SerializationException: Type UnityEngine.UI.Button is not marked as Serializable. Solution

Hi, Im a beginner to Unity3d and C#, I'm inserting the cube and sphere when the toggle is on and i want to save and load the scene. hence , i tried the following code and i got a serialization exception.I'm unable to fix the serialization exception, could someone please help. I'm trying to save the scene to the file and load from the file. I'm attaching the following code below, please help.

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 using System;
 using System.Runtime.Serialization.Formatters.Binary;
 using System.IO;
 
 
 public class spawn : MonoBehaviour 
 {
     public static spawn control;
     public GameObject user1_cube;
     public Button Savebtn;
     public Button Loadbtn;
     public Button cube_insert;
     public Toggle cubeToggle, sphereToggle;
     public RaycastHit hit;
 
     void Awake()
     {
         if (control == null)
         {
             DontDestroyOnLoad(gameObject);
             control = this;
         }
         else if (control != this)
         {
             Destroy(gameObject);
         }
     }
     void Start()
     {
            demo();
     }
     void demo()
     {
         cubeToggle = GameObject.FindGameObjectWithTag("cubeToggle").GetComponent<Toggle>();
         sphereToggle = GameObject.FindGameObjectWithTag("sphereToggle").GetComponent<Toggle>();
         Savebtn = GameObject.FindGameObjectWithTag("Savebtn").GetComponent<Button>();
         Loadbtn = GameObject.FindGameObjectWithTag("Loadbtn").GetComponent<Button>();
 
        
     }
    
     void Update()
     {
         if (cubeToggle.isOn)
                 {
                     if (Input.GetButtonDown("Fire1"))
                     {
                         
                         var mousep = Input.mousePosition;
                         mousep.z = 4.0f;
                         var objectpos = Camera.main.ScreenToWorldPoint(mousep);
 
                         GameObject SpawnLocation;
 
                         SpawnLocation = (GameObject)Instantiate(GameObject.CreatePrimitive(PrimitiveType.Cube), objectpos, Quaternion.identity);
                         
                     }
                 }
                 
                 if (sphereToggle.isOn)
                 {
                     if (Input.GetButtonDown("Fire1"))
                     {
                         
                         var mousep = Input.mousePosition;
                         mousep.z = 4.0f;
                         var objectpos = Camera.main.ScreenToWorldPoint(mousep);
                         GameObject SpawnLocation;
                         SpawnLocation = (GameObject)Instantiate(GameObject.CreatePrimitive(PrimitiveType.Sphere), objectpos, Quaternion.identity);
                     }
                 }
 
         Savebtn.onClick.AddListener(delegate { Save(); });
         Loadbtn.onClick.AddListener(delegate { Load(); });
     }
 
     public void Save()
     {
         BinaryFormatter bf = new BinaryFormatter();
         FileStream file = File.Create(Application.persistentDataPath + "/playerInfo.dat");
         PlayerData data = new PlayerData();
         data.cube_insert = cube_insert;
         data.cubeToggle = cubeToggle;
         data.sphereToggle = sphereToggle;
         data.Savebtn = Savebtn;
         data.Loadbtn = Loadbtn;
         bf.Serialize(file, data);
         file.Close();
     }
 
     public void Load()
     {
         if (File.Exists(Application.persistentDataPath + "/playerInfo.dat"))
         {
             BinaryFormatter bf = new BinaryFormatter();
             FileStream file = File.Open(Application.persistentDataPath + "/playerInfo.dat", FileMode.Open);
 
             PlayerData data = (PlayerData)bf.Deserialize(file);
             file.Close();
 
             data.cube_insert = cube_insert;
             data.cubeToggle = cubeToggle;
             data.sphereToggle = sphereToggle;
             data.Savebtn = Savebtn;
             data.Loadbtn = Loadbtn;
 
         }
     }
 }
 
 
 [Serializable]
 class PlayerData
 {
     public Button cube_insert;
     public Toggle cubeToggle, sphereToggle;
     public Button Savebtn;
     public Button Loadbtn;
 }