Lithium chloride (licl)

Calcium chloride and lithium
chloride (∼99% anhydrous) were obtained from Sigma-Aldrich.
Sodium Alginate (SA, ≥99% with M/G = 1:2, 1:1, and 2:1) was
obtained from Shanghai Macklin Biochemical Co., Ltd. The following
chemicals were used for graphene oxide (GO) preparation: 99.9% metals
basis–10 mesh natural graphite flakes from Alfa Aesar (Germany),
potassium permanganate (99% KMnO₄) from Fisher Scientific
(USA), hydrogen peroxide (35% H₂O₂), and various
acids, namely, sulfuric acid (97% H₂SO₄), phosphoric
acid (85% H₃PO₄), and hydrochloric acid (37%
HCl) from Merck (Germany). Ammonium persulfate, pyrrole, lithium chloride,
and HCl were acquired from Sigma-Aldrich and used for the preparation
of polypyrrole doped with chlorine (PPyCl).

Copper(I) oxide (cuprous oxide, Cu₂ONPs) and copper(II) oxide (cupric oxide, CuONSs) nanostructures
(NSs) were prepared by chronoamperometry (at room temperature using
a VoltaLab potentiostat PGZ301 and at a constant electrode potential
of 0.8 V for 4 h).^{51 (link),52 (link)} 0.1 M aqueous solution of lithium
chloride (LiCl; from Sigma-Aldrich) was freshly prepared and used
for CuONS synthesis, while an ethanolic LiCl solution with 10% water
was freshly prepared and used for the synthesis of Cu₂ONPs.
The electrochemical treatment was carried out under an inert atmosphere
by slowly bubbling the solution with argon gas in a conventional three-electrode
cell with a platinum wire as a counter electrode and an Ag/AgCl (1
M KCl) electrode as a reference electrode (the potential is indicated
against this electrode). A copper rod served as the working electrode.
Before electrochemical treatment, metallic copper (99.99% Cu) was
polished with sandpaper to reduce the grain size and then purified
in anhydrous ethanol (99.8%; from Sigma-Aldrich). The precipitated
product was in the form of orange Cu₂ONPs and brown CuONSs.

Suspensions
of Ti₃C₂T_x MXene nanosheets were synthesized using an etching bath made
of hydrofluoric acid (HF, VWR Chemicals), hydrochloric acid (HCl,
Sigma-Aldrich), and deionized (DI) water (Millipore, resistivity of
18 MΩ cm) to selectively etch away the Al layer from the parent
Ti₃AlC₂ MAX phase. In a high-density polyethylene
(HDPE) bottle, 2 g of Ti₃AlC₂ powder (<40
μm in particle size, Carbon-Ukraine Ltd.) was added to the premade
etchant solution (20 mL) and left for stirring at 40 °C for 16
h. Following the etching, the obtained suspensions of exfoliated MXene
nanosheets were carefully washed in DI water through several rounds
of centrifugation and decantation until a pH value of ca. 6 was attained.
Delaminated MXene nanosheets were then obtained using lithium chloride
(LiCl, Sigma-Aldrich) as an intercalant. Afterward, the dispersion
of LiCl-intercalated Ti₃C₂T_x nanosheets was washed once with DI
water, once with a DI water–methanol mixture (each 50 vol %),
and then washed twice with methanol (anhydrous, 99.8%, Sigma-Aldrich)
through centrifugation. Finally, the supernatant (in methanol) containing
delaminated Ti₃C₂T_x nanosheets was collected and stored at ca. −15
°C for further use.

To prepare ZrO₂(-ACl)-A₂ZrCl₆ (A = Li or Na), a stoichiometric mixture of Li₂O (99.5%, Alfa Aesar) or Na₂O (80%, Sigma Aldrich, ~20% Na₂O₂), LiCl (99.99%, Sigma Aldrich) or NaCl (99.99%, Alfa Aesar), and ZrCl₄ (99.99%, Sigma Aldrich) was ball-milled at 600 rpm for 20 h in a ZrO₂ vial with ZrO₂ balls using Pulverisette 7PL (Fritsch GmbH) under Ar atmosphere. To prepare fluorinated HNSE ZrO₂-2Li₂ZrCl₅F, a stoichiometric mixture (Li₂O: ZrF₄: ZrCl₄ = 2: 0.5: 2.5) of Li₂O (99.5%, Alfa Aesar), ZrF₄ (99.9%, Sigma Aldrich) and ZrCl₄ (99.99%, Sigma Aldrich) was ball-milled under the same condition as for the conventional HNSEs. To prepare nM_yO_z-Li₂ZrCl₆ nanomixtures, M_yO_z nanoparticles were ball-milled at 600 rpm for 20 h in a ZrO₂ vial with ZrO₂ balls using Pulverisette 7PL (Fritsch GmbH). ZrO₂ (99.95%, 20 nm) and Al₂O₃ (≥95%, 50 nm) nanopowders were purchased from Avention and Sigma Aldrich, respectively. Fumed SiO₂ powders were obtained from Sigma Aldrich. For the preparation of Li₆PS₅Cl, a stoichiometric mixture of Li₂S (99.9%, Alfa Aesar), P₂S₅ (99%, Sigma Aldrich), and LiCl (99.99%, Sigma Aldrich) was ball-milled at 600 rpm for 10 h in a ZrO₂ vial with ZrO₂ balls, followed by annealing at 550 °C for 6 h under an Ar atmosphere.

The effects of LiCl and DKK1 on in vitro angiogenesis in the 3D collagen gel were determined by co-culturing GFP-ASCs and RFP-ECs, and the expression of angiogenic factors in a transwell model were determined by co-culturing hASCs and HUVECs; DMEM medium containing either 11.794 mmol·L⁻¹ LiCl (0.5 mg·mL⁻¹; Sigma-Aldrich) or DKK1 (100 ng·mL⁻¹; R&D Systems, Minneapolis, MN, USA) was used.
The effects of LiCl and DKK1 on in vivo angiogenesis in an implanted gel were determined using concentrations of 47.176 mmol·L⁻¹ (2 mg·mL⁻¹) per animal and 200 ng·mL⁻¹ per animal, respectively.