARISE-2, its Phase III dry eye trial of RGN-259. The study showed improvement in the signs and symptoms of dry eye syndrome with RGN-259 versus placebo (4).
Phase II Candidates
Ariam Pharmaceuticals is developing ARA290 (cinbinetide) for the treatment of neuropathic pain in patients with sarcoidosis, acute radiation syndrome, cognitive impairment, critical limb ischemia, wound healing and rheumatoid arthritis. Cibinetide, the active ingredient in ARA290, is an 11-amino acid peptide that targets the innate repair receptor. This drug candidate has multiple orphan drug designations including US and EU orphan designation for the treatment of sarcoidosis, US orphan designation for the treatment of neuropathic pain in sarcoidosis and US orphan designation as a treatment to increase survival and improve functioning of pancreatic islets following transplantation (5). In May 2017, Araim Pharmaceuticals announced the publication of positive Phase IIb study results in small fiber neuropathy. The results demonstrated that ARA290 regenerates small nerve fibers and improves functional activity in patients (2).
RGN-137, another Tβ4 drug candidate which was developed by RegeneRx for the treatment of burns, diabetic foot ulcers, epidermolysis bullosa, pressure ulcers and skin ulcers is currently being developed by GtreeBNT after the execution of the license agreement between two companies in 2014. RGN-137 is a topical gel formulation of Tβ4 (6). Preclinical studies have demonstrated that RGN-137 affects several healing pathways including apoptosis, angiogenesis, collagen deposition and tissue inflammation. In 2017, GtreeBNT received permission from the U.S. Food and Drug Administration to start a Phase III trial of RGN-137 for the treatment of epidermolysis bullosa (2).
Yuhan Corporation is developing YH14618, a 7-amino acid peptide, for the treatment of degenerative disc disease (DDD). This peptide targets Transforming Growth Factor-β1 (TGF-β1) and prevents progression of disc degeneration by modulating TGF-β1 signaling. In 2009, Yuhan licensed YH14618 from Ensol Biosciences. In 2016, Yuhan completed a Phase IIb trial to evaluate the efficacy and safety of YH14618 in patients with DDD (2).
Phase I Candidates
RegeneRx’s second Tβ4 containing product candidate, RGN-352, is under development for the treatment of cardiac damage post-acute myocardial infarction, chronic heart failure and various nervous system disorders. RGN-352 is an injectable form of Tβ4. In 2017, RegeneRx announced results from the first human study with RGN-352 following a heart attack demonstrating that Tβ4 has potential clinical benefits in repairing and regenerating damaged tissue (3).
Regenerative medicine may have a bright future in addressing unmet medical needs. Peptides drugs are under development for a wide range of indications involving protection, repair and regeneration. To support researchers and organizations working in the exciting field of regenerative medicine, Bachem offers a variety of catalog peptides such as nanotube-forming products, adhesion peptide sequences, natriuretic peptides and more at shop.www.bachem.com. In addition, Bachem offers custom peptide synthesis, production of peptide-based new chemical entities and generic active pharmaceuticals ingredients.
(1) Cerapedics Receives FDA Approval for i-FACTOR™ Peptide Enhanced Bone Graft in Cervical Spine Surgery, PR Newswire (2015)
(2) Medtrack (2017)
(3) GlobalData (2017)
(4) ReGenTree Announces Results of ARISE-2 Dry Eye Trial (2017)
(5) Araim Pharmaceuticals’ Cibinetide (ARA 290) Regenerates Small Nerve Fibers and Improves Neuropathic Clinical Symptoms in the Orphan Disease of Sarcoidosis, PR Newswire (2017)
(6) RGN-137, RegeneRx (2016)
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